using System;using System.Collections.Generic;using System.ComponentModel;using System.Diagnostics;using System.Text;using System.Windows.Forms;using System.Drawing.Drawing2D;using System.Drawing;namespace POS.Controls{    public partial class PosPanel : Panel    {        public PosPanel()        {            InitializeComponent();        }        private int mMatrixRound = 8;        private Color mBack;        public Color Back        {            get { return mBack; }            set            {                if (value == null)                {                    mBack = Control.DefaultBackColor;                }                else                {                    mBack = value;                }                base.Refresh();            }        }        public int MatrixRound        {            get { return mMatrixRound; }            set            {                mMatrixRound = value;                base.Refresh();            }        }         private GraphicsPath CreateRound(Rectangle rect, int radius)        {            GraphicsPath roundRect = new GraphicsPath();            //顶端             roundRect.AddLine(rect.Left + radius - 1, rect.Top - 1, rect.Right - radius, rect.Top - 1);            //右上角             roundRect.AddArc(rect.Right - radius, rect.Top - 1, radius, radius, 270, 90);            //右边             roundRect.AddLine(rect.Right, rect.Top + radius, rect.Right, rect.Bottom - radius);            //右下角            roundRect.AddArc(rect.Right - radius, rect.Bottom - radius, radius, radius, 0, 90);            //底边             roundRect.AddLine(rect.Right - radius, rect.Bottom, rect.Left + radius, rect.Bottom);            //左下角             roundRect.AddArc(rect.Left - 1, rect.Bottom - radius, radius, radius, 90, 90);            //左边             roundRect.AddLine(rect.Left - 1, rect.Top + radius, rect.Left - 1, rect.Bottom - radius);            //左上角             roundRect.AddArc(rect.Left - 1, rect.Top - 1, radius, radius, 180, 90);            return roundRect;        }        protected override void OnPaint(PaintEventArgs e)        {            int width = base.Width - base.Margin.Left - base.Margin.Right;            int height = base.Height - base.Margin.Top - base.Margin.Bottom;            Rectangle rec = new Rectangle(base.Margin.Left, base.Margin.Top, width, height);            GraphicsPath round = CreateRound(rec, mMatrixRound);            e.Graphics.SmoothingMode = SmoothingMode.AntiAlias;            e.Graphics.FillPath((Brush)(new SolidBrush(mBack)), round);        }     }}

使用的时候背景颜色设为透明，Back是前景色，设一个不同的颜色。就OK了