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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)

'Declaration
<AttributeUsageAttribute(AttributeTargets.Assembly, Inherited:=False)> _
<ComVisibleAttribute(True)> _
Public NotInheritable Class ComCompatibleVersionAttribute
	Inherits Attribute
'Usage
Dim instance As ComCompatibleVersionAttribute

/** @attribute AttributeUsageAttribute(AttributeTargets.Assembly, Inherited=false) */ 
/** @attribute ComVisibleAttribute(true) */ 
public final class ComCompatibleVersionAttribute extends Attribute
AttributeUsageAttribute(AttributeTargets.Assembly, Inherited=false) 
ComVisibleAttribute(true) 
public final class ComCompatibleVersionAttribute extends Attribute
Not applicable.

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 1.0.0.0 in an assembly with a higher version number. Regardless of the new assembly version, all CLSIDs in the assembly are generated using version 1.0.0.0 instead of using the current assembly version.

Imports System
 Imports System.Runtime.Interop
 Assembly: AssemblyVersion ("3.0.0.0")
 Assembly: ComCompatibleVersionAttribute(1,0,0,0)
 Module MyNamespace
   Public Class MyClass
     ' Insert code.
   End Class

System.Object
   System.Attribute
    System.Runtime.InteropServices.ComCompatibleVersionAttribute

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 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1

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