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.

public ref class ComCompatibleVersionAttribute sealed : Attribute
[System.AttributeUsage(System.AttributeTargets.Assembly, Inherited=false)]
public sealed class ComCompatibleVersionAttribute : Attribute
type ComCompatibleVersionAttribute = class
    inherit Attribute
Public NotInheritable Class ComCompatibleVersionAttribute
Inherits Attribute


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 namespace System;
using namespace System::Reflection;
using namespace System::Runtime::InteropServices;

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

[assembly: AssemblyVersion("")]
[assembly: ComCompatibleVersion(1,0,0,0)]
namespace MyNamespace
    public class TheClass
        // Insert code.
Imports System.Reflection
Imports System.Runtime.InteropServices

<assembly: AssemblyVersion("")>
<assembly: ComCompatibleVersion(1,0,0,0)>
Namespace MyNamespace
    Public Class TheClass
        ' Insert code.
    End Class
End Namespace


You can apply this attribute to assemblies.

By default, the Tlbexp.exe (Type Library Exporter) 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.


ComCompatibleVersionAttribute(Int32, Int32, Int32, Int32)

Initializes a new instance of the ComCompatibleVersionAttribute class with the major version, minor version, build, and revision numbers of the assembly.



Gets the build number of the assembly.


Gets the major version number of the assembly.


Gets the minor version number of the assembly.


Gets the revision number of the assembly.


When implemented in a derived class, gets a unique identifier for this Attribute.

(Inherited from Attribute)



Returns a value that indicates whether this instance is equal to a specified object.

(Inherited from Attribute)

Returns the hash code for this instance.

(Inherited from Attribute)

Gets the Type of the current instance.

(Inherited from Object)

When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

(Inherited from Attribute)

When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.

(Inherited from Attribute)

Creates a shallow copy of the current Object.

(Inherited from Object)

Returns a string that represents the current object.

(Inherited from Object)

Explicit Interface Implementations

_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.

(Inherited from Attribute)
_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.

(Inherited from Attribute)

Retrieves the number of type information interfaces that an object provides (either 0 or 1).

(Inherited from Attribute)
_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.

(Inherited from Attribute)

Applies to

See also