What gacutil.exe should I use?

Question

So, on a Win 2008 R2 Std x64, I have 6 (six) gacutil.exe all different (not counting ones in VS folders), in:

1. c:\\Program Files\\Microsoft SDKs\\Windows\\v

Answer 1

Gacutil.exe is a Windows SDK tool, not a .NET framework tool. You got two versions of the SDK on your machine. You got 6.0A from the VS2008 install, 7.0A from the VS2010 install. You also have a 64-bit operating system so you got the 64-bit tools as well. Which doesn't matter for gacutil.exe, not sure why they include it separately. Probably to keep the Visual Studio Command Prompt working, note that you have separate 32-bit and 64-bit versions of it. Which matters a lot for C++ projects. VS2010 allows targeting both CLR version 4 and CLR version 2 so that's 6 versions total.

What does matter a great deal is that you have two GACs on your machine. The GAC for .NET 4 assemblies is stored in c:\windows\microsoft.net\assembly. For earlier versions it is stored in c:\windows\assembly. You must use the proper version of gacutil.exe to get an assembly into the proper GAC. For an assembly that targets .NET 4, you must use the one in Bin\NETFX 4.0 Tools. And for earlier ones, you must use the one in Bin.

Using it not at all is best, assemblies should have the Copy Local property set on a dev machine. The GAC is a deployment detail, you'll get in trouble when your GAC has an assembly that your user's GAC doesn't have.