在 C# 中使用画笔

　　
　　public class Rectangle : Shape
　　{
　　protected Point m_Start;
　　protected Point m_End;
　　public Rectangle(Point start, Point end, Color fgColor)
　　{
　　m_Start = start;
　　m_End = end;
　　m_Color = fgColor;
　　}
　　public override void Draw(Form canvas)
　　{
　　if (canvas == null)
　　{
　　return;
　　}
　　InitializeGraphics(canvas);
　　Point startPoint = canvas.PointToScreen(m_Start);
　　Point endPoint = canvas.PointToScreen(m_End);
　　MainForm mainForm = (MainForm)canvas;
　　Color bgColor = GetBackgroundColor(m_Color);
　　Size rectSize = new Size(m_End.X - m_Start.X, m_End.Y - m_Start.Y);
　　System.Drawing.Rectangle rectToDraw = new System.Drawing.Rectangle(startPoint, rectSize);
　　ControlPaint.DrawReversibleFrame(rectToDraw, bgColor, FrameStyle.Thick);
　　}
　　}