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ClassInterfaceType Enumeration

Identifies the type of class interface that is generated for a class.

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

public enum ClassInterfaceType

Member nameDescription
Supported by the .NET Compact FrameworkNoneIndicates that no class interface is generated for the class. If no interfaces are implemented explicitly, the class can only provide late-bound access through the IDispatch interface. This is the recommended setting for ClassInterfaceAttribute. Using ClassInterfaceType.None is the only way to expose functionality through interfaces implemented explicitly by the class.

Type Library Exporter (Tlbexp.exe) exposes the first public, COM-visible interface implemented by the class as the default interface of the coclass. Beginning with the .NET Framework version 2.0, you can specify the default interface exposed to COM by using the ComDefaultInterfaceAttribute attribute. If the class implements no interfaces, the first public, COM-visible interface implemented by a base class becomes the default interface (starting with the most recently derived base class and working backward). Tlbexp.exe exposes _Object as the default interface if neither the class nor its base classes implement interfaces.

AutoDispatchIndicates that the class only supports late binding for COM clients. A dispinterface for the class is automatically exposed to COM clients on request. The type library produced by Type Library Exporter (Tlbexp.exe) does not contain type information for the dispinterface in order to prevent clients from caching the DISPIDs of the interface. The dispinterface does not exhibit the versioning problems described in ClassInterfaceAttribute because clients can only late-bind to the interface.

This is the default setting for ClassInterfaceAttribute.

AutoDualIndicates that a dual class interface is automatically generated for the class and exposed to COM. Type information is produced for the class interface and published in the type library. Using AutoDual is strongly discouraged because of the versioning limitations described in ClassInterfaceAttribute.

This enumeration is used in conjunction with the ClassInterfaceAttribute attribute.

This example shows how to apply the ClassInterfaceAttribute to a type, setting the ClassInterfaceType. Classes defined this way can be used from unmanaged COM.

using System;
using System.Runtime.InteropServices;

// Have the CLR expose a class interface (derived from IDispatch) for this type. 
// COM clients can call the  members of this class using the Invoke method from the IDispatch interface.
public class AClassUsableViaCOM
    public AClassUsableViaCOM() { }

    public Int32 Add(Int32 x, Int32 y) { return x + y; }

// The CLR does not expose a class interface for this type. 
// COM clients can call the members of this class using the methods from the IComparable interface.
public class AnotherClassUsableViaCOM : IComparable
    public AnotherClassUsableViaCOM() { }

    Int32 IComparable.CompareTo(Object o) { return 0; }

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

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