private void Remove_TestTask(object sender, RoutedEventArgs e)
 {
     if (DataModel.IsRunning)
     {
         _ = MessageBox.Show("任务开始后无法修改。", "WARNING");
     }
     else
     {
         DataModel.Tasks.Remove(TestTaskTree.SelectedItem as TestTask);
         if (DataModel.Tasks.Count == 0)
         {
             DataContext = null;
             DataModel   = new MainWindowModel();
             DataContext = DataModel;
         }
     }
 }
 private void Close_MenuItem_Click(object sender, RoutedEventArgs e)
 {
     DataContext = null;
     DataModel   = new MainWindowModel();
     DataContext = DataModel;
 }