Sometimes we may need to find assembly files (.dll) in the Microsoft windows GAC (Global Assembly Cache), while working in the world of Microsoft.NET. The default GAC folder is located at C:\Windows\assembly, but looking in this directory , we would only find the installed versions of these assemblies.
To find the actual .dll file of these installed assemblies, just
Open Dos-Prompt & type dir fullname of the assembly followed by ‘/s‘. For example
C:\>dir Microsoft.SharePoint.IdentityModel.dll /s
Once you find the dll file, copy it to your project & enjoy coding…