实现IDTExtensibility2和注册Add-In后，为何不能让Add-In在Office中显示？

虽然实现了IDTExtensibility2接口和注册了Add-In，但是在Office中仍然可能出现Add-In未显示的情况。这可能是因为没有正确定义Add-In的加载行为或没有指定正确的Office应用程序版本。

以下是一个示例，其中Add-In在Word和Excel中都可见，并且可以通过'工具”菜单中的'COM Add-Ins”对话框进行管理。

using System;
using Extensibility;
using Microsoft.Office.Core;
using Word = Microsoft.Office.Interop.Word;
using Excel = Microsoft.Office.Interop.Excel;

namespace MyAddIn
{
    public class Connect : IDTExtensibility2
    {
        private object _applicationObject;
        private object _addInInstance;

        public void OnConnection(object Application, ext_ConnectMode ConnectMode, object AddInInst, ref Array custom)
        {
            _applicationObject = Application;
            _addInInstance = AddInInst;

            if (ConnectMode == ext_ConnectMode.ext_cm_Startup)
            {
                // Define the add-in's load behavior
                var wordApp = _applicationObject as Word.Application;
                if (wordApp != null)
                {
                    var addIns = wordApp.AddIns;
                    var addIn = addIns.Add(Type: "MyAddIn", FileName: "C:\\MyAddIn.dll",
                        CopyFile: true, Install: true);
                    addIn.LoadBehavior = Word.wdLoadBehavior.wdLoadBehaviorLoadAtStartup;
                }

                var excelApp = _applicationObject as Excel.Application;
                if (excelApp != null)
                {
                    var addIns = excelApp.AddIns;
                    var addIn = addIns.Add(Type: "MyAddIn", FileName: "C:\\MyAddIn.dll",
                        CopyFile: true, Install: true);
                    addIn.AutoLoad = true;
                }
            }
        }

        public void OnDisconnection(ext_DisconnectMode DisconnectMode, ref Array custom)
        {
            // Clean up any objects, resources, etc.
        }

        public void OnAddInsUpdate(ref Array custom)
        {
            // Handle any changes to the list of add-ins
        }

        public void OnStartupComplete(ref Array custom)
        {
            // Perform any initialization required after Office has started up
        }

        public void OnBeginShutdown(ref Array custom)
        {
            // Perform any final tasks before shutting down
        }
    }
}

注意，此示例中的Add-In名称为'MyAddIn”，位于'C:\MyAddIn.dll”中。如果要在不同版本的