Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling - wcf

Question

I get this below error when i add Enterprise library 5.0 file MS.Practices.EnterpriseLibrary.ExceptionHandling.dll for my wcf application.
An error occurred creating the configuration section handler for exceptionHandling: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference.
<exceptionHandling>
<exceptionPolicies>
<add name="Global Policy">
<exceptionTypes>
<add name="Exception" type="System.Exception, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" postHandlingAction="None">
<exceptionHandlers>
<add name="Wrap Handler" type="Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.WrapHandler, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling" exceptionMessage="Global Message." wrapExceptionType="ExceptionHandlingQuickStart.BusinessLayer.BusinessLayerException, ExceptionHandlingQuickStart.BusinessLayer" />
<add name="Custom Handler" type="AppMessageExceptionHandler, ExceptionLibraryForWCF"/>
</exceptionHandlers>
</add>
</exceptionTypes>
</add>
<add name="Handle and Resume Policy">
<exceptionTypes>
<add name="Exception" type="System.Exception, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" postHandlingAction="None">
<exceptionHandlers/>
</add>
</exceptionTypes>
</add>
<add name="Propagate Policy">
<exceptionTypes>
<add name="Exception" type="System.Exception, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" postHandlingAction="NotifyRethrow">
<exceptionHandlers/>
</add>
</exceptionTypes>
</add>
<add name="Replace Policy">
<exceptionTypes>
<add name="SecurityException" type="System.Security.SecurityException, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" postHandlingAction="ThrowNewException">
<exceptionHandlers>
<add name="Replace Handler" type="Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.ReplaceHandler, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" exceptionMessage="Replaced Exception: User is not authorized to peform the requested action." replaceExceptionType="System.ApplicationException, mscorlib"/>
</exceptionHandlers>
</add>
</exceptionTypes>
</add>
<add name="Wrap Policy">
<exceptionTypes>
<add name="DBConcurrencyException" type="System.Data.DBConcurrencyException, System.Data, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" postHandlingAction="ThrowNewException">
<exceptionHandlers>
<!--<add name="Wrap Handler" type="Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.WrapHandler, Microsoft.Practices.EnterpriseLibrary.ExceptionHandling" exceptionMessage="Wrapped Exception: A recoverable error occurred while attempting to access the database." wrapExceptionType="ExceptionHandlingQuickStart.BusinessLayer.BusinessLayerException, ExceptionHandlingQuickStart.BusinessLayer" /> -->
</exceptionHandlers>
</add>
</exceptionTypes>
</add>
</exceptionPolicies>
Below is my web.config declaration for my exception handling
-->

Answer 1

Your web.config isn't actually in the post.
In any event, you've got a reference to Entlib 2.0 in your config file. You need to update to point at the Entlib 5 version number and public key token. It's probably in your element, but if it's there I wouldn't be surprised if the rest of your file also had the wrong version #'s.
[update on further reflection]
Actually, based on the error message, there's another possibility - the runtime is finding the 2.0 assembly instead of the 5.0 assembly when it goes to load. Double check all your assembly references, and check your bin directory - make sure it's got the right assembly in it.
You can also try running the fuslogvw tool on the web server - it'll tell you what assemblies the runtime tried to load, and where it looked for them.

Answer 2

I had a similar problem caused by source control. I checked in an old copy of a project file after a coworker updated a project. I simply found the project that was referencing the assembly/ project reference in error, removed the reference, re-added the reference and rebuilt the solution. bingo.