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CA1412: Mark ComSource Interfaces as IDispatch

  • Article
Item Value
RuleId CA1412
Category Microsoft.Interoperability
Breaking change Breaking

Cause

A type is marked with the ComSourceInterfacesAttribute attribute and at least one specified interface is not marked with the InterfaceTypeAttribute attribute set to the InterfaceIsDispatch value.

Rule description

ComSourceInterfacesAttribute is used to identify the event interfaces that a class exposes to Component Object Model (COM) clients. These interfaces must be exposed as InterfaceIsIDispatch to enable Visual Basic 6 COM clients to receive event notifications. By default, if an interface is not marked with the InterfaceTypeAttribute attribute, it is exposed as a dual interface.

How to fix violations

To fix a violation of this rule, add, or modify the InterfaceTypeAttribute attribute so that its value is set to InterfaceIsIDispatch for all interfaces that are specified with the ComSourceInterfacesAttribute attribute.

When to suppress warnings

Do not suppress a warning from this rule.

Example

The following example shows a class where one of the interfaces violates the rule.

using System;
using System.Runtime.InteropServices;

[assembly: ComVisible(true)]
namespace InteroperabilityLibrary
{
   // This violates the rule for type EventSource.
   [InterfaceType(ComInterfaceType.InterfaceIsDual)]
   public interface IEventsInterface
   {
      void EventOne();
      void EventTwo();
   }

   // This satisfies the rule.
   [InterfaceType(ComInterfaceType.InterfaceIsIDispatch)]
   public interface IMoreEventsInterface
   {
      void EventThree();
      void EventFour();
   }

   [ComSourceInterfaces(
      "InteroperabilityLibrary.IEventsInterface\0" + 
      "InteroperabilityLibrary.IMoreEventsInterface")]
   public class EventSource
   {
      // Event and method declarations.
   }
}

CA1408: Do not use AutoDual ClassInterfaceType

See also