GAC Referencing
When you are developing a class library, you may want Visual Studio .NET to list your library in the Add Reference dialog box on the .NET tab without the user having to browse for it.
This issue is not resolved if you install your assembly to the Global Assembly Cache (GAC), because the Add Reference dialog box is path-based and does not enumerate the components from the GAC.
To display your assembly in the Add Reference dialog box, you can add a registry key, such as the following, which points to the location of the assembly
[HKEY_CURRENT_USER\SOFTWARE\Microsoft
\ .NETFramework\AssemblyFolders
\MyAssemblies]@=”C:\MyAssemblies”
–where MyAssemblies is the name of the folder in which the assemblies reside.
NOTE: You can create the this registry entry under the HKEY_LOCAL_MACHINE hive. This will change the setting for all of the users on the system. If you create this registry entry under HKEY_CURRENT_USER, this entry will affect the setting for only the current user.
Restart Visual Studio .NET after you have added the key.
MORE INFO:
Microsoft recommends that you not install your assemblies to the GAC, unless you want to share your assemblies with other applications running on that system.
Also, note that it is not possible to directly reference an assembly from the GAC in your project. If you want to use an assembly from the GAC, you should drop your assemblies to a local folder, and then add a reference to the assembly from this folder. You may want to set the Copy Local property to False for that assembly if you do not want the assembly to be copied locally to your project folders. At runtime, the application will use the assemblies from the GAC.