Modify your extension's header file

1. Unless you are going to use it for administering your component from a property page, you can remove the default inheritance and COM_INTERFACE_ENTRY for the default interface.
2. Add the Chat callback interface to your new objects inheritance.
   For example:

   class ATL_NO_VTABLE CCustomCmd : 
      public CComObjectRootEx<CComSingleThreadModel>,
      public CComCoClass<CCustomCmd, &CLSID_CustomCmd>,
      public IDispatchImpl<IChatExtensionCallBack, 
   &IID_IChatExtensionCallBack, &LIBID_CHATSVCLib>,
      public IDispatchImpl<IChatServerCallBack, 
   &IID_IChatServerCallBack, &LIBID_CHATSVCLib>   
   

3. Add COM_INTERFACE_ENTRY for each of the chat callback interfaces.
   For example:

   BEGIN_COM_MAP(CCustomCmd)
      COM_INTERFACE_ENTRY(IChatExtensionCallBack)
      COM_INTERFACE_ENTRY(IChatServerCallBack)
   END_COM_MAP()
   

4. Add definitions for each of the pure virtual methods in the callback interfaces. A complete definition of the callback interfaces can be found in the sample file vc5\msgfilter\MessageFilter.h. Copy the ones you need into your project.

Note: All interface methods must be defined, but can return a "Not implemented" (E_NOTIMPL) error if they are not required.

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