When you specify the /tlb option, Regasm.exe generates and registers a type library describing the types found in the assembly. Regasm.exe places the generated type libraries in the current working directory or the directory specified for the output file. Generating a type library for an assembly that references other assemblies may cause several type libraries to be generated at once. You can use the type library to provide type information to development tools like Visual Studio 2005. You should not use the /tlb option if the assembly you are registering was produced by the Type Library Importer (Tlbimp.exe [ http://msdn2.microsoft.com/en-us/library/tt0cf3sx(VS.80).aspx ] ). You cannot export a type library from an assembly that was imported from a type library. Using the /tlb option has the same effect as using the Type Library Exporter (Tlbexp.exe [ http://msdn2.microsoft.com/en-us/library/hfzzah2c(VS.80).aspx ] ) and Regasm.exe, with the exception that Tlbexp.exe does not register the type library it produces. If you use the /tlb option to registered a type library, you can use /tlb option with the /unregister option to unregistered the type library. Using the two options together will unregister the type library and interface entries, which can clean the registry considerably.

When you register an assembly for use by COM, Regasm.exe adds entries to the registry on the local computer. More specifically, it creates version-dependent registry keys that allow multiple versions of the same assembly to run side by side on a computer. The first time an assembly is registered, one top-level key is created for the assembly and a unique subkey is created for the specific version. Each time you register a new version of the assembly, Regasm.exe creates a subkey for the new version.

For example, consider a scenario where you register the managed component, myComp.dll, version 1.0.0.0 for use by COM. Later, you register myComp.dll, version 2.0.0.0. You determine that all COM client applications on the computer are using myComp.dll version 2.0.0.0 and you decide to unregister myComponent.dll version 1.0.0.0. This registry scheme allows you to unregister myComp.dll version 1.0.0.0 because only the version 1.0.0.0 subkey is removed.

After registering an assembly using Regasm.exe, you can install it in the global assembly cache [ http://msdn2.microsoft.com/en-us/library/yf1d93sz(VS.80).aspx ] so that it can be activated from any COM client. If the assembly is only going to be activated by a single application, you can place it in that application's directory.

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regasm myTest.dll

The following command generates the file myTest.reg, which contains all the necessary registry entries. This command does not update the registry.

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regasm myTest.dll /regfile:myTest.reg

The following command registers all public classes contained in myTest.dll, and generates and registers the type library myTest.tlb, which contains definitions of all the public types defined in myTest.dll.

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regasm myTest.dll /tlb:myTest.tlb

Concepts