C# VSTO Powerpoint在上载时保持加载光标处于保留状态

我正在为powerpoint开发插件，用于将视频导出并上载到我的服务器。上传视频时，我想在PowerPoint上显示等待的光标。 我用过，这个很好用。但如果我按此使用计时器，就会出现光标变回默认值的问题

var vstoPresentation = Globals.ThisAddIn.Application.ActivePresentation;
vstoPresentation.CreateVideo("path\\to\\filename.mp4");

// Set cursor as hourglass
Cursor.Current = Cursors.WaitCursor;

System.Timers.Timer aTimer = new System.Timers.Timer();
aTimer.Elapsed += new ElapsedEventHandler((s, e) => {
    if (Globals.ThisAddIn.vstoPresentation.CreateVideoStatus == PowerPoint.PpMediaTaskStatus.ppMediaTaskStatusDone)
    {
        // Executing my time-intensive hashing code here...
        // uploading video to server

        // when upload finished
        // Set cursor as default arrow
        Cursor.Current = Cursors.Default;
    }
});
aTimer.Interval = 5000;
aTimer.Enabled = true;

---

最后，在许多博客上爬行，阅读官方文档，我找到了解决方案

var vstoPresentation = Globals.ThisAddIn.Application.ActivePresentation;

//declare a variable to check if video is uploading
public bool videoUploading = false;

//we need to register a "BeforeClose" handler 
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
    this.Application.PresentationBeforeClose += new EApplication_PresentationBeforeCloseEventHandler(Application_PowerPointBeforeClose);
}

internal void upload(){
    vstoPresentation.CreateVideo("path\\to\\filename.mp4");

    // Set cursor as hourglass
    Cursor.Current = Cursors.WaitCursor;

    System.Timers.Timer aTimer = new System.Timers.Timer();
    aTimer.Elapsed += new ElapsedEventHandler((s, e) => {
        if (Globals.ThisAddIn.vstoPresentation.CreateVideoStatus == PowerPoint.PpMediaTaskStatus.ppMediaTaskStatusDone)
        {
            Globals.ThisAddIn.videoUploading = true;

            // Executing my time-intensive hashing code here...
            // uploading video to server

            // when upload finished
            // Set cursor as default arrow
            Cursor.Current = Cursors.Default;
            Globals.ThisAddIn.videoUploading = false;
        }
    });
    aTimer.Interval = 5000;
    aTimer.Enabled = true;
}

private void Application_PowerPointBeforeClose(Presentation Pres, ref bool Cancel)
{
    if (Globals.ThisAddIn.videoUploading == true)
    {
        DialogResult dialogResult = MessageBox.Show("Video upload is in progress, are you sure you want to abort?", "My Addin", MessageBoxButtons.YesNo, MessageBoxIcon.Exclamation);
        if (dialogResult == DialogResult.No)
        {
            Cancel = true;
        }
    }
}