附加到Office应用程序的运行实例时发生C#.NET错误

我正在使用C#Visual Studio 2012开发Excel加载项。我正在尝试获取Excel的应用程序对象的实例，以便跟踪当前活动的工作簿和工作表（ActiveWorkbook，ActiveWorksheet）。

我看到SO上的大多数其他相关问题都有建议使用以下内容的回复：

(Excel.Application)Marshal.GetActiveObject("Excel.Application");

我也尝试过使用这个：

(Excel.Application)Globals.ThisAddIn.Application;

在这两种情况下，我都会得到NullReferenceException。查看了此处建议的解决方法后：http://support.microsoft.com/kb/316125/en-us，我尝试了以下两种方法进行测试。

public CurrentSpreadSheet()
    {
        try
        {
            this.CurrentApplication = (Excel.Application)Globals.ThisAddIn.Application;
        }
        catch (NullReferenceException)
        {
            MessageBox.Show("Excel application object not registered. Trying plan B..");
            //Getting Excel's application object instance
            int iSection = 0, iTries = 0;
        tryAgain:
            try
            {
                iSection = 1; //Attempting GetActiveObject
                this.CurrentApplication = (Excel.Application)Marshal.GetActiveObject("Excel.Application");
                iSection = 0; //GetActiveObject succeeded so resume or go for normal error handling if needed
                this.CurrentApplication.Visible = true;
            }
            catch (Exception err)
            {
                System.Console.WriteLine("Visual C# .NET Error Attaching to Running Instance of Office Application .. yet.");
                if (iSection == 1)
                {
                    //GetObject may have failed because the
                    //Shell function is asynchronous; enough time has not elapsed
                    //for GetObject to find the running Office application. Wait
                    //1/2 seconds and retry the GetObject. If we try 20 times
                    //and GetObject still fails, we assume some other reason
                    //for GetObject failing and exit the procedure.
                    iTries++;
                    if (iTries < 20)
                    {
                        System.Threading.Thread.Sleep(500); // Wait 1/2 seconds.
                        goto tryAgain; //resume code at the GetObject line
                    }
                    else
                    {
                        MessageBox.Show("GetObject still failing.  Process ended.");
                    }
                }
                else
                {
                    //iSection == 0 so normal error handling
                    MessageBox.Show(err.Message);
                }
            }
        }

    }

输出为：

Excel application object not registered. Trying plan B..
GetObject still failing.  Process ended.

在极少数情况下，"B计划"确实有效；我看不到第二个消息框。CurrentSpreadSheet是一个单例，我打算在启动期间从提供的类ThisAddIn更新它。

在这个插件中，我有一些类似的东西：

private CurrentSpreadSheet css = CurrentSpreadSheet.Instance;
private void ThisAddIn_Startup(object sender, System.EventArgs e)
    {
        ///...Some code
        css.updateCurrentSpreadSheet();
}

有没有更好的方法来获取Application对象？如果在启动过程中无法做到这一点，有没有更好的方法可以让我从excel/我的加载项启动时就跟踪当前活动的工作表/工作簿？目前，我依靠应用程序对象（例如(Excel.Workbook)this.CurrentApplication.ActiveWorkbook;）和一些事件处理程序来跟踪当前工作簿和工作表。

我尝试使用ExcelDNA:

this.CurrentApplication = (Excel.Application)ExcelDna.Integration.ExcelDnaUtil.Application;

这在某些情况下有效，但大多数情况下会出现以下错误：

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> ExcelDna.Integration.XlCallException: Exception of type 'ExcelDna.Integration.XlCallException' was thrown.