c# - UI 线程未按预期刷新为 WPF 表单

Question

我在此 RelayCommand 中遇到 UI 刷新问题:

private RelayCommand _DeleteReferenceCommand;
public RelayCommand DeleteReferenceCommand
{
    get
    {
        return _DeleteReferenceCommand ?? (_DeleteReferenceCommand = new RelayCommand(
            () =>
              {
                 //the 2 next lines trigger properties that will modify some components Visibility on the view
                 ReferencesGridWithPicsUC.TextReplacingGridView = "Deleting the reference. Please wait...";
                 ReferencesGridWithPicsUC.GridViewVisibility = false;
                System.Windows.Forms.Cursor.Current = System.Windows.Forms.Cursors.WaitCursor; // mouse cursor change


               //using multi-threading so that UI updates while a long process takes place in the background
               Task.Run(() =>
               {
                  Application.Current.Dispatcher.Invoke((new Action(() =>
                  {
                    System.Threading.Thread.Sleep(3000); // simulates a long process
                    ReferencesGridWithPicsUC.GridViewVisibility = true; // Sets the UI controls visibility back to previous state
                    System.Windows.Forms.Cursor.Current = System.Windows.Forms.Cursors.Hand; // Mouse cursor back to previous value
                 }
              )));
           }
       );
     },
     () => { return ReferencesGridWithPicsUC.SelectedReference != null; }
    ));
  }
}

具体来说，当我启动应用程序并首次运行此代码时，它按预期工作(鼠标光标和控件在 Sleep(3000) 之前按预期更新，之后恢复正常。再次执行代码时，我可以看到该属性已正确更新 GridViewVisibility 。但 UI 不再刷新:由 GridViewVisibility 更改触发的控件可见性未更新。另一方面，鼠标光标按预期不断更新....

如果有人能解开这个该死的谜题，那我就欠你的了;)

Answer 1

您必须仅调用 Dispatcher 来更新 UI。

为后台任务使用Task.Run。

await Task.Run(() =>
    {
        Thread.Sleep(3000);
    });

在异步委托(delegate)中

new RelayCommand(
          async () =>
          {

之后，您将回到 UI 线程中，因此不再需要 Dispatcher。