Here's another problem I had when trying to get the Microsoft Enterprise Library - exception logging working.
The following error was caused because I did not add references to all the assemblies used.
MyApp.UnitTests.BuildHelperTests.DBConnectionString_Get : Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.ExceptionHandlingException : The type 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.LoggingExceptionHandler, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' cannot be resolved. Please verify the spelling is correct or that the full type name is provided.
----> System.ArgumentException : The type 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.LoggingExceptionHandler, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' cannot be resolved. Please verify the spelling is correct or that the full type name is provided.
In this case I needed to add reference to Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.dll.
Also, when unit testing my app, VS did not copy this (and a couple of other assemblies) from the original code project to the unit test project - so the solution here was to add a post build event to copy them across to the unit test target (bin/debug) dir.
HTH
Tim