绘制圆角矩形（方法 ）

/*  
  sharecodes.org 友情提醒：尊重知识，转载请注明原创作者、出处！  
*/  

/// <summary>   
/// C# GDI+ 绘制圆角矩形   
/// </summary>   
/// <param name="g">Graphics 对象</param>   
/// <param name="rectangle">Rectangle 对象，圆角矩形区域</param>   
/// <param name="borderColor">边框颜色</param>   
/// <param name="borderWidth">边框宽度</param>   
/// <param name="r">圆角半径</param>   
public static void DrawRoundRectangle(Graphics g, Rectangle rectangle, Color borderColor, float borderWidth, int r)   
{   
    // 如要使边缘平滑，请取消下行的注释   
    // g.SmoothingMode = SmoothingMode.HighQuality;   

    // 由于边框也需要一定宽度，需要对矩形进行修正   
    rectangle = new Rectangle(rectangle.X, rectangle.Y, rectangle.Width - 1, rectangle.Height - 1);   
    Pen p = new Pen(borderColor, borderWidth);   
    // 调用 getRoundRectangle 得到圆角矩形的路径，然后再进行绘制   
    g.DrawPath(p, getRoundRectangle(rectangle, r));   
}   

/// <summary>   
/// 根据普通矩形得到圆角矩形的路径   
/// </summary>   
/// <param name="rectangle">原始矩形</param>   
/// <param name="r">半径</param>   
/// <returns>图形路径</returns>   
private static GraphicsPath getRoundRectangle(Rectangle rectangle, int r)   
{   
    int l = 2 * r;   
    // 把圆角矩形分成八段直线、弧的组合，依次加到路径中   
    GraphicsPath gp = new GraphicsPath();   
    gp.AddLine(new Point(rectangle.X + r, rectangle.Y), new Point(rectangle.Right - r, rectangle.Y));   
    gp.AddArc(new Rectangle(rectangle.Right - l, rectangle.Y, l, l), 270F, 90F);   

    gp.AddLine(new Point(rectangle.Right, rectangle.Y + r), new Point(rectangle.Right, rectangle.Bottom - r));   
    gp.AddArc(new Rectangle(rectangle.Right - l, rectangle.Bottom - l, l, l), 0F, 90F);   

    gp.AddLine(new Point(rectangle.Right - r, rectangle.Bottom), new Point(rectangle.X + r, rectangle.Bottom));   
    gp.AddArc(new Rectangle(rectangle.X, rectangle.Bottom - l, l, l), 90F, 90F);   

    gp.AddLine(new Point(rectangle.X, rectangle.Bottom - r), new Point(rectangle.X, rectangle.Y + r));   
    gp.AddArc(new Rectangle(rectangle.X, rectangle.Y, l, l), 180F, 90F);   
    return gp;   
}  

/*    sharecodes.org 友情提醒：尊重知识，转载请注明原创作者、出处！  */    // 在 Form 上放置一 Panel，命名为 panel1，调用绘图方法   DrawRoundRectangle(panel1.CreateGraphics(), new Rectangle(10, 10, 100, 80), ColorTranslator.FromHtml("#CCFF66"), 4F, 20);   DrawRoundRectangle(panel1.CreateGraphics(), new Rectangle(120, 10, 100, 80), ColorTranslator.FromHtml("#FF66FF"), 4F, 20);   DrawRoundRectangle(panel1.CreateGraphics(), new Rectangle(240, 10, 100, 80), ColorTranslator.FromHtml("#6699FF"), 4F, 20);