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ComCompatibleVersionAttribute Class

Note: This namespace, class, or member is supported only in version 1.1 of the .NET Framework.

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.

For a list of all members of this type, see ComCompatibleVersionAttribute Members.


[Visual Basic]
NotInheritable Public Class ComCompatibleVersionAttribute
   Inherits Attribute
public sealed class ComCompatibleVersionAttribute : Attribute
public __gc __sealed class ComCompatibleVersionAttribute : public
class ComCompatibleVersionAttribute extends Attribute

Thread Safety

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


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 System.Runtime.InteropServices.ComCompatibleVersionAttribute.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 System.Runtime.InteropServices.ComCompatibleAttribute 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.


[Visual Basic, C#] 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.

[Visual Basic] 
Imports System
Imports System.Runtime.Interop
Assembly: AssemblyVersion ("")
Assembly: ComCompatibleVersionAttribute(1,0,0,0)
Module MyNamespace
  Public Class MyClass
    ' Insert code.
  End Class
using System;
using System.Runtime.InteropServices;
[Assembly: AssemblyVersion ("")
[Assembly: ComCompatibleVersion(1,0,0,0)]
namespace MyNamespace
  class MyClass
    // Insert code.

[C++, JScript] No example is available for C++ or JScript. To view a Visual Basic or C# example, click the Language Filter button Language Filter in the upper-left corner of the page.


Namespace: System.Runtime.InteropServices

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

Assembly: Mscorlib (in Mscorlib.dll)

See Also

ComCompatibleVersionAttribute Members | System.Runtime.InteropServices Namespace | GuidAttribute | Type Library Exporter (Tlbexp.exe)