Here I will explain 2 ways to deploy DLL in GAC(add dll to gac). Before you are going to install your DLL, You should make sure that your assembly is having a strong name.The first method to achieve this task is with the help of .NET Framework SDK V2.0/V4.0 , and the second method is with the help of ‘GACUTIL’. Now let us see How to install DLL in GAC ? How to Add dll to gac ?.And also in framework 4.0 you can directly replace the dll in Assembly .
Using Microsoft .NET Framework SDK v2.0/V.4.0:
[Make sure that you installed .NET Framework SDK v2.0/V.40 in your mechine. If not Please download from the below given url and install it]
1. Click Start > All Programs > Administrative Tools > Microsoft .NET Framework 2.0/4.0 Configuration.
2. Click Manage the Assembly Cache.
3. Select Add an Assembly to the Assembly Cache.
4. Browse and select your DLL , which you want to install it in GAC
5. Click Open. This will deploy the selected assemblies into the Global Assembly Cache (GAC).
6. Restart the IIS.
for more details visit: http://dotnetstock.com/technical/how-to-install-dll-in-gac/
let me know if this helps..