[.net] What is the GAC in .NET?

Just looking for a short overview of GAC for a layman, not a link please.

This question is related to .net gac

The answer is


Centralized DLL library.


The Global Assembly Cache (GAC) is a folder in Windows directory to store the .NET assemblies that are specifically designated to be shared by all applications executed on a system. Assemblies can be shared among multiple applications on the machine by registering them in global Assembly cache(GAC). GAC is a machine wide a local cache of assemblies maintained by the .NET Framework.


GAC = Global Assembly Cache

Let's break it down:

  • global - applies to the entire machine
  • assembly - what .NET calls its code-libraries (DLLs)
  • cache - a place to store things for faster/common access

So the GAC must be a place to store code libraries so they're accessible to all applications running on the machine.


Exe Application, first of all, references from a current directory to a subdirectory. And then, system directory. VS6.0 system directory was ..windows/system32. .NET system directory is like the below GAC path.

  1. GAC path

    1) C:\Windows\Assembly (for .NET 2.0 ~ 3.5)

    2) C:\Windows\Microsoft.NET\assembly (for .NET 4.0)

  2. How to install an assembly into GAC (as Administrator)

    1) Drag and Drop

    2) Use GacUtil.exe with Visual Studio Command Prompt

     gacutil -i [Path][Assembly Name].dll
    
    • Note: To install an assembly into the GAC, the assembly must be strongly named. Otherwise you get an error like this: Failure adding assembly to the cache: Attempt to install an assembly without a strong name.
  3. How to uninstall an assembly from GAC (as Administrator)

     gacutil -u [Assembly Name], Version=1.0.0.0, PublickeyToken=7896a3567gh
    
    • Note: has no extention, .dll. Version and PublickeyToken can be omitted and be checked in GAC assembly.

GAC (Global Assembly Cache) is where all shared .NET assembly reside.


Global Assembly Cache

Each computer where the common language runtime is installed has a machine-wide code cache called the global assembly cache. The global assembly cache stores assemblies specifically designated to be shared by several applications on the computer.

You should share assemblies by installing them into the global assembly cache only when you need to. As a general guideline, keep assembly dependencies private, and locate assemblies in the application directory unless sharing an assembly is explicitly required. In addition, it is not necessary to install assemblies into the global assembly cache to make them accessible to COM interop or unmanaged code.

The things MSDN contains may surprise you... you can usually read it like an article. The straightforward and most important bits at the top, the intricate details deeper down. It certainly explains it better than I could.

Note that Visual Studio displays all the DLLs in the GAC in the .NET tab of the References window. (Right-click on a project in Solution Explorer and select Add Reference.) This should give you a more tangeable idea.


It's like the COM registry done right, with respect to the physical files as well as their interface and location information. In COM, files were everywhere, with centralised metadata. The GAC centralises the bang shoot.