COMAddIn.Object始终为空

Question

我正在尝试使用VSTO Outlook AddIn实现电子邮件功能。但我得到的ComAddIn.Object始终为空，因此我无法访问VSTO AddIns的成员

  Outlook.Application OutlookObj = new Outlook.Application();
        object AddinName = "OutlookAddIn";
        COMAddIn AddIn = OutlookObj.COMAddIns.Item(ref AddinName);
        IOutLookApp utils = (IOutLookApp)AddIn.Object;
        utils.CallOlMethod();

这是TheAddIn.cs

namespace OutlookAddIn
{
public interface IOutLookApp
{
    void CallOlMethod();
}  

public partial class ThisAddIn
{
    protected override object RequestComAddInAutomationService()
    {
        OutlookApp ol = new OutlookApp();
        return ol;
    }
    #region VSTO generated code
    private void ThisAddIn_Startup(object sender, System.EventArgs e)
    {
    }

    private void ThisAddIn_Shutdown(object sender, System.EventArgs e)
    {
        // Note: Outlook no longer raises this event. If you have code that 
        //    must run when Outlook shuts down, see 
    https://go.microsoft.com/fwlink/?LinkId=506785
    }
    /// <summary>
    /// Required method for Designer support - do not modify
    /// the contents of this method with the code editor.
    /// </summary>
    private void InternalStartup()
    {
        this.Startup += new System.EventHandler(ThisAddIn_Startup);
        this.Shutdown += new System.EventHandler(ThisAddIn_Shutdown);
    }
#endregion
public void CreateOutlookItem()
{
    Outlook.MailItem newEmail = new Outlook.MailItem
    {
        To = "example@gmail.com",
        Subject = "testing",
        Importance = Outlook.OlImportance.olImportanceLow
    };
    newEmail.Send();
}
}
public class OutlookApp:
   StandardOleMarshalObject,
    IOutLookApp
{
    public void CallOlMethod()
    {
        Globals.ThisAddIn.CreateOutlookItem();
    }
}
}

我在这里做错了什么？虽然我的AddIn类是公开的，但是ComAddIn.Object仍然是空的，为什么呢？请帮助解决这个问题。

Answer 1

要向外部调用者公开您的VSTO外接程序，请执行以下步骤：

1. 将接口定义为dual并使其COM可见[ComVisible(true)] [InterfaceType(ComInterfaceType.InterfaceIsDual)] public interface IOutLookApp { void CallOlMethod(); }
2. 还定义了一个实现该接口的类，如下所示[ComVisible(true)] [ClassInterface(ClassInterfaceType.None)] public class OutlookApp : StandardOleMarshalObject, IOutLookApp { public void CallOlMethod() { //do something } }

阅读更多：Call code in VSTO Add-ins from other Office solutions和VSTO Add-ins, COMAddIns and RequestComAddInAutomationService

编辑:还需要检查项目设置中的“注册Com interop"，并确保以管理员身份运行Visual Studio。