最后，这一招奏效了：

protected override void OnContentRendered(EventArgs e)
        {
            base.OnContentRendered(e);
            MoveBottomRightEdgeOfWindowToMousePosition();
        }

        private void MoveBottomRightEdgeOfWindowToMousePosition()
        {
            var transform = PresentationSource.FromVisual(this).CompositionTarget.TransformFromDevice;
            var mouse = transform.Transform(GetMousePosition());
            Left = mouse.X - ActualWidth;
            Top = mouse.Y - ActualHeight;
        }

        public System.Windows.Point GetMousePosition()
        {
            System.Drawing.Point point = System.Windows.Forms.Control.MousePosition;
            return new System.Windows.Point(point.X, point.Y);
        }

你能不能不要用这样的东西？：

Point mousePositionInApp = Mouse.GetPosition(Application.Current.MainWindow);
Point mousePositionInScreenCoordinates = 
    Application.Current.MainWindow.PointToScreen(mousePositionInApp);

我还没能测试它，但我认为它应该工作。
更新〉〉〉
你不必在这些方法中使用Application.Current.MainWindow作为参数...如果你在处理程序中可以访问一个Button或另一个UIElement，它 * 应该 * 仍然可以工作：

Point mousePositionInApp = Mouse.GetPosition(openButton);
Point mousePositionInScreenCoordinates = openButton.PointToScreen(mousePositionInApp);

同样，我还没有能够测试这个，但如果它也失败了，那么你可以在How do I get the current mouse screen coordinates in WPF?帖子中找到另一个方法。

您也可以通过稍微修改初始示例并在显示窗口之前定位窗口来完成此操作。

MyWindowObjectThatInheritsWindow window = new MyWindowObjectThatInheritsWindow();

var helper = new WindowInteropHelper(window);
var hwndSource = HwndSource.FromHwnd(helper.EnsureHandle());
var transformFromDevice = hwndSource.CompositionTarget.TransformFromDevice;

System.Windows.Point wpfMouseLocation = transformFromDevice.Transform(GetMousePositionWindowsForms());
window.Left = wpfMouseLocation.X - 300;
window.Top = wpfMouseLocation.Y - 240;
window.Show();

你也可以这样做：

private void Button_Click(object sender, RoutedEventArgs e)
{
    ConfigWindow cw = new ConfigWindow();
    var transform = PresentationSource.FromVisual(this).CompositionTarget.TransformFromDevice;
    var mouse = transform.Transform(GetMousePosition());
    cw.WindowStartupLocation = WindowStartupLocation.Manual;
    cw.Left = mouse.X - cw.ActualWidth;
    cw.Top = mouse.Y - cw.ActualHeight;
    cw.Show();
}

public System.Windows.Point GetMousePosition()
{
    System.Drawing.Point point = System.Windows.Forms.Control.MousePosition;
    return new System.Windows.Point(point.X, point.Y);
}