Implicit rules with Makefile

In my ongoing quest to make my builds less complex and faster, I've been going through my Makefiles and trying to learn as much as possible to simplify it and leverage Make as much as I can. To that end, I discovered something incredibly useful today that I suppose I would have known had I taken the time to read the man page for Make:

make -p

This command will list all of the implicit rules for make, which you can then use to optimize the living crap out of your Makefile.

Installing NTP on an Ubuntu server

NTP is used to synchronized time between machines. You can read the Ubuntu HOWTO here.

Installing a TFTP server using xinetd on Ubuntu

I recently had need to redo an old server that had been running an ancient Gentoo installation for which there was no longer a software upgrade path, so I chose to install Ubuntu on it. Part of the requirements of the server were that it runs a TFTP server for hosting files for configuring embedded devices. I had previously found an article on how to setup TFTP through inetd, but I could find it, so I'm cobbling this tutorial together from various sources.

1. # apt-get install xinetd tftpd
2. Ensure that the following lines are in the /etc/services file:
1. tftp     69/tcp
2. tftp     69/udp
3. Open the /etc/xinetd.d/tftp file (create it if it doesn't exist) and ensure that it contains the following:

   # default: off
   # description: The tftp server serves files using the Trivial File Transfer \
   #    Protocol.  The tftp protocol is often used to boot diskless \
   #    workstations, download configuration files to network-aware printers, \
   #    and to start the installation process for some operating systems.
   service tftp
   {
       socket_type     = dgram
       protocol        = udp
       wait            = yes
       user            = root
       server          = /usr/sbin/in.tftpd
       server_args     = -s /tftpboot
       disable         = no
   }
   

4. # /etc/init.d/xinetd restart

5. Test the server:# tftp localhost

   tftp> get hello.txt
   Received 23 bytes in 0.1 seconds
   tftp> quit 

You should now be good to go. The (abridged) instructions for this were retrieved from this article.

Digging into Raspberry Pi: Part 2

So, further into my quest to build a control system with the Raspberry Pi, I've been looking around at ways to have simple input from the user for a simple system. The first thing that came to my mind was using an Xbox controller to provide input from the user:

• It's simple for the user to use, and given that many people grew up with game consoles, it'll be intuitive and not require retraining the user.
• The Xbox controller plugs into USB and should therefore provide an easy way to integrate a controller for my system.
• The command to download joystick support for the Raspberry Pi was dead simple: 
• sudo apt-get install joystick

The post located here also shows some options for the joystick on the Raspberry Pi. I'll post more information as I learn how to use the library to access the device.

Digging into Raspberry Pi

I've recently purchased several Raspberry Pi boards so that I could use them with the RasPlex distribution to run Plex clients and connect them to my TVs and stream media from a central box in my house. However, I've now realized that with their ability to output to HDMI by default, I can use them as video controllers for projects at work. On my blog I'm going to document my experiences with the Pi, mostly as a list for me to follow if I ever have to recreate my work.

Today, I started off by doing the following :
1. Running NOOBS
2. Installing Raspbian
3. Used 'sudo apt-get install fluxbox' to install the Fluxbox window manager.
4. 'touch ~/.xsession' and 'vi ~/.xsession' and appended 'fluxbox' to the end of the file to start fluxbox when X starts.

Converting a .cer and .pvk to a .pfx file

The Windows SDK comes with a built-in tool for performing this conversion, the details of which you can find here. The command you'll need looks something like the following :

pvk2pfx /pvk MyCert.pvk /pi inputpassword /pfx MyCert.pfx /po outputpassword /spc MyCert.cer

Journey to robust windows services: killing a service that failed during OnStartup and now won't stop (even though Stop() has been called)

I've found that sometimes I don't exactly get my service configuration right the first time, and this can cause a failure when calling OnStartup. As a result, when I call Stop() during the exception handling in OnStartup(), the service gets stuck in the 'Stopping' state in the services manager. Here's a quick command line to help you out with that :

TaskKill /F /FI "Services eq [service name as diplayed in the service's properties]"

This will get your process knocked off so that you can resume debugging and building.

System.ArgumentException: Unable to find the requested .Net Framework Data Provider when using SQLite with MSTest unit tests in Visual Studio 2012

I recently encountered the exception in the post title while migrating solutions from Visual Studio 2010 to Visual Studio 2012. Going back and forth between versions, the problem only occurred for me in Visual Studio 2012, it otherwise did not appear in 2010. I ran across this post on StackOverflow about another developer in a similar circumstance, but I didn't want to depend on whatever machine I was using having the SQLite Db Provider installed in the GAC, so I chose a different route: I added [DeploymentItem]s for each of SQLite.Interop.dll, System.Data.SQLite.dll and System.Data.SQLite.Linq.dll to the top of each of my test suites that require them.  It's perhaps not an ideal solution, but it does seem to be the most pragmatic one for my circumstances.

Journey to robust web services: Fixing an error 404.3 message in IIS 7.0 / 8.0

I've recently had to go out of town, and only had my personal laptop to take with me. I usually develop in a Windows 7 environment with IIS 7.0 / IIS Express 7.5, but my laptop is Windows 8, so of course I have to go through the process of setting up my development environment all over again. One of the common errors I see when setting up a new environment is error 404.3: Not found. I run into it over and over again and when I fix it, it seems like such a trivial thing and I never remember to write down the fix to reduce my setup time in the future. Today that changes. The problem can be caused by a couple of things:
1) You don't have the application setup in IIS. You need to setup the application in IIS, *and* you need to point it to your web project directory.
2) You don't have all the requisite components installed in IIS. In order to properly install WCF, you must have IIS installed, you must have ASP.NET installed, and you must have WCF registered. Up to Windows 7 / .NET 4.0, this means you must have, at some point, run aspnet_regiis.exe -ir. On Windows 8, this means you must have installed ASP.NET 3.5 / 4.5, and installed HTTP activation for each (as well as corresponding activations for any other protocols such as net.tcp.

Journey to robust Windows Services: Overriding the default web site when deploying your applications from the command line

I recently ran into a problem where I wanted to deploy a new application to the default web site on an old IIS 6 instance via MSDeploy on the command line from my build machine. Unfortunately, it decided to deploy the application in a folder immediately underneath the default web site, rather than as the default website itself. This post on the IIS forums provided the solution.

Journey to robust Windows Services: NHibernate throws with System.InvalidOperationException: Unable to generate a temporary class

Recently I've been trying to deploy a new web application to an old machine running Windows Server 2003 (not by choice). When I would start the application, NHibernate would thrown in its class constructor with a message along the lines of :

System.InvalidOperationException: Unable to generate a temporary class (result=1).
error CS2001: Source file 'C:\WINDOWS\TEMP\wz58eig4.0.cs' could not be found
error CS2008: No inputs specified

The problem was caused by the fact that the user under which I was running the application didn't have access to the 'C:\Window\Temp' folder where the temporary folder was being created. The solution was simple: update the security settings of that folder to allow Read and List for the Users group. The idea was given to me by answers to this question on Stack Overflow.

How to fix the ugly ass Ubuntu boot splash OR Damn, Ubuntu, you ugly

TL;WR: http://news.softpedia.com/news/How-to-Fix-the-Big-and-Ugly-Plymouth-Logo-in-Ubuntu-10-04-140810.shtml

If you've had Ubuntu for a while and you've got an nVidia video card, chances are you've got the ugly ass default boot screen. Fortunately, you can fix this. You just need to follow the instructions above. I hope you're comfortable with the command line.

