Came across these while browsing the C# Code Samples page on the MSDN C# Developer Center:

Code access security with C# (CodeAccessSecuritySample.exe).
Demonstrates the use of .NET Framework Code Access Security, in which code can have permissions independent of the person executing the code.

Web Services Security with C# (WebServiceSecuritySample.exe).
Examines how to use IIS to perform user authentication so that no changes to the Web Service are required in order to provide superior security.

All the samples can be found @
http://msdn.microsoft.com/vcsharp/downloads/samples/23samples/default.aspx

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