Get Remotesoft .NET explorer,
hxxp://www.remotesoft.com/eval_download/Remotesoft_DOTNET_Explorer_Evaluation.msi
or .NET SDK from M$ and its ILDASM = .NET disassembler, and learn basics of MSIL (MS intermediate language) - maybe from here :
hxxp://msdn.microsoft.com/msdnmag/issues/01/05/bugslayer/default.aspx

Some tut is also here :
hxxp://29a.host.sk/29a-6/29a-6.203

bye