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ComCompatibleVersionAttribute Class

Indicates to a COM client that all classes in the current version of an assembly are compatible with classes in an earlier version of the assembly.

Namespace:  System.Runtime.InteropServices
Assembly:  mscorlib (in mscorlib.dll)

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

You can apply this attribute to assemblies.

By default, the Type Library Exporter (Tlbexp.exe) uses an assembly's version number to calculate class identifiers (CLSIDs). All public, COM-visible classes receive new CLSIDs each time you export a new assembly version.

You can apply the ComCompatibleVersionAttribute attribute to force all CLSIDs for classes in the current version of an assembly to be the same as CLSIDs for classes in an earlier version of the assembly. As long as the CLSIDs remain the same, a legacy COM application can use the later version of a compatible assembly after you uninstall the original assembly. If you apply the System.Runtime.InteropServices.GuidAttribute to a class to explicitly set its CLSID, the ComCompatibleVersionAttribute has no effect.

The properties of this attribute combine to form the four parts of an assembly version. Always specify the lowest version that the current assembly is backward compatible with so that version is used to calculate all CLSIDs in the assembly.

The following example shows how to specify assembly version in an assembly with a higher version number. Regardless of the new assembly version, all CLSIDs in the assembly are generated using version instead of using the current assembly version.

using System;
 using System.Runtime.InteropServices;
 [assembly: AssemblyVersion ("")
 [assembly: ComCompatibleVersion(1,0,0,0)]
 namespace MyNamespace
   class MyClass
     // Insert code.


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

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