Changing the password complexity requirements on Windows Server

To change the password complexity requirements on Windows Server (2008 at least) (for whatever reason), do the following :

Start -> Run -> gpedit.msc -> Computer Configuration -> Windows Settings -> Security Settings -> Account Policies -> Password Policy

Then in the right-hand policy pane, set 'Password must meet complexity requirements' to 'Disabled' (right-click -> Properties)

Journey to robust windows services: Service could not be installed. Verify that you have sufficient privileges to install system services

This is an annoying and almost entirely useless error. It can be caused by any number of things. However, in my case today, it was caused by the fact that the EventLog Source hadn't been created when I tried to install my Windows Service using the WiX installer that I had developed (which it turned out wasn't quite complete). Fortunately, WiX (at least as of 3.5) has built-in support for creating Windows Event Log sources as part of the installation process. Fortunately, I was able to rely on this article on stackoverflow.com to guide me through the process. The gist of the article:

1. Add the "http://schemas.microsoft.com/wix/UtilExtension" namespace to your .wxs file root XML element
2. Add a util:EventSource Log="Application" Name="MyServiceLogSourceName" EventMessageFile="%SystemRoot%\Microsoft.NET\Framework\v2.0.50727\EventLogMessages.dll" element to each component which requires an Event Log source
3. Problem solved

Journey to robust windows services: debugging your WiX custom actions

I've recently had some trouble getting WiX custom actions to work, and after searching around for a while, I found this article. It gives the reader two options for how to debug WiX custom actions, but I had to use both in combination to get it to work. I'll repeat the steps here, just in case the link goes stale:

1. Follow all the necessary steps to create a WiX setup project, along with a separate Custom Action project (available as a project type in the New Project dialog in Visual Studio 2010+ with WiX 3.7)
2. After you've created your custom action method and gotten the project building, add System.Diagnostics.Debugger.Launch(); at the beginning of your custom action method. This will kick the custom action into the debugger so that you can debug it (assuming you've got the wixpdb in the same directory from which you launched the installer).
3. Go to Control Panel -> System -> Advanced System Settings -> Advanced (tab) -> Environment Settings (button) -> System Variables (group) -> New .... (button) 
4. In the dialog that comes up, create a new variable called 'MMsiBreak' (without the quotes) and give it the value of your custom action method (e.g. MyCustomActionMethod)
5. Now run the debug version of your installer and it should get kicked right into your method and allow you to debug your custom action.

Journey to robust windows services: creating custom actions for your WiX installers

I've lately been trying to update my WiX installers to perform custom actions so that I can do some security configuration of my applications after they're installed. I got started with this article on CodeProject, but it was missing some information. Apparently, in addition to creating the separate project for the CustomAction DLL, you need to include as part of that assembly a CustomAction.config file with the following contents:

xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup useLegacyV2RuntimeActivationPolicy="true">
        <supportedRuntime version="v2.0" />
        <supportedRuntime version="v3.5" />
        <supportedRuntime version="v4.0" />
    </startup>
</configuration>

But what really got the thing working was targeting the CustomAction DLL to .NET framework v3.5, rather than 4.0 because I was getting some bad image format exceptions when trying to run it. Thankfully I found the MSDN article on enabling MSI logging. These two articles on stackoverflow.com also really helped out.

Journey to robust web services: installing a WCF 4.0 application on IIS 6.0

Due to budget and other constraints, I'm unable to get my hands on the latest and greatest software for running a WCF application I've been working on, so I'm forced to use what my company's got: Windows Server 2003 and IIS 6.0. Suffice it to say that working with these old bits of software are less than ideal. However, I'm stuck with it. So, moving forward, here's some of the things I found while working on the application:

1. There's no easy way to set certain items in the registry for the Network Service user. (Sorry, for various reasons, I can't elaborate on that statement.)
2. Due to (1), I've decided to run my application as a custom normal (non-Administrator) user that I've created. However in order to use this user with IIS and its applications, certain steps must be taken.

Using a custom user to run an IIS 6.0 application

The following are pre-requisites in order to be able to use a custom user to run an IIS 6.0 application:

• The user must have already been created and should have absolutely the least number of privileges possible.
• Thanks to this question on Stack Overflow, the following must also have the following:
• The "Log on as a service" right (Start -> Control Panel -> Administrative Tools -> Local Security Policy -> Local Policies -> User Rights Assignment -> Log on as a service)
• "Access this computer from the network" (similar location as in the step above)
• "Deny logon locally"
• "Log on as a batch job"
•  "Read & Execute", "List Folder Contents" and "Read" access to the file system that underpins the web site/application
• Thanks to this troubleshooting article on MSDN, I also found out that the user must be part of the "IIS_WPG" group.

I now have other problems to worry about with this application, but at least now I know that they're not related to how I'm running the application in IIS.

Journey to robust web services: apparently we shouldn't use 'using'

I recently stumbled across an article stating why we shouldn't use the 'using' keyword with WCF services, and I found it rather interesting. I'd have to re-read it, and re-evaluate it, before I use it but you can read the blog post on the original site.

Journey to robust webservices: kickstarting use of certificates phase II: using certificates for client authentication

There are a number of means of authenticating users, and one of the most secure is via a certificate. This article on CodeProject provides a start. Unfortunately, the article doesn't really mention a few things:

1. Depending on how you ran the tools, you may have inadvertently run the commands it gives you as an administrator. I ran them in a console that I already had open that was running as administrator, so they were installed as administrator, and I also happened to have been running in Visual Studio as an administrator at the time, so everything happily worked. Then when I rebooted my machine this morning and was running as a normal user, nothing worked, and I wasted over an hour trying to figure out why. That was why. Regardless of how you generated and installed the keys, you should go and explicitly grant permissions on the key to the users you want to have access to them. On the Microsoft website, there is a bundle of WCF samples (which you can find here). Included in the samples is a tool called FindPrivateKey. Download the samples, compile the program, and use it to find the key that you just generated. You'll need a command similar to the following : "C:\Samples\WCFWFCardSpace\WCF\Tools\FindPrivateKey\CS\bin\FindPrivateKey.exe My LocalMachine -t "28 ce e3 2c 7e 05 3a 97 a0 b4 92 fd d5 b0 f9 de 0e 4c 2e 4b"" where the value in quotes is the thumbprint of the non-signing (client) key you generated in the instructions from the article. Once it spits out the location of the file, you'll need to go and alter its permissions to allow whatever user your server / client application is running under access to the file.
2. Depending on the binding you're using with WCF on the server side, you may need to have a certificate with full chain trust on the IIS server (or other?) in order to use the binding (*cough* basicHttpBinding and any other transport-only security bindings *cough*). With that in mind, after you've generated the certificates in the article, while you're in the certificate manager MMC snap-in, you'll also need to copy (not move) the IIS developer certificate used in IIS to the "Trusted Root Certification Authorities" store.

Journey to robust web services: kick starting use of credentials and certificates for message security, phase I

As any sensible developer of a large scale system knows, security is paramount. Therefore, encryption of sensitive data is an absolute must, encryption of all data is recommended, depending on the field in which you're working. Encryption with WCF is baked in, and is relatively straight forward to setup, though there are a number of important details to which attention must be paid. The steps are somewhat different depending on whether you're using IIS or a self-hosted service (e.g. in a Windows Service).

If you're using a Windows Service, you'll need to perform the following steps to get started:

1. Generate a self-signed certificate (which can be done in the Windows Control Panel)
2. Configure the port to which you're binding the service with the certificate you've just generated, according to this MSDN article. 
3. [to be continued]

If you're using IIS, getting started in a development environment is somewhat simpler.

1. Generate a self signed certificate with IIS. In most cases, IIS will have a developer certificate already installed that you can use.
2. Retrieve the thumbprint of the certificate. You'll need this in order for your application to be able to find it at runtime. WARNING: Don't just copy the thumbprint out of the certificate properties window in IIS, because there are non-printing characters in the text control that will cause you problems when you try to paste the thumbprint into your Web.config file. Write them out by hand.
3. There are two methods you can take for making the certificate available to your WCF service:
1. Follow the guide here if you want to make the certificate available to your application by code.
2. Use the information on this page to create a element underneath a configuration/system.serviceModel/behaviors/behavior/serviceCredentials element.

Journey to robust web services: debugging services and logging messages

One of the quickest and best ways to debug issues with the services you're developing is to log and trace all activity with WCF along with the messages being sent back and forth. This page on MSDN will provide you with the instructions required to setup logging and tracking for WCF.

Journey to robust web services: my clients are unable to connect!

I've been testing out some web services I've been working on extensively on my own machine, but the time has finally come where I want to start making clients that aren't running on the same machine. In one case, I have a WCF service running on Windows 7, but the client I want to connect to that service is running on Windows 8 on a separate machine. When I tried to connect, I would get a variety of errors, the most common of which being that the socket on the server was forcibly closed. I Googled around a bit, and the most common cause of this problem that I found was that the server's quota's were being reached and therefore the client was being rejected, however this shouldn't have been the case for me since there was no way my quota's could have been reached. After further research, I found that since I don't want security (yet), I had to apply some settings in order for clients that weren't on my localhost to connect. In order to allow external clients to connect, I had to change the following :

1. In my , I had to change my base address to use the network name of my computer (rather than localhost) in the base address URL.
2. In the net.tcp and ws2007HttpBindings for my services, I had to go to the the child element of the elements, and explicitly set mode="None" on those elements, otherwise they may assume some form of security by default depending on the type of the binding.

