The assembly version number is part of an assembly's identity and plays a key part in binding to the assembly and in version policy. The default version policy for the runtime is that applications run only with the versions they were built and tested with, unless overridden by explicit version policy in configuration files (the application configuration file, the publisher policy file, and the computer's administrator configuration file). See [<topic://cpconassembliesoverview>] for more information.

The version number has four parts, as follows:

<major version>.<minor version>.<build number>.<revision>

You can specify all the values or you can accept the default build number, revision number, or both by using an asterisk (*). For example, [assembly:AssemblyVersion("2.3.25.1")] indicates 2 as the major version, 3 as the minor version, 25 as the build number, and 1 as the revision number. A version number such as [assembly:AssemblyVersion("1.2.*")] specifies 1 as the major version, 2 as the minor version, and accepts the default build and revision numbers. A version number such as [assembly:AssemblyVersion("1.2.15.*")] specifies 1 as the major version, 2 as the minor version, 15 as the build number, and accepts the default revision number. The default build number increments daily. The default revision number is random.

The assembly major and minor versions are used as the type library version number when the assembly is exported. Some COM hosts do not accept type libraries with the version number 0.0. Therefore, if you want to expose an assembly to COM clients, set the assembly version explicitly to 1.0 in the AssemblyVersionAttribute page for projects created outside vsprvslong and with no AssemblyVersionAttribute specified. Do this even when the assembly version is 0.0. All projects created in vsprvslong have a default assembly version of 1.0.*.

To get the name of an assembly you have loaded, call Assembly.GetName on the assembly to get an System.Reflection.AssemblyName, and then get the AssemblyName.Version property. To get the name of an assembly you have not loaded, call AssemblyName.GetAssemblyName(string) from your client application to check the assembly version that your application uses.