Scott Hanselman's ComputerZen.com

Take note of the Debugger.IsAttached property to find out whether the code is running in debugger or not.

                  if( System.Diagnostics.Debugger.IsAttached )
                  {
                        // Do special things (give more info to the development user)
                        Console.WriteLine("Yes, running in debugger");                  
                  }
                  else
                  {
                        Console.WriteLine("Not running in debugger");
                  }

System.Data.dll uses the above feature to debug Stored procedures.  Opens a memory mapped file for enabling debugging of sprocs. It issues sp_sdidebug which is used to turn on or off TSQL debugging.

Disclaimer:
The code above shows only the features of .NET and in no way suggest/dictates/advices the usage of this particular feature.