Now, I did mention above that I don't want to add security (*YET*) being the important qualifier of that statement. Security is of course always paramount, and should always be baked into a product as early as possible. As soon as I get to it, I'll add a post about all the steps required to add security to your WCF clients and services, along with links to the relevant MSDN articles (and any other useful ones that I may find.

Mono.Options installation, and getting StyleCop to ignore a file

I've recently discovered the Mono.Options library (available via NuGet) that lets you easily parse arguments passed into a program. Unfortunately, the ease with which a package is typically installed via NuGet does not apply to Mono.Options because it's a single .cs file that gets included in your project, rather than a signed assembly. This becomes an annoyance in projects where StyleCop is used to enforce coding standards. Fortunately, there is a way to get StyleCop to ignore specific files (rather than forcing me to tweak my StyleCop settings for the project) which I found out about here. The TL;DR for that article: edit your project file, and underneath the element for the offending file, insert a <ExcludeFromStyleCop>true</ExcludeFromStyleCop> element.

Creating a logging service using the Microsoft Enterprise Library Logging Application Block

As part of my recent foray into creating various Windows services, I've come across the need for logging (like all serious apps do) and decided to use the Microsoft Enterprise Library Logging Application Block. We used it at a previous company and it got very good reviews from the developers there who used it. Unfortunately, all of the tutorials out there are a bit useless when it comes to doing anything real with the Logging Application Block, like using custom configuration. Fortunately, it was easy enough to figure out how to get customized configuration of logging working just by looking in the assembly and writing some unit tests to experiment.

For my needs, I like to keep all of my configuration as compartmentalized as possible. To that end, I usually end up using .NET Configuration files on a per-assembly basis. Fortunately, this works very well with the Logging Application Block because you can configure logging with arbitrary Configuration files. To get custom logging working easily in Visual Studio, do the following:

1. Open Visual Studio (I'm using 2010)
2. Install NuGet from the Extension Manager, if you haven't already.
3. Install EnterpriseLibrary.Config from the Extension Manager if you haven't already.
4. Create your solution and project that requires logging.
5. If your project (web or application) comes with a .config file already (i.e. Web.config or App.config respectively) you can use that, otherwise, you can create an app.config file for the assembly in which you're creating your logging service.
6. Once you've figured out which app.config (or Web.config) file you're going to be using (i.e. the same assembly where you're placing your logging class, right click on the .config file. You should see an 'Edit configuration file' entry with an orange logo (provided by the add-in installed in Step 3 above).
7. Follow any other tutorial out there on the internet for configuring the Logging Application Block. (repeating such information here would be redundant and pointless). There's one such article here.
8. Now that you've got your configuration, create a class to be your logging service wrapper.
9. Figure out where your application config file is going to end up after your application is built.
10. In your logging service wrapper, create a Microsoft.Practices.EnterpriseLibrary.Common.Configuration.FileConfigurationSource, giving the configuration file path as the sole parameter to the constructor.
11. Create a new Microsoft.Practices.EnterpriseLibrary.Logging.LogWriterFactory, providing the FileConfigurationSource you just created as the sole parameter. You'll probably want to store this as a static object, because we only need a single factory.
12. For each instance of your logging service, use this static factory that you've created to create a LogWriter.
13. Implement whatever methods you need to wrap the logging service.
14. You're done.

Your code should now look something like the following :

    using System;
    using System.Diagnostics;
    using System.Diagnostics.CodeAnalysis;
    using System.IO;
    using System.Text;
    using Interfaces;
    using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;
    using Microsoft.Practices.EnterpriseLibrary.Logging;
    using Support.Extensions;

    /// 

    /// A logging services that uses the Microsoft Enterprise Patterns and 
    /// Practices library to provide logging support.
    /// 
    public class MicrosoftPracticesLoggingService : ILoggingService
    {
        /// 

        /// The log writer factory
        /// 
        private static readonly LogWriterFactory LogWriterFactory;

        /// 

        /// Initializes the  class.
        /// 
        static MicrosoftPracticesLoggingService()
        {
            string configFilePath = typeof(MicrosoftPracticesLoggingService).Assembly.GetCodeBaseFile().FullName + ".config";

            if (File.Exists(configFilePath) == false)
            {
                throw new InvalidOperationException(String.Format("Configuration file could not be found at '{0}'", configFilePath));
            }

            FileConfigurationSource configSource = new FileConfigurationSource(configFilePath);

            LogWriterFactory = new LogWriterFactory(configSource);
        }

        /// 

        /// The log writer used by this service to write to logs.
        /// 
        private readonly LogWriter logWriter;

        /// 

        /// Initializes a new instance of the  class.
        /// 
        public MicrosoftPracticesLoggingService()
        {
            this.logWriter = LogWriterFactory.Create();
        }

        #region Implementation of ILoggingService

        /// 
        [SuppressMessage("Microsoft.StyleCop.CSharp.DocumentationRules", "SA1604:ElementDocumentationMustHaveSummary", Justification = "InheritDoc")]
        [SuppressMessage("Microsoft.StyleCop.CSharp.DocumentationRules", "SA1611:ElementParametersMustBeDocumented", Justification = "InheritDoc")]
        public void LogException(Exception ex, string messageFormat, params object[] parameters)
        {
            if (ex == null)
            {
                throw new ArgumentNullException("ex");
            }

            if (messageFormat == null)
            {
                throw new ArgumentNullException("messageFormat");
            }

            StringBuilder messageBuilder = new StringBuilder();

            messageBuilder.AppendFormat(messageFormat, parameters).AppendLine();
            messageBuilder.AppendLine(ex.StackTrace);

            if (ex.InnerException != null)
            {
                Exception root = ex;

                while (root.InnerException != null)
                {
                    root = root.InnerException;
                }

                messageBuilder.AppendLine("Caused by:");
                messageBuilder.AppendLine(root.StackTrace); 
            }

            LogEntry logEntry = new LogEntry
                {
                    Message = messageBuilder.ToString(),
                    Severity = TraceEventType.Error
                };

            this.logWriter.Write(logEntry);
        }

        #endregion
    }

Journey to robust web services: debugging a net.tcp service

I'm creating a net.tcp-based WCF web service for use with my current project, and so far the learning curve hasn't been very shallow. I've just recently learned, thanks to this post on Stack Overflow, that the default ASP.NET application doesn't support the net.tcp protocol, so IIS must be used instead. With that in mind, I've decided to move on to just using the Web Service I'm creating through a Windows Service via a ServiceHost. However, I've now encountered some problems debugging the Windows Service startup. This page on MSDN contains links and instructions on how to debug the startup of a Windows Service. While attempting to install the Debugging tools, I encountered a failure trying to install them as part of the Windows 7 SDK. This page on Stack Overflow had a solution, but it wasn't quite complete. This page had the missing parts.

Journey to robust web services: configuring your WCF web service

WCF comes with a bunch of handy configuration tools.  You can find an introduction to them on the WCF configuration tools page on MSDN. Once you've created your WCF service project in Visual Studio, you'll need to use these tools to configure the service beyond a simple and basic test environment (which uses a Basic HTTP binding by default).

The specific tool mentioned on this page that you'll want to use is the Service Configuration Editor (svcconfigeditor.exe). This tool is used to edit Web.config files for WCF services. It comes with a handy wizard for adding a new service. When using this wizard, I ran into an error message similar to the following when trying to select the assembly I built containing my service: "Could not load assembly. This assembly is built by a newer runtime than the currently loaded runtime and cannot be loaded.". To solve this, I had to go and change the application configuration file for the program ("svcconfigeditor.exe.config" in the same directory as the program). I added the following under the root 'configuration' element:

 <startup useLegacyV2RuntimeActivationPolicy="true">
  <supportedRuntime version="v2.0" />
  <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/>
 </startup>

This will allow the program to run using your currently installed framework (mine happened to be 4.0).

