sharpMap开发中，自定义控件拖动后，会有残影！！求解决方案

[qq_34048603]

代码如下：

 private void mapBox1_MouseMove(GeoAPI.Geometries.Coordinate worldPos, MouseEventArgs imagePos)
        {
            PointF TemplatePos;//用于记录从地图坐标转换到桌面坐标的坐标
            int x, y;
            this.label1.Text = worldPos.X.ToString("N4") + "/" + worldPos.Y.ToString("N4");
            this.label2.Text = imagePos.X.ToString("N4") + "/" + imagePos.Y.ToString("N4");
            if (IsMousedowm)
            {
                TemplatePos = mapBox1.Map.WorldToImage(MouseoldPos);
                x = (int)TemplatePos.X;
                y = (int)TemplatePos.Y;
                a.orgPointLable.X = x;
                a.orgPointLable.Y = y;
                a.Location = new Point(x, y);
                mapBox1.Refresh();
            }
        }

        private void mapBox1_MouseDown(GeoAPI.Geometries.Coordinate worldPos, MouseEventArgs imagePos)
        {
            float x, y;
            x = a.orgPointLable.X;
            y = a.orgPointLable.Y;
            IsMousedowm = true;
            MouseoldPos = mapBox1.Map.ImageToWorld(new PointF(x, y));
        }

显示的效果是这样：
这些红色控件是复制的，里面是有属性的。求大神指教！1