2018-11-19-WPF-在image控件用鼠标拖拽出矩形

    <Grid x:Name="Grid">
        <Image Source="TIM截图20180811150831.png"></Image>
        <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">欢迎访问我博客 http://lindexi.oschina.io </TextBlock>
        <Rectangle x:Name="Rectangle" StrokeThickness="2" Stroke="Black" HorizontalAlignment="Left" VerticalAlignment="Top"></Rectangle>
    </Grid>

            MouseDown += MainWindow_MouseDown;
            MouseMove += MainWindow_MouseMove;
            MouseUp += MainWindow_MouseUp;

        private void MainWindow_MouseDown(object sender, MouseButtonEventArgs e)
        {
            _started = true;

            _downPoint = e.GetPosition(Grid);
        }

        private bool _started;

        private Point _downPoint;

        private void MainWindow_MouseUp(object sender, MouseButtonEventArgs e)
        {
            _started = false;
        }

        private void MainWindow_MouseMove(object sender, MouseEventArgs e)
        {
            if (_started)
            {
                var point = e.GetPosition(Grid);

                var rect = new Rect(_downPoint, point);
                Rectangle.Margin = new Thickness(rect.Left, rect.Top, 0, 0);
                Rectangle.Width = rect.Width;
                Rectangle.Height = rect.Height;
            }
        }