Finally understand the purpose of event accessors in .NET

As most people who deal with .NET are aware, C# (and also VB.NET) have Properties and Events.  In the case of properties, there are property accessors (get and set) which you can leave to the compiler to define, or you can define your own custom accessors. Similarly, there are event accessors (e.g. add and remove) so that you can customize subscriptions to your event handlers. Until today, I never understood why, until I read the MSDN article on Advanced C#. The reason is explained near the end of the section called "Standard Event Pattern", and it's pretty simple and common sense: in classes where you have a significant number of events (e.g. WPF / Forms Controls) and only a few of them are likely to be subscribed to, you can achieve a smaller memory footprint by overriding the event accessors and placing the event subscribers in an internal IDictionary, rather than using compiler-generated event accessors. In the former case, you'll have to store only the subscribers + the dictionary, whereas in the latter case, you'll have to store the subscribers + n events, and the latter is likely to be far larger than the former.

Getting error message with XSD MSBuild task

Lately I've been getting the error message :

error MSB4018: Microsoft.Build.Shared.InternalErrorException: MSB0001: Internal MSBuild Error: xsd.exe unexpectedly not a rooted path

... while I've been building a project that uses that task in a pre-build step to generate code from XSDs. After googling around a little bit, I found the solution on this page. The gist of it was that xsd.exe wasn't in the PATH variable, and therefore Visual Studio couldn't find it. If anybody else has this problem, add this folder to your PATH:

C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin\NETFX 4.0 Tools

... or your system's equivalent, wherever the XSD.exe tool is stored on your system.

Debugging multiple processes and following the children in Eclipse Juno

I guess Eclipse has made it much easier in recent versions of Eclipse and CDT to debug multiple processes and have the debugger follow children. It was actually easier than I had thought it would be to get this functionality in Eclipse Juno. To do so, follow these steps:

1. Create your debug configuration, pointing to the project and program you require. 
2. Ensure that you setup your LD_LIBRARY_PATH in your environment variables as necessary.
3. (and here's the really important part) In the Debug Configuration, go to the 'Debugger' tab. You should see a groupbox called 'Debugger Options' containing (at least) two tabs: 'Main' and 'Shared Libraries'. On the 'Main' tab, ensure that you have 'Non-stop mode' and 'Automatically debug forked processes'. In order to get these abilities, you'll need to have both non-stop gdb and multi-process gdb
4. As a side note, you may need to also have your debug configuration pointed to a custom gdbinit command file with the following line:
• set follow-fork-mode child

This is admittedly a pretty high-level overview of how to get things going, but if I ever have any problems with this in the future, I'll post more details. Or if people ask me :P

Using key gestures with parameterized Commands in WPF is "broken"

Ok, it's not actually broken, it just doesn't work the way I wanted (or expected). Apparently, there's a very good article on why they don't work the way I expected. To be clear, the way I expected them to work was:

1. Define the command as a static RoutedUICommand and set the keyboard / mouse gestures I wanted on the command's InputGestures collection.
2. Use said command in MenuItems, Buttons etc.
3. Automatically have keyboard / mouse bindings setup everywhere (including the nice shortcut text on menu items in context menus / menu bar menus)

Turns out, no, and it's by design of the WPF team. See the article above for the explanation. At least now I know there's a good reason why it's not working, and I have a starting point for getting the key / mouse gesture functionality that I want.

Getting the proper Includes to show up in the project explorer in Eclipse with CDT with a cross-compiling project

I finally learned how, and it's thanks to an awesome question posted on stackoverflow.com .

"Network is unreachable" on an embedded box

We've been working extensively with embedded boxes lately trying to migrate our platform over. One of the programs we've been trying to migrate today was a simple announcer program that sends out a UDP broadcast. On our first go, the program wouldn't work, saying that the "Network is unreachable" when doing a 'perror' after the call to 'sendto'. After much experimentation with various network binding flags, etc, which took the whole day, I went into overtime trying to figure out the problem. Eventually, I got to the point where I inspected the routing tables of the embedded system and was shocked to find .... there was no routing table entry for the default gateway, i.e. 0.0.0.0 destination IP. I'm actually kind of ashamed of how long it took me to find this, but in my defense, I was dealing with a wild mixture of systems and had done a lot of network reconfiguration with the systems and some of the stuff was handled automatically for me by my Ubuntu box, which gave me some inconsistent results at times when experimenting.  For my own future reference, here's how I solved the problem:

• Run 'route -n'
• Ensure there's an entry that looks like the following :
• Destination: 0.0.0.0 Gateway: [the desired gateway, e.g. 192.168.10.1] Genmask: 0.0.0.0 Flags: UG, Metric: 0, Ref: 0, Use: 0, Iface: eth0 (or eth2, or whatever you may have)
• If the above entry doesn't exist, add it with the following command:
• sudo route add -net 0.0.0.0 netmask 0.0.0.0 gw 192.168.10.1 dev eth0

You should now have no problems with your UDP broadcasting. If you do, well, let me know how it goes, I'd love to hear your problem and your solution.

Synchronizing with a remote SVN repository

We recently had a double hard-drive failure on our RAID 5 on our main server at work, and we lost our stuff. Our primary backup method of that system had completely failed due to the incompetence of some of the staff in our parent company that was completely beyond our control. It's only by the grace of the fact that our IT guy had an extra weekly backup that we were able to recover as much as we were. That said, it brought to light the need to have our own extra backups of our source code because we can't rely on the people we're supposed to be able to rely on to do the backups for us. We're now going to be creating our own copies of the SVN server on a semi-daily basis, and I've found instructions on how to do it on this awesome StackOverflow post. I'm just sorry I didn't know about this sooner.

Cross-compiling libexpat (and other libraries)

So, lately I've been trying to cross-compile libexpat for a new board with a different architecture from what we typically use at work, and I've been having one heck of a time, until I finally got help online from my question at stackoverflow. Turns out, I just needed to be more specific about my host architecture in the configure command:

./configure --host=arm-none-linux --enable-shared CC=arm-none-linux-gnueabi-gcc CXX=arm-none-linux-gnueabi-g++ AR=arm-none-linux-gnueabi-ar RANLIB=arm-none-linux-gnueabi-ranlib STRIP=arm-none-linux-gnueabi-strip

I'm going to try similar recompilation with other libraries so that I can improve the functionality of our older systems as well.

Journey to robust Windows Services

Because I have the need for it in several projects, I'm going to be working with Windows Services implemented with .NET quite a bit in the next little while. That said, I'd like to refer to some resources for working with Windows Services:

• The MSDN page on creating windows services
• The MSDN page on debugging a Windows Service
• The MSDN page on installing and uninstalling Windows Services

Also, there are some issues that I ran into while working on my first service. I had originally planned to expose a WCF endpoint through WS-HTTP, however, I can into an unpleasant exception when I tried to do so: AddressAccessDeniedException. Apparently, the cause of this is the fact that http bindings are reserved for processes run as administrators. Fool me once, shame on me. In light of that fact, I'm switching over to using net.tcp for my local Windows Service-hosted WCF service. I'll post more here as I learn it.

Adding the Network Service account to the permissions for a file/folder/registry key etc

I'm currently developing a Windows Service that's to be run under the Network Service account (owing to the fact that it requires substantial network access). I'm just starting to learn how to program Windows Services, so this is very new to me. I just started developing a simple service to start, and when I followed the instructions on this MSDN page, I was surprised when, after trying to start my service, I got the error 005: Permission denied. I later found out that I needed to give the network service account to the folder from which the service was running, i.e. the debug output folder of my project. Doing this isn't as simple as setting the permissions for other users. To add the network service account to the permissions list in Windows 7, do the following :

1. Right click on the folder containing the service you want to debug, and go to Properties
2. Go to the Security tab, and under the box marked "Group or user names", click on Edit ...
3. Under the window that pops up, you'll see another box marked "Group or user names". Underneath that box, click on Add ...
4. In the "Select Users or Groups" dialog that pops up, click on the Advanced... button at the bottom left.
5. In the advance "Select Users or Groups" dialog that pops up, click on Find Now to find all the users, groups and built in security principals.
6. Once the search results are populated, scroll down and select "NETWORK SERVICE" (not "NETWORK") and click on Ok, then Ok again in the Select Users or Groups dialog.
7. One you're back to the Permissions window, ensure that you give the Network Service account Full Control over the folder in the Permissions box, then click Ok.
8. Click Ok one last time to close the properties for your folder, and you're done.

Wpf2WinRT: Bindings are not the same!

I've just learned something new about the bindings system in WinRT: they're not the same as Bindings in WPF. Check out the MSDN page for WinRT BindingMode, and you'll see that they're missing a value from WPF: OneWayToSource.

