In this post I am going to show you how we can configure the post build event to deploy an Assembly to GAC.

The Global Assembly Cache (GAC) is a Cache for globally available Assemblies. Most of the shared assemblies are installed inside GAC to shared across different applications.


The Global Assembly Cache tool (Gacutil.exe) allow us to manipulate the contents of the global assembly cache along with install and un-install Assembly. During the development, we generally take help of gacutil from command prompt to install or uninstall assemblies into or from GAC. This is a repetitive process, every time you made some changes in your library you might need to deploy it into the GAC.

Visual Studio has a nice feature called Pre-Build and Post-Build events. Using these events we execute some specific commands before or after the build.


Installing Assembly to the GAC requires admin privileges. Visual Studio must be started with elevated rights. From the Project Properties Window Page of the class library ( which you want to put into GAC) , Navigate to “Build Events” Tab. Build Events tab having two command line option for both Pre-Build and Post-Build event. We will be configuring the Post Build Event to install the dll into GAC because we want to put the dll into GAC after the successful build.

Below is the typical syntax for installing Assembly into GAC from command prompt which we used generally

gacutil [options] [assemblyName | assemblyPath | assemblyListFile]

Visual Studio Build Events also use the same syntax. But, the interesting part is the Location of GAC. Yes, the GAC was split into two. We all knows, .NET 4.0 introduced CLR 4.0. NET Framework 2.0 and .NET Framework 3.5 targeted to CLR 2.0 and .NET Framework 4.0 is targeted to CLR 4.0. The GAC is now split into private GAC’s for each runtime that targeted differently to CLR 2.0 and CLR 4.0 . I will recommend you read the article “Understanding the CLR Binding” for more details.

Let’s assume, the Assembly is targeted to .NET 4.5 . To Add this Assembly, we have to specify the below Post-Build Command.

“%ProgramFiles%\Microsoft SDKs\Windows\v8.1A\bin\NETFX 4.5.1 Tools\gacutil.exe” /i “$(TargetPath)”

$(TargetPath) is a pre defined macros that returns the DLL’s full path.

Make sure that key is added, you can create a strong name using Strong Name tool . Open Visual Studio Command Prompt and type the below command.

sn –k > c:\mytestkey.snk

This will generates and writes the public and private key pair in C:\mytestkey.snk file. 

Once you have done with the snk file generation, go back to visual studio > Properties Pages > Signing Tab. Enabled the “Sing the assembly” option. This will allow you to choose the “snk” file.

From the “Choose a strong name key file” dropdown, browse the newly generated snk (mytestkey.snk) file.

That all, now you can build the application and check the “Output window” as well for details.

For .NET Framework 3.5, if you have use below command as post build event

C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\bin\gacutil.exe” /i “$(TargetPath)”

So you really don’t not need to run gacutil command from command prompt ever time after successful build. Visual Studio will take care of each and every thing automatically.

For this type of scenarios, Output window is very important, because you can get details of the execution from here only. Similarly like Post-Build event, you can use Pre-Build event to remove some assemblies from GAC.