I hate using underscores for representing members of a type. It's idiotic. If you need a prefix to distinguish your local variables from your members with the same name, there's a built-in way of doing it: the 'this' keyword.
"But ... that's more typing ... it takes longer" = > NO! IT FUCKING DOESN'T
1) Between Intellisense in your tools and automatic code formatters, it can actually take less when you apply the formatter regularly and share the settings with your team.
2) The underscore is harder to type, especially on a QWERTY keyboard (I use Dvorak)
If you use ReSharper, the Code Cleanup feature can fix this up for you in short order. As part of your cleanup profile, ensure that you select "Arrange qualifiers" in the settings.