Migrating from WPF to Windows 8

As part of the ongoing development efforts at my company, I'm always researching the latest technologies and developments. My latest endeavour is researching Windows 8 and doing technical feasibility work to find out if it's right for us. On that front, I'm learning how to develop for the Windows 8 runtime in C#. I've got a lot of experience in WPF, and our current Line-Of-Business application is written in WPF, so I'm used to certain things, things which I'm finding no longer hold true in WinRT programming. For example, how resources such as strings are accessed in XAML. For WPF, if I wanted the internationalized string for a label, I'd do something like this : <Label Text="{x:Static resources:Messages.UserName}"/> However, the x:Static XAML extension no longer exists. Instead, you have to follow the *very different* ways of accessing string resources on this MSDN document, because the means of accessing resources for a WinRT application are both simpler (in some ways) and more robust, if a little bit confusing at first. For string (and even other resources, such as images) internationalization in WinRT, what you do is this: 1. Create a folder path for your strings: \Strings\en-US 2. Under the aforementioned folder, create a resources file named Resources.resw (not that it's not .resx, as with previous .NET applications written in Windows Forms, WPF and ASP.NET) 3. Add a new string with the Name "ApplicationName.Text". The ".Text" suffix is very important; you'll see why in a minute. 4. In your XAML, create a TextBox like this: <TextBlock x:Uid="ApplicationName" Text="" /> The Uid attribute is used for associating controls with resources, according to the MSDN link provided above, and the .Text suffix in the resource Name column, specifies the property to which the resource is linked. Honestly, I'm not sure I like the way this is going, but if it reduces code clutter, I'm willing to at least give this a try. We'll see how this pans out.

Finding the public key and public key token of an assembly for use with InternalsVisibleTo

It seems like one of the most common problems out there when it comes to testing and dealing with strongly-named assemblies is getting the public key and the public key token of a CLR assembly when you want to create test projects for that assembly. The quick and easy way: 1. Ensure that 'sn.exe' is in your path. If it's not, it's usually in the Windows SDK directory, typically in a folder like : C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin\sn.exe 2. Open up a command window, and navigate to the directory containing the snk you're signing your assemblies with. 3. sn -p my.snk Public.snk 4. sn -tp Public.snk ...and voila, the program will print out the public key and public key token to the screen for you. The reminder I found this at was here. After you've found the public key, you'll want to paste a line similar to the following in the AssemblyInfo.cs file of the project whose internals you wish to expose:

[assembly: InternalsVisibleTo("MyCompany.ProjectName.Tests,
PublicKey=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX")]

Changing the default URI of a WCF web service

I recently returned to one of my previous employers since they lured me away with a better employment offer than I was currently receiving. I'm now placed on a large scale project to revamp our equipment and our software, and improve our software services to the point where we have absolute control and communication with our software out in the field. To that end, I'm presently writing a service that our field personnel's laptops will use to communicate with our home office. I've decided to implement the service in WCF since I've got experience with it and it will be the quickest route to getting a working service deployed. There are other reasons for the choice, but we won't go into those at the moment. One of the things I had forgotten about was the best practice of changing the default namespace of the service away from tempuri.org. I found an article here to remind me of how to do it, so hopefully others will be able to find it as well.

Previews with a DataContext in WPF

Both the company I currently work for and the previous company I worked for use WPF extensively in some of their products. I recently ran across an incredibly helpful bit of functionality that aids in designing controls and forms on this blog. The TL;DR is that it lets you specify the data context that's supposed to be associated with a window / control, and lets you preview the control at design time using design data. This is useful because it lets you get an idea of what the control is going to look like with real data, and can be especially helpful when trying to size controls on a form, or seeing what lists are going to look like, and will be a real time saver because it means you no longer have to compile and start the application in order to view styles on things like DataTemplates.

Deleting more Subversion folders

Further to my previous post on deleting subversion folders with powershell, I recently had the need to do the same in bash on linux. Here's a useful little command :

find . -name .svn -exec rm -rf {} \;

Determining what ports Tomcat is running on

I've recently had problems connecting to a Tomcat server setup by another developer. In order to troubleshoot these problems, I wanted to use netstat to see what ports were being bound to, but apparently server sockets don't come up by default. If you really want to see what server sockets are in use on your machine, use the following :

netstat -lntp

The undocumented 't' option will cause netstat to show server sockets.

Event models in Silverlight vs WPF

To really understand the event model in Microsoft's Silverlight / WPF frameworks, you need to start off with a proper mental model. You can think of the root XML element in a XAML object as being at ground level. Each successive child XML element goes deeper into the ground. With that in mind, there's two terms that are used in both of these frameworks to describe how event handlers propagate between objects : Bubbling and Tunneling. With Tunneling, event handlers start at the root XML element, and "tunnel" deeper into the "earth" (your control stack) until they get to the original source of the element, which is your controls. With Bubbling, event handlers start at the original source of the element (your control which initiated the event), and then "bubble up" to the root control. We use the earth analogy because the terminology goes hand in hand with gravity : tunnelling follows gravity, like digging into the earth, and bubbling goes against gravity, like a bubble coming up to the surface from the bottom of the ocean. I never really had a clear mental model of the Silverlight / WPF event models until right now.

With all that said, there are some differences between Silverlight and WPF that turn out to be very important when it comes to implementing your event handlers, and maintaining compatibility between the two. The biggest difference is that WPF supports both Bubbling and Tunneling events, whereas Silverlights supports only Bubbling events. Keep this in mind if you're designing desktop applications that you might want to port over to web applications at some point

Holy crap, a Windows ramdisk program that works

In the past, I've had a bit of experience trying to install and run ramdisks in Windows XP, but I never found anything really good. Microsoft provided a ramdisk driver for Windows 2000 that one could get working in XP, but it wasn't really useful because it only provided a maximum of 32 MB of storage (Why ?!). I decided to revisit the issue of ramdisks at work today for Windows 7 because I wanted a way to speed up Visual Studio's caching and other operations (and Eclipse, but that's another matter). After searching around some more, I found a program called ImDisk. The installation is dead easy (if a little lacking in the notification department to tell you it's successfully installed). What's even better, you can make disks of arbitrary size, have it simulate various kinds of devices, and you can setup multiple ramdisks. The only catch is that you have to start the service in Administrator mode, and it's a bit more than trivial, though it is easy using the following steps :

1. Start -> All Programs -> Accessories -> Command Prompt -> Right-click -> Run as administrator
2. sc config imdisk start= auto (note the space between start= and auto, this got me the first time)
3. net start imdisk
4. Open up Control Panel -> ImDisk Virtual Disk Driver

... and have at it!

Editing your file system mappings for TFS paths

So, as you may or may not know, when using Microsoft Team Foundation Server for version control, TFS maps remote project paths into local file system patmhs for checkout, etc. As I learned today, there are times when you check out the wrong path, and/or map it to the wrong path in the file system. If you ever need to modify or just nuke your file system mappings in TFS, here's how you go about doing it :

Team Explorer -> Source Control (double click) -> Workspaces (dropdown) -> Workspaces ... 

Once you've selected your workspace in the dialog that comes up (you'll likely only have one anyway), click on :

Edit ... -> Working Folders 

... and then select the folder to file system mappings that you want to remove, or create whatever new file system mappings you want right there.

Starting a new job ... and a new philosophy

Ok, so I've left my previous employer and started at a new job. This means new domains of knowledge, new tools, and new people. My new employer is a Microsoft-exclusive shop, for almost every aspect of their software. If you've read this blog in any significant amount in the past, you'll know that I'm really not a Microsoft fan. In fact, I hate almost everything that's ever come out of Redmond, because for the most part it's deficient in how it's been engineered, and not as usable as other products out on the market (or even a lot of open source products). Therefore, the tone of this blog is probably going to change somewhat, and I'll be ranting and raving like a lunatic on things I'm learning about dealing with Microsoft products more often. It's going to be interesting.

Finally ... MySQL workbench sucks less

MySQL workbench has been out for quite a while, under the guise of the people at MySQL. For the longest time, I stuck to using just the individual MySQL Query Browser and Administrator because they weren't too bad, and there really wasn't anything out there that I liked much better for query browsing alternatives. I tried out the old Workbench back when MySQL was standalone, but it really wasn't a very positive experience, so I just dropped it.

