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This chapter is from the book

This chapter is from the book

3.12. Installing a Component in the Global Assembly Cache (GAC)

You want to access your custom control from any application on a server by registering its assembly in the Global Assembly Cache, or GAC.


The Global Assembly Cache in the .NET Framework provides a central place for registering assemblies. Registered assemblies are then available to all applications, including the development environments like Visual Studio.NET and Web Matrix. The process of adding an assembly to the Global Assembly Cache can be compared to the process of registering COM components in the server, as is done in the case of Windows DNA applications.

The first step involved in adding an assembly is to strong-name the assembly. A strong name is basically assigned to an assembly or a component to distinguish it from other assemblies and components existing in the GAC. A strong name consists of an assembly identity (name, version, and so on), a public key, and a digital signature.

Assigning a strong name to an assembly ensures that it is unique, has version protection, and has code integrity. Assigning a strong name to an assembly is not a difficult task. You can use the sn.exe utility to generate strong names, which are then added to the code of the assembly. For example, to create a strong name for an assembly named sample.dll, you would write the following in the command prompt:

  c:\MyAssembly>sn -k sample.snk 

This would generate a strong name keypair and store it in a file named sample.snk. The file extension can be anything, but.SNK is normally used as a convention. The -k option creates a strong name keypair. There are other options that you can search for in MSDN.

The second step is to associate the generated strong name file with the assembly. Add the following code to your assembly to associate the strong name. By default, Visual Studio .NET projects include skeleton declarations of these attributes in the AssemblyInfo file.

  Imports System.Reflection

  <assembly: AssemblyKeyFile("sample.snk")>

Note here that the information regarding the file containing the strong name keypair is placed in the code file before any namespace declaration. Also, you must import the System.Reflection namespace in order for the statement to work, otherwise the compiler will not recognize the <assembly: AssemblyKeyFile("sample.snk")> statement.

After compiling the assembly with the statements containing the strong name information being added to it, you now have to place the assembly into the GAC. You can do this manually by simply copying and pasting the assembly into the GAC, which is located at C:\WINNT\ASSEMBLY\.

You can also use the gacutil.exe utility, installed with the .NET Framework. In order to add an assembly, you write the following on the command prompt:

  gacutil /i sample.dll

The /i option is for installation. In order to remove an assembly from the GAC, you can use the same utility, as follows:

  gacutil /u sample.dll

The /u option is for uninstalling or removing an assembly from the cache. Typing gacutil /? lists all of its options.

See Also

Section 3.1, "Declaring a Simple Custom Control"

Section 3.2, "Creating a Composite Control"

Command-Line Compilation—http://aspalliance.com/hrmalik/articles/2002/ 200211/20021101.aspx, Haroon Rasheed Malik

The .NET Assemblies—http://aspalliance.com/hrmalik/articles/2002/200202/ 20020201.aspx, Haroon Rasheed Malik

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