System.Data and many other files missing from Windows\Microsoft.NET Folder, not restored by repair tool or turning features off and on

[jimhabegger]

Not an issue with .NET itself, but I'm hoping that someone here can help me.

When I tried to start PowerShell or Duplicate Cleaner, I got this message.

Could not load file or assembly ‘System.Data, Version =4.0.0.0. Culture=neutral, PublicKeyToken=b77a5c561934e089’ or one of its dependencies. The system cannot find the file specified.

I discovered that these two folders were empty:

C:\Windows\Microsoft.NET\assembly\GAC_32\System.Data\v4.0_4.0.0.0__b77a5c561934e089
C:\Windows\Microsoft.NET\assembly\GAC_64\System.Data\v4.0_4.0.0.0__b77a5c561934e089

I was able to fix the immediate problem by copying System.Data from another computer, but in the process I discovered that many other files are missing from my Microsoft.NET Folder.

Before copying System.Data from another computer, I tried the repair tool, and turning the NET Framework features off and on, but neither of those restored System.Data, and there are still many files missing from my Microsoft.NET Folder.

[jimhabegger]

After a few hours of searching and only finding two examples of files missing from the Microsoft.NET folder on the user side, and not finding any examples where the files were restored without a clean install of Windows, I'm thinking that in most cases that would be the only solution, if the files aren't restored by DISM and sfc.