However, lately, something drove me to search for better alternatives to the MySQL query browser again, and I don't even know why. In my Google search, the MySQL Workbench came up, and I saw that it was a very recent version that was a good .2 versions up from the last one I had used, so I figured I'd give it a try. The difference was startling. Not only did they completely revamp the interface (at least for the Mac) but the workbench was just generally much more reliable and performant than the old query browser. If you get the chance, give it a shot. The new integrated interface is much more user friendly, and there's a bunch of new "Copy to clipboard" snippets that I personally find incredibly convenient and useful.

Running multiple Tomcat 6 instances in Ubuntu, the quick and dirty way

Here's a quick list for running multiple Tomcat 6 instances on Ubuntu 10.04 :

• Copy the /etc/init.d/tomcat script with a new name in the same directory


• Update the NAME variable in the startup script with a name for the new instance that you want to run.


• Copy /usr/share/$(old)NAME to the (new) NAME you've just created, along with /var/lib/$(old)NAME and /etc/default/$(old)NAME


• Edit the server.xml file under /var/lib/$(new)NAME/conf/ and change all the ports (ie for shutdown, and all your Connectors) so that they don't conflict with the old instance


• Run /etc/init.d/$(new tomcat script name) start

You should now have a running, fully functional instance of Tomcat on the server, using a different port.

Quickly dropping all the tables in a MySQL database without dropping the database itself

I've recently come across a case where I need to drop all the tables in my database (ie effectively truncate the database) but MySQL has no built in command for doing so. This is where the magic of command lines becomes very useful. I found a great little trick here that will very quickly let you get rid of all that annoying data so you can load in new test data into your database :

mysqldump -u[USERNAME] -p[PASSWORD] --add-drop-table --no-data [DATABASE] | grep ^DROP | mysql -u[USERNAME] -p[PASSWORD] [DATABASE]

If you've got GnuWin32 or another set of GNU programs installed on your Windows box, you can even do this in Windows without even changing the syntax !

Quickly dumping a MySQL database out to a file

I've found that sometimes, I just need a quick and dirty copy of a database to test changes against, and it doesn't matter if the data is recent, or even consistent for that matter. That's where mysqldump comes in handy with the --single-transaction option. It can be used on a live database because it doesn't lock the tables and prevent your web application from continuing to insert, modify and delete new records. One example would be :

mysqldump -u myusername -h myhost -p --single-transaction mydbname | gzip > mybackupfile.20100803.sql.gz &

This can be made even quicker by combining this dumping into an SSH transfer to copy the output data to another machine.

Piping a MySQL database from one server to another

I know that there's a lot of great, wonderful things that can be done on-the-fly through SSH. It's one of the greatest tools out there for moving data or communicating between two machines. So I thought "Why not try to move my database in the fastest way possible via SSH?", and here's the command I found :

mysqldump -ux -px database | ssh me@newhost "mysql -ux -px database"

This is of course a very basic, stripped down version of the command, which I haven't tested yet, but it's a good start to what seems to be a very common problem among developers.

Converting Unix timestamps to something readable in Excel

Our company uses log files in our machines to log raw data in real-time so that we have a history of what's happened on jobs that can be analyzed and, if necessary, used to prove to inspectors that our machines are doing what they say they are. We have our own log file parsing and analysis package for performing various analysis, but sometimes we need to look at the raw signals themselves in the logs, and this is where Excel comes in handy. The timestamps that are put on the signals are Unix timestamps, so seconds since the Epoch (Jan. 1, 1970 at 00:00:00 hours), which are not very useful in Excel, because Excel has its own Epoch (Jan. 1, 1900). To make things just a little bit more complex, we have machines in different timezones, which we need to account for as well. Thanks to a post at this site, I managed to come up with a modified version of their formula that will convert the unix timestamps to Excel format, and adjust them for timezone offsets :

=(ROUNDDOWN(A10116,0) / 86400) + 25569 - TIME(6,0,0)

Coding for Effect vs Coding a Model

One of the software engineers I've worked with in the past has a very different way of doing things. He will take the most expedient way of implementing a particular piece of software in order to get the job done, always. Every time. (Admittedly, there is the odd time where this is the most effective means of doing software in order to get a job done, and potentially avoid getting fired, but that's for another discussion). The person in question takes no pride in his own work (by his own admission) and doesn't care about the quality of his work. Essentially, he codes with only the desired effect of his work in his mind. I've found that this way of doing things (while being faster) is a great way to introduce bugs and to cause problems later that arise as a lack of planning and forethought, ie lack of maintainability, inability to add features to the software.

Whenever I write my own software, I write it to model what's going on in a business or scientific process. (Really, isn't that what software's supposed to do ? ;P) I think about what's going on, and I try to model it in the software, taking into account all possible factors (or at least everything that reasonably occurs to me) that may influence the process. This typically results in a reliable system that very rarely breaks down. When a breakdown does occur, it's always been the result of something that I hadn't anticipated. I then go back to the software, and re-evaluate the model to see if there's something I need to change, and change it. This way of implementing software results in software that's easy to maintain, is (virtually) free of side effects, and can virtually eliminate undesired behaviour.

Working with CSV files in Excel the way you want ... rather than the way Microsoft tells you to by default

In both my current job and my past jobs, I've worked with CSV files in Microsoft Excel as a matter of necessity. Excel is just too useful not to use (OpenOffice has its own quirks, but that's for another post.) The only problem with Excel is that it formats fields automatically when you open a CSV file by double clicking on it or by going through the File -> Open option (or Ribbon -> Open in Office 2007 and later). Sometimes this is nice, but most times it's a pain in the ass, especially when you want to be able to save that CSV data right back out to CSV again. What happens is Excel converts the values to particular data types after introspecting the data in the cells. This is annoying and stupid, especially when you have financial, scientific and engineering data that's in a format that doesn't fit will into Microsoft's algorithm for dealing with numbers, dates, times, and currencies.

There is a way around this giant annoyance. Instead of taking the easy way of opening the file, you can open Excel directly, with a fresh spreadsheet. Then, on the ribbon, go to the Data tab, and click on the 'From Text' button. This will let you open a delimited text file, and treat it as a data source, and Excel will give you options for opening the file and how you want to deal with its contents. This is much better for dealing with the data, especially when dealing with tab-delimited files.

Background on the home search page ? WTF Google ?

Today I went to Google (as I do most days) to search for some stuff, but today when I got there, I was greeted with a horrible looking background on the search. My very first thought was "Did I just go to Bing by mistake ?", then I looked closer at the page and realized it was indeed Google. Needless to say, I was incredibly pissed. Why did Google change their signature search page ? It was great the way it was ! That was specifically why I went to Google. If I wanted to use a search engine that looked like a piece of shit, I'd use Bing. In my mind, this is nothing short of an epic fail on Google's part. And apparently, I'm not alone in this feeling.

My hatred of Microsoft is justified ... yet again

There are two different schools of thought when it comes to being a vendor of very large software used by millions of people :

1. Move your software forward as often as possible, even if a few customers have to suffer lack of backward compatibility


2. Move your software forward as little as possible, even if a few customers have to suffer lack of innovation

I've noticed from my own personal experiences that Apple tends to take the former attitude, whereas Microsoft tends to take the latter attitude. In the end, someone (probably you) is going to get screwed over at some point, it's just a matter of how you want it to happen. As a consumer, I generally like Apple products, so on my personal technology front, I choose the former. As a software developer, I'm forced by business constraints to accept the latter. The specific circumstances that bring me to mention this :

Today I was working with version 4.0 of the .NET framework, the very latest (and supposedly greatest) from Microsoft, along with the very latest version of their Visual Studio (2010) software. I'm also using these with WPF (the Windows Presentation Foundation) to create an application for my employer. For various reasons, I had to go back and refactor some old code, part of which required opening log files for viewing within the application. In order to open a file in WPF, you must use the OpenFileDialog class that comes with the Windows Forms library, which has been around since Windows 2000 (if not earlier, I'm admittedly not as familiar with the lifecycle of this technology as I could be). If you're a developer on the Windows platform, or even just an observant user, you'll have noticed that on the OpenFileDialog there's a Places bar on the left hand side of the dialog that provides common places for storing files, some of which are very general and will require some drilling down into subfolders to find what you actually want. I wanted to be able to add a place to this bar so that users of the application (company employees who work as technicians out on job sites) could have a direct link to the typical directory used to store log files on their machine.

