重写 ComboBox 改选择框样式

效果图片：

 public Form3()
        {
            InitializeComponent();
            comboBox1.Items.Add(new MyItem("1111111", this.GetImage("http://www.baidu.com/img/bdlogo.gif")));
            comboBox1.Items.Add(new MyItem("2222222", this.GetImage("http://www.baidu.com/img/bdlogo.gif")));
            comboBox1.Items.Add(new MyItem("3333333", this.GetImage("http://www.baidu.com/img/bdlogo.gif")));
            comboBox1.Items.Add(new MyItem("4444444", this.GetImage("http://www.baidu.com/img/bdlogo.gif")));
            comboBox1.Items.Add(new MyItem("5555555", this.GetImage("http://www.baidu.com/img/bdlogo.gif")));
            //默认选中项索引
            comboBox1.SelectedIndex = 0;
            //自绘组合框需要设置的一些属性
            comboBox1.DrawMode = DrawMode.OwnerDrawVariable;
            comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
            comboBox1.ItemHeight = 30;
            comboBox1.Width = 200;
            //添加DrawItem事件处理函数
            comboBox1.DrawItem += comboBox1_DrawItem;
        }

 点击ComboBox事件,找到comboBox_DrawItem

 private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            if ((e.State & DrawItemState.Selected) != 0)//鼠标选中在这个项上
            {
                //渐变画刷
                LinearGradientBrush brush = new LinearGradientBrush(e.Bounds, Color.FromArgb(255, 251, 237),
                    Color.FromArgb(255, 236, 181), LinearGradientMode.Vertical);
                //填充区域
                Rectangle borderRect = new Rectangle(3, e.Bounds.Y , e.Bounds.Width - 5, e.Bounds.Height - 2);

                e.Graphics.FillRectangle(brush, borderRect);
                //画边框
                Pen pen = new Pen(Color.FromArgb(229, 195, 101));
                e.Graphics.DrawRectangle(pen, borderRect);
            }
            else
            {
                SolidBrush brush = new SolidBrush(Color.FromArgb(217, 223, 230));
                e.Graphics.FillRectangle(brush, e.Bounds);
            }
            //获得项图片,绘制图片
            MyItem item = (MyItem)comboBox1.Items[e.Index];
            Image img = item.Img;
            //图片绘制的区域
            Rectangle imgRect = new Rectangle(6, e.Bounds.Y, 25, 25);
            e.Graphics.DrawImage(img, imgRect);
            //文本内容显示区域
            Rectangle textRect =
                new Rectangle(imgRect.Right, imgRect.Y, e.Bounds.Width - imgRect.Width, e.Bounds.Height - 2);
            //获得项文本内容,绘制文本
            String itemText = comboBox1.Items[e.Index].ToString();
            //文本格式垂直居中
            StringFormat strFormat = new StringFormat();
            strFormat.LineAlignment = StringAlignment.Center;
            e.Graphics.DrawString(itemText, new Font("宋体", 12), Brushes.Black, textRect, strFormat);
        }

 public class MyItem
        {
            //项文本内容
            private String Text;
            //项图片
            public Image Img;
            public MyItem(String text, Image img)
            {
                Text = text;
                Img = img;
            }
            //重写ToString函数，返回项文本
            public override string ToString()
            {
                return Text;
            }
        }
        public System.Drawing.Image GetImage(string strUrl)
        {
            try
            {
                string url = @"http://hiphotos.baidu.com/huyangdiy/pic/item/fd1d340bfaec3e656059f3df.jpg";
                url = strUrl;
                WebRequest request = WebRequest.Create(url);
                WebResponse response = request.GetResponse();
                Stream stream = response.GetResponseStream();

                Image image = Image.FromStream(stream);
                stream.Close();
                //g.DrawImage(image, 0, 0);
                //g.Dispose();
                return image;
            }
            catch { return null; }
        }