Solving "System.Net.WebException: The remote server returned an error: (417) Expectation Failed" with a WCF service

I recently started getting the following error message when trying to connect to a web service we had put on an Azure VM running behind an Azure load balancer:

System.ServiceModel.ProtocolException: The remote server returned an unexpected response: (417) Expectation Failed. ---> System.Net.WebException: The remote server returned an error: (417) Expectation Failed.

It turns out the fix was to put the following element in my <configuration> :

<system.net>
<settings>
<!-- This is required when running in Azure VMs behind an Azure load balancer -->
<servicePointManager expect100Continue="true" />
</settings>
</system.net>