It turns out that adding a folder to the places bar is obscenely difficult, and must be done through registry hacks. My question is this (directed squarely at the developers at Microsoft responsible for writing the GUI controls, specifically these dialogs) : what the hell was going through your head that would make you think that the way you've implemented these dialogs is a good thing ? It's obscenely hard on developers to customize the generalized tools that you've given them, and this in turn makes it hard on users of that software to use the software made by developers bound by these stupid and seemingly arbitrary constraints. I find myself growing increasingly frustrated by stupid decisions of the Microsoft developers that seem obviously poor when you look at them from the perspective of a framework user. These poor decisions are costing me a lot in terms of time I have to spent developing around these decisions and researching alternatives. It's now no wonder to me how other companies can make absurd sums of money off of controls designed as work arounds for the short-sightedness of Microsoft's developers, and frankly, it's quite depressing.

Fixing telnet disconnects

I've recently been working with a lot of embedded systems via telnet, and I'll frequently forget to disconnect my session before physically disconnecting the machine from my local LAN. Unfortunately, this results in telnet hanging the session, and me being unable to do anything else. Until now, I've just closed the window and opened another, but that became a pain in the ass, especially when I had to discard my (very useful) terminal history. Apparently, you can rescue a hung telnet session and avoid having to kill your terminal session by pressing Ctrl+5. This sends a signal to telnet to end the current session and return you to a prompt. Incredibly useful. Looks like there's a ton of other stuff where I found this useful tidbit.

Resolving slow SSH login times

At work, like most other organizations, we have a Linux server that we access via SSH. However, lately, I've found my use of it skyrocketing in order to test software, and log-ins and file copying have been very slow. In my efforts to find out why, I found out that sshd has in its configuration file a setting called 'UseDNS'. The default is 'yes', so even if this setting is commented out, it will try to perform reverse DNS lookups on the IP addresses of users logging in. This would be a bad thing for us, especially since we have this box locked down and unable to contact any DNS servers. After disabling DNS lookups, my login and file copy time dropped to near 0. I hope this helps somebody.

*EDIT:* I've also encountered this problem on the BeagleBone Black boards which I've recently acquired for use in a project.

Two bash functions that will make your software development life 10% easier

... if you use SSH to move between machines a lot. Which I do. I have several machines that I work on regularly, and a centralized development machine shared with others that I frequently have to exchange files with. The following two functions are the most useful two bash functions that you can put in your .bashrc file if you use SSH as much as I do :

function ssh-create-keys {
ssh-keygen -t rsa
}

function ssh-setup-on {
cat ~/.ssh/id_rsa.pub | ssh $1 "cat - >>.ssh/authorized_keys"
}

The first sets up an SSH key file for you in your home directory, This key file will be used to identify you on other machines, and can be used for various purposes on your local machine as well. The second function logs you into the machine determined by the username@anothermachine given as the first argument to the function, and adds your public key to the list of authorized keys for that machine.

Once you've run the first function, and run the second function to setup your public key on an account on another machine, you'll now be able to use SSH to log in and copy files freely with the account on the other machine without having to enter a password. While this is incredibly convenience, it also comes with a caveat : it's dangerous. If somebody other than yourself gains physical access to your machine and can log on as you, (or use your already logged on account), they can move to those same machines freely and perform possibly malicious actions, as you. Keep that in mind.

Copying files in linux

Lately I've been doing a lot of embedded development with Linux, and copying files between systems has been a bit of a pain. Fortunately, a combination of RSync and SSH solved my problems, with a command that lets me copy files from a directory on one system to a directory on another system, recursively with symlink preservation (and even duplication !) :

rsync -azuv -e ssh  user@systemaddress:~/path/to/dir/* .

WTF ?! Windows (as of Vista) no longer supports multiple different monitors!? WHY ????

Apparently, as of Windows Vista and later, Windows no longer supports multiple video cards that don't use the same driver!! Why ? I use a Radeon and a Matrox QID to drive 6 displays on my development box, and this just entirely fucks me over. At best, I can only use four of my displays now, and that's only going to be when Matrox gets off their lazy ass and releases a Windows 7 driver for their QID LP PCIe video cards. I'm so disappointed with what's a complete step backward for Microsoft. Epic fail, Microsoft.

Seeing where Perl looks for its modules on a system

Because we have very limited space on some embedded devices that we use that run Perl, we can only store a very few modules on these systems. This is a consequence of the fact that we run Busybox on these things, so by definition everything on these boxes is limited, if present at all. Therefore, we have to check and see if a module is available before we can use it in our code. Fortunately, there's a quick one-liner to see where Perl is looking for modules on a system :

perl -e'print join "\n", @INC'

I got this off a forum post from somewhere, and I'd post it here if I could find the link again. My apologies to the author of that forum post if they ever happen to run across this blog.

Embarking on a Perl journey

A long time ago, in a job far, far away, I had to deal with some Perl. I learned just enough to get me by for the duration of the task at hand, and then pretty much forgot everything I had learned. Now, at my latest job, I'm having to deal extensively with legacy systems which have a considerable amount of logic written in Perl that needs to be either ported over to other languages (for various reasons) or updated and new things written because Perl is the only language that's both abstract enough and not too processor intensive to run on the embedded systems we deal with. Therefore, you're going to start seeing a lot more Perl posts on this blog.

Setting up Tomcat (5.5) on Ubuntu Server 8.10

I recently ran into some old quirks when provisioning a new server for our company's web applications on Ubuntu 8.10 (Intrepid Ibex). Because the manager apps are no longer installed by default, you need to add extra packages to the list to install when installing Tomcat :

sudo apt-get install -y tomcat5.5 tomcat5.5-admin tomcat5.5-webapps

If you're copying configuration over from a previous Tomcat / Ubuntu installation, you need to make sure the permissions on all the files you copy are set correctly. In most cases, you'll have to run :

chown -R tomcat55:adm [file and folder list here]

If you're securing the applications with a certificate, try to make sure it's valid for your location and ensure that you've set it properly in your server.xml configuration file. If you want useful logging, you'll also have to place a log4j.properties file in

$CATALINA_HOME/common/classes

Hope this helps.

Dumping just your schema with MySQL dump

A simple one-liner :

mysqldump -u root -p mydatabasename --no-data=true --add-drop-table=false > test_dump.sql

With this command, you'll be prompted for your root password. I got this from here. Simple

The Curious Case of Damned DataIntegrityViolationException

In one of the projects on which I contract, we recently started encountering a problem importing and parsing text record files into our system which previously had no problem. My first thought on hearing this was that the partner from which we obtain the files had changed the file format (again). Upon closer inspection, nothing had changed in the files. My next step was to try importing them into a development system and seeing what was going on. As it turned out, the application was catching Spring's DataIntegrityViolationException. I was floored as soon as I saw this because our application was supposed to be catching this exception behind one of the business interfaces and converting it to an internal exception which is used in business logic. After some more poking around to confirm what was really going on, I threw the problem into google, and on the second result was a post in the Spring forum made by a user having exactly the same problem I was.


To summarize their problem quickly, they were using a transaction manager, and they were intercepting their business methods (via interfaces) with Aspects, which we're also doing. The problem was this : as soon as the internal Aspects were applied to the business interface, this changed the ordering of advice applied to the interface implementor, so now the Hibernate session underneath was getting flushed later by the transaction manager, instead of in the business method where it had been flushed previously. The result of this was that now DataIntegrityViolationExceptions were being thrown outside of the interecepted method, instead of inside where it was expected. A manual session.flush() inside of a HibernateCallback within the business method fixed this :

 /**
  * @see AchPaymentNoticeOfChangeService#registerNoc(AchPaymentNoticeOfChange)
  */
 @Override
 public void registerNoc(final AchPaymentNoticeOfChange changeNotification) throws IllegalArgumentException, NoticeOfChangeAlreadyExistsException, Exception {
  try {
   getHibernateTemplate().execute(new HibernateCallback() {
    @Override
    public Object doInHibernate(Session session) throws HibernateException, SQLException {
     
     session.save (changeNotification);
     
     // flush the session to ensure that the database gets synchronized
     // the end of this call, rather than waiting for any transaction
     // managers to handle it and risk letting a DataIntegrityViolationException
     // occur outside of this method's handling
     session.flush();
     
     return null;
    }
   });
  } catch (DataIntegrityViolationException dive) {
   throw new NoticeOfChangeAlreadyExistsException("A notice of change already exists for payment ["+changeNotification.getAchPayment().getId()+"]", dive, changeNotification);
  } catch (Exception e) {
   throw e;
  }
 }

I hope this post finds somebody else who runs into this problem.

