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AssemblyVersionAttribute Class

Specifies the version of the assembly being attributed.

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[AttributeUsageAttribute(AttributeTargets.Assembly, Inherited = false)]
public sealed class AssemblyVersionAttribute : Attribute

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 Assemblies Overview for more information.


Version checking only occurs with strong-named assemblies.

The version number has four parts, as follows:

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

Important noteImportant Note:

All components of the version must be integers greater than or equal to 0. Metadata restricts the major, minor, build, and revision components for an assembly to a maximum value of UInt16.MaxValue - 1. If a component exceeds this value, a compilation error occurs.

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("")] 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.


If you specify an asterisk for the build number, you cannot specify a revision number.

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 Visual Studio 2005 and with no AssemblyVersionAttribute specified. Do this even when the assembly version is 0.0. All projects created in Visual Studio 2005 have a default assembly version of 1.0.*.

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


Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0