ASP.NET - Method 'get_EnableCdn' in type 'System.Web.UI.ScriptManager' from assembly 'System.Web.Extensions' does not have an implementation

Issue:
Error: "Method 'get_EnableCdn' in type 'System.Web.UI.ScriptManager' from assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' does not have an implementation."

Reason:
This error is frequent in ASP.NET projects which are migrated from an older version of .NET Framework to a new version of Framework. So mostly in projected build in Visual Studio 2005/2008 when build in Visual Studio 2010, this error might occur. This is because of the web application referring to an older version of "System.Web.Extensions" Assembly.

Solution:
You will have to explicitly reference to the latest version of the "System.Web.Extensions" Assembly. You can do it in web.config of your website/web application as below.

  <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
    <dependentAssembly>
      <assemblyIdentity name="System.Web.Extensions" publicKeyToken="31bf3856ad364e35"/>
      <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/>
    </dependentAssembly>
    <dependentAssembly>
      <assemblyIdentity name="System.Web.Extensions.Design" publicKeyToken="31bf3856ad364e35"/>
      <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="3.5.0.0"/>
    </dependentAssembly>
  </assemblyBinding>