Composing XML in C# 2.0 or later

When testing some custom XML serialization I was writing for a project, I ran across a quirk of the XmlWriter created by XmlWriter#Create() : The writer that gets produced by this method doesn't actually write out XML to whatever stream or file you've given it in the Create method until Close() is called on the generated writer. This means that if you've been using the XmlWriter along with a using() statement, you're fine, but if you haven't been using it, as I have in the unit tests I've been trying to write, you're going to get some unexpected results. Something to pay attention to.

Visual Studio (2010?) Debugging Gotchas - Part I

I recently ran across a problem where I was trying to debug some code and the Visual Studio debugger wouldn't stop in my class. It would stop in the test class from which I was debugging, but not the class I really wanted to debug. I looked on the breakpoint and noticed that it was transparent, so I hovered over it to view the tooltip, and the tooltip informed me that my class had a DebuggerStepThroughAttribute assigned to it. My first thought was "what ? that's bullshit", and then it occurred to me that I hadn't looked at the rest of the (partial) class which was defined in another file that was generated from an XML schema by xsd.exe. Sure enough, xsd.exe places DebuggerStepThroughAttribute attributes on the classes it generates. Why is this default behaviour ? This was an annoying as hell bug that took time out of my day that's better devoted to other things, like being productive so that I don't get shit from my boss. It also took more time than I'd care to admit to, largely due to my inexperience with Visual Studio and .NET. I've had yet to see anything like this coming from a Java / scripting background.

Tricky styling issues in WPF

For about the last 8 or 9 hours (spread across two days) I've been troubleshooting a styling issue in WPF. I have a list of items that I'm displaying in a ListBox that have an 'enabled' property, which is an enum with values OFF and ON. Understand that this type was generated from an XML schema which is very tightly controlled, hence why the type is not a boolean (as would make sense with a name like 'enabled'). I've been trying to create a DataTemplate for the ListBoxItems so that they'll each have an icon associated with them depending on whether they're enabled or not. My original list looked like this :

<ListBox x:Name="ProcedureList" ItemsSource="{Binding Path=procedure}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
  <ListBox.Resources>
    <Style TargetType="{x:Type ListBoxItem}">
      <EventSetter Event="MouseDoubleClick" Handler="WeldProcedure_MouseDoubleClick" />
      <Setter Property="HorizontalContentAlignment" Value="Stretch" />
    </Style>
    <Style TargetType="{x:Type Image}">
      <Style.Triggers>
        <DataTrigger Binding="{Binding}" Value="OFF">
          <Setter Property="Image.Source" Value="Resources/Error_16x16_72.png"/>
        </DataTrigger>
        <DataTrigger Binding="{Binding}" Value="ON">
          <Setter Property="Image.Source" Value="Resources/Success_16x16_72.png"/>
        </DataTrigger>
      </Style.Triggers>
    </Style>
  </ListBox.Resources>
  <ListBox.ItemTemplate>
    <DataTemplate DataType="{x:Type model:WeldingProcedure}">
      <DockPanel HorizontalAlignment="Stretch" LastChildFill="True">
        <Image DockPanel.Dock="Right" Height="16" Width="16" DataContext="{Binding Path=enabled}" ToolTip="Disabled"/>
        <TextBlock DockPanel.Dock="Left" VerticalAlignment="Center" TextAlignment="Left" Text="{Binding Path=procedureName}"/>
      </DockPanel>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

However, the images in the DataTemplate were not getting styled with the images as they should have been. As it turns out, if you're referencing default styles in Templates as above, the style resolution doesn't go outside of the template, so the default styling for all Image elements as above needs to go *inside* the DataTemplate resources :

<ListBox x:Name="ProcedureList" ItemsSource="{Binding Path=procedure}" HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
  <ListBox.Resources>
    <Style TargetType="{x:Type ListBoxItem}">
      <EventSetter Event="MouseDoubleClick" Handler="WeldProcedure_MouseDoubleClick" />
      <Setter Property="HorizontalContentAlignment" Value="Stretch" />
    </Style>
  </ListBox.Resources>
  <ListBox.ItemTemplate>
    <DataTemplate DataType="{x:Type model:WeldingProcedure}">
      <DataTemplate.Resources>
        <Style TargetType="{x:Type Image}">
          <Style.Triggers>
            <DataTrigger Binding="{Binding}" Value="OFF">
              <Setter Property="Image.Source" Value="Resources/Error_16x16_72.png"/>
            </DataTrigger>
            <DataTrigger Binding="{Binding}" Value="ON">
              <Setter Property="Image.Source" Value="Resources/Success_16x16_72.png"/>
            </DataTrigger>
          </Style.Triggers>
        </Style>
      </DataTemplate.Resources>
      <DockPanel HorizontalAlignment="Stretch" LastChildFill="True">
        <Image DockPanel.Dock="Right" Height="16" Width="16" DataContext="{Binding Path=enabled}" ToolTip="Disabled"/>
        <TextBlock DockPanel.Dock="Left" VerticalAlignment="Center" TextAlignment="Left" Text="{Binding Path=procedureName}"/>
      </DockPanel>
    </DataTemplate>
  </ListBox.ItemTemplate>
</ListBox>

Generating XML objects from a schema in .NET

In my last job, I frequently made use of the JAXB library provided with the Java SDK for object de/serialization. I chose to generate my schemata from objects back then because I started off with the business objects and I knew how I wanted to serialize them to XML. Now I have the reverse situation, and I'm using a new language. As it turns out, generating classes from XML schema is dead easy : use the xsd.exe tool. It comes with .NET.

Useful GIMP tricks - Batch file conversion

Now that I've started having to do a lot more documenting for my job, I've found myself importing a lot of pictures taken as steps in tutorials and for providing figures. Since the camera gives us a nice, high-res version that's not really suitable for documentation, I have to scale the images down so that they're in a nice, readable size. When your tutorial has 30 steps, and an image (or even two or three) is required for *each step*, this can mean a lot of manual clicking, dragging, opening and saving in an image editor. Fortunately, GIMP has a plugin called Davids Batch Processor that allows you to easily do fairly simple transforms to file and output them in the format (that's most likely) of your choice. For the simple tasks of rotating, resizing (scaling) and exporting the images in a new format, this plugin's great. There's a tutorial on the site and the plugin itself has already proven to be exceedingly useful for me. I hope it will be for you too.

Subtleties of Perl - Reading files

I've recently begun a new job, and with it has come a whole new segment of the software development universe. The new job uses a lot of Perl, C, Bash and various other languages to get stuff done. Today, I ran afoul of a Perl idiosyncrasy that's worth making a note of, because I'm sure I'll stumble across this problem again and I'm going to need to refer to this in the future. I should also note that I'm writing this as I'm waiting for a significantly large file to parse.

We have large log files that we parse on a daily basis to extract summary information from them about mechanical systems. We read the files, and then output a summary on a secondly basis, one line at a time. Recently, I ran afoul of Perl's file reading mechanisms. When reading files in Perl, there's any number of ways to do so, and it turns out that for the longest time, we've been using the wrong one. Previously, we had been using :

foreach my $line_of_log (<LOG>)
{
    // DO STUFF WITH $line_of_log
}

We thought that this was reading the file in one line of the log file at a time, processing it, and then moving on. What it was actually doing was reading (or "slurping") the whole file into memory, and giving us an array of strings, which we processed one line at a time. After 10 minutes of cursory Googling, I ran across a tutorial which presented this :

while (<LOG>)
{
    my $line_of_log = $_;
    // DO STUFF WITH $line_of_log
}

The 'while' version of the file read actually does what we thought we where doing all along: reading one line from the file, and then doing stuff with it. The difference between the two methods is that in the 'foreach' version, the entire input file gets read into memory, whereas in the 'while' version, only a single line gets read into memory at any given time. As it turns out, another difference is that reading in a 7 MB file resulted in Perl grabbing 34 MB of memory with the 'foreach' version, but only 2.2 MB with the 'while' version. That's an ENTIRE ORDER OF MAGNITUDE in difference!. This also makes a huge difference when running Perl on memory-limited systems, as we are.