Using the Windows Installer to Install Applications and Components for Side-by-Side Execution 

The Windows Installer reads the assembly table, which is maintained by the common language runtime, when installing new assemblies. The table lists all installed assemblies, including those in the global assembly cache. When installing assemblies in the global assembly cache, the Windows Installer checks this table to determine whether an assembly to be installed has the same fully qualified assembly name as an assembly that already exists in the global assembly cache. If it does not, the Windows Installer installs the assembly.

For .NET Framework version 1.1, the assembly table also contains information on the file version. This attribute describes the Win32 file version of the assembly. If you enter file version information in the Windows Installer tables for new assemblies to be installed, the Installer can compare file version information in the installer table to that stored in the assembly table in addition to comparing the fully qualified assembly names. If the fully qualified assembly name is the same as an existing assembly in the global assembly cache, and if the file version of the assembly to be installed is higher than the file version of the assembly in the global assembly cache, the Windows Installer installs the new assembly into the global assembly cache. If no file version information is provided in the Windows Installer table, only the fully qualified assembly name is used for comparison.

See Also

Concepts

Deploying Multiple Versions of an Application or Component
Guidelines for Creating Applications and Components for Side-by-Side Execution

Other Resources

Deploying Applications
Creating Multiple Versions of an Application or Component