Shfusion.dll (Assembly Cache Viewer)
Beginning with the .NET Framework version 4, the Assembly Cache Viewer (Shfusion.dll) is obsolete and has been removed. Use Gacutil.exe (Global Assembly Cache Tool) to view and manipulate the global assembly cache.
There might be older versions of Shfusion.dll on your computer. When you view the global assembly cache in Windows Explorer, these older versions of the shell extension will continue to be invoked. Do not use them. They do not display .NET Framework 4 assemblies or assemblies built using the .NET Framework 4.
Gacutil.exe (Global Assembly Cache Tool)
Visual Studio and Windows SDK Command Prompts