Install Both of the below links
Note: (For Vista and Windows Server 2008 >>> Windows6.0 and For Windows 7 and Windows Server 2008 R2, >>> Windows6.1. )
Windows Identity Foundation SDK
Note: Download the 3.5 version for Visual Studio 2008 and .NET 3.5, the 4.0 version for Visual Studio 2010 and .NET 4.0.
Then Only, You will able to get the assembly called Microsoft.IdentityModel