Office COM add-in 开发(一)

     Office 的 add-in 分为两类，一类是application add-in，一类是 COM add-in. COM add-in 是一个进程内的COM server，需要实现 IDTExensibility2 接口 。该接口定义在Msaddndr.dll (Microsoft add-in designer type library) 中，该接口有五个成员函数。

    1. OnConnection(IDispatch *pApplication, AddInDesignerObjects::ext_ConnectMode  ConnectMode, IDispatch *pAddInInst, SAFEARRAY ** custom )
        当 add-in 被加载的时候，这个函数会被触发。 如果函数返回成功，那么add-in会继续加载，如果返回失败，则add-in 会停止加载，add-in 对象会被删除。

•            IDispatch * pApplication: reference to the host application object.
•            AddInDesignerObjects::ext_ConnectMode: 

                                 - ext_cm_AfterStartup: The add-in is started by the end user from the COM Add-ins dialog box.
                                 - ext_cm_CommandLine: The add-in is connected from the command line. Note that this does not apply to building COM add-ins for Office applications.
                                - ext_cm_External: The add-in is connected by an external application through Automation. Note that this does not apply to building COM add-ins for Office applications.
                                 - ext_cm_Startup: The add-in is started by the host at application startup. This behavior is controlled by a setting in the registry.

•     IDispatch *pAddInInst: A reference to the COMAddIn object that refers to this add-in in the  COMAddIns collection for the host application.  
•     SAFEARRAY ** : An array of Variant type values that can hold user-defined data.

   2. OnDisconnection(AddInDesignerObjects::ext_DisconnectMode  RemoveMode, SAFEARRAY ** custom )
      当 add-in 被卸载的时候，这个函数会被触发。

•      AddInDesignerObjects::ext_DisconnectMode RemoveMode: 

      - ext_dm_HostShutdown: The add-in is disconnected when the host application closes.
         - ext_dm_UserClosed: The add-in is disconnected by the end user or an Automation controller.


 3. OnStartupComplete (SAFEARRAY ** custom )：add-in 加载结束的时候会调用
     OnBeginShutdown (SAFEARRAY ** custom ) : 开始卸载 add-in 的时候会调用

    COM add-in 除了普通COM 的注册的过程，还会在：HKEY_CURRENT_USER\Software\Microsoft\Office\<OfficeApp>\Addins\<ProgID> 注册。在这个键(key)下面，有一个属性 LoadBehavior 是用来定义 add-in 被加载的方式。

• 0 = Disconnect - Is not loaded.
• 1 = Connected - Is loaded.
• 2 = Bootload - Load on application startup.
• 8 = DemandLoad - Load only when requested by user.
• 16 = ConnectFirstTime - Load only once (on next startup).
• The typical value specified is 0x03 (Connected | Bootload).