How do I include System.Xml version 2.0 in a .NET 4.5 website project?

Hello,

My older website project (upgraded to .NET 4.5) is giving this error:

Error  Reference.svcmap: Could not load file or assembly 'System.Xml, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e' or one of its dependencies. The system cannot find the file specified.  App_WebReferences/VideoService/  

How do I include this assembly?

The website project already has System.Xml 4.0 included when I attempt to include the reference.  (The assembly is not shown in the bin folder.)

I have already included an assembly binding in the web.config file, but am still getting the error.

<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="System.Xml"  culture="neutral" publicKeyToken="7cec85d7bea7798e"/><codeBase version="2.0.5.0" href="FILE://C:/Windows/Microsoft.NET/Framework/2.0.50727/System.Xml.dll"/></dependentAssembly></assemblyBinding>

Any suggestions?

Thanks.