The .NET 4 source does not work with the current .NET 4 Framework library.
For source see
For installation instructions see
Configuring Microsoft Visual Studio for local debugging of Reference Source
The .NET 4 source fails with a No Source Available error since the source is out of date.
The .NET 4 version for this source is 4.0.30319.1.
Recent Microsoft updates changed some DLLs to 4.0.30319.233.
The 4.0.30319.1 source does not debug with the current 4.0.30319.233 DLLs.
We urgently need Microsoft to update the .NET Framework 4 Reference source to the current update 4.0.30319.233.
Moreover, the sources should be updated along with .NET 4 updates on a continuing basis.