If you mean Selenium testing framework (
http://en.wikipedia.org/wiki/Selenium_%28software%29[
^]), this is the .NET Toolkit:
http://seleniumtoolkit.codeplex.com/[
^].
Please see its documentation. I don't know, maybe this is insufficient. As you say, you can find enough Java documentation, right. So, there is a hint for your: it is very usual that some software originated in Java (Selenium is the case) is later ported or wrapped for .NET and is not documented in .NET languages as well. This is quite explainable, and not a problem at all. At the level of documentation, Java is very similar to C#, even though conceptually it's very different. From the standpoint of using the documentation, this is just fine. The names of the APIs are the same, the syntax is very similar, and you always have C# API, even from reflection.
—SA