You can apply this attribute to classes.

You apply this attribute to a managed class to identify the event interfaces that the class exposes as COM connection points. An event interface contains methods that map to the event members of the class. The class event name and the interface method name must be the same. This attribute can accommodate up to four source interfaces for a class by passing the type of the source interface to the appropriate constructor, which take between one and four type arguments. For classes that want to expose more than four source interfaces, the string version of the constructor can be used. For additional information about exposing.NET events to COM clients, see How to: Raise Events Handled by a COM Sink.

The following example shows how to apply the ComSourceInterfacesAttribute to connect the event sink interface to a class by passing the namespace and event sink interface.

Imports System.Runtime.InteropServices

<ComSourceInterfacesAttribute("ButtonEventsLib.ButtonEvents, ButtonEventsLib")> _
public Class Baz
    'Insert code here.
End Class

using System.Runtime.InteropServices;

[ComSourceInterfacesAttribute("ButtonEventsLib.ButtonEvents, ButtonEventsLib")]
public class Baz 
{
   //Insert code here.
}

using namespace System::Runtime::InteropServices;

[ComSourceInterfacesAttribute("ButtonEventsLib.ButtonEvents, ButtonEventsLib")]
public ref class Baz{};

import System.Runtime.InteropServices;

ComSourceInterfacesAttribute("ButtonEventsLib.ButtonEvents, ButtonEventsLib") public class Baz 
{
   //Insert code here.
}

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

.NET Framework

.NET Compact Framework

Reference