WPF左键单击并拖动

所以这个代码:

    private void NewButton_MouseDown(object sender, MouseButtonEventArgs e)
    {
        var test = e.LeftButton;
        var test2 = e.RightButton;
        if (!bButtonIsDown)
        {
            bButtonIsDown = true;
            Button mover = (Button)sender;
            pntEnterPoint = e.GetPosition(this.cnvsLinkScreen);

            cnvsLinkScreen.MouseMove += CnvsLinkScreen_MouseMove;
            cnvsLinkScreen.MouseUp += CnvsLinkScreen_MouseUp;
            
            spMover = (StackPanel)((Button)sender).Parent;
            pntPreviousPoint.X = Canvas.GetLeft(spMover);
            pntPreviousPoint.Y = Canvas.GetTop(spMover);

        }
    }

    private void NewButton_MouseMove(object sender, MouseEventArgs e)
    {
        Button mover = (Button)sender;
        StackPanel spMover = (StackPanel)((Button)sender).Parent; 
        base.OnMouseMove(e);
        if (e.LeftButton == MouseButtonState.Pressed)
        {

            // Inititate the drag-and-drop operation.
            FindChild<StackPanel>(cnvsLinkScreen, "CSVImport");
            pntEnterPoint = e.GetPosition(this.cnvsLinkScreen);
            Canvas.SetLeft(spMover, pntEnterPoint.X + 1);
            Canvas.SetTop(spMover, pntEnterPoint.Y + 1);
        }
    }

工作,但只有右键。启用事件处理程序时:

newButton.MouseDown += NewButton_MouseDown;

我已经做了大量的阅读,人们会引用previewMouseLeftButtonDown事件处理程序,但是当我在适当的地方使用它(相同的代码)时cnvsLinkScreen.MouseMove+=CnvsLinkScreen_MouseMove在我松开鼠标左键(向上键)之前不会启动,然后StackPanel拖动,直到我单击并放下它。

为什么MouseDown事件处理程序在鼠标左键按下时不触发,而只在鼠标右键按下时触发?