C# winform combobox 扩展

先看看效果：

先构造一个子项的类：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;//

namespace ComboBox_Draw
{
    //自定义组合框项
    class MyItem
    {
        //项文本内容
        private String Text;
       
        //项图片
        public Image Img;

        //构造函数
        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;
        }
    }
}

然后看重写DrawItem事件：

private void ComboBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            //鼠标选中在这个项上
            if ((e.State & DrawItemState.Selected) != 0)
            {
                //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(255, 255, 255));
                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 + 3, 45,45);
            e.Graphics.DrawImage(img, imgRect);
            
            //文本内容显示区域
            Rectangle textRect =
                    new Rectangle(imgRect.Right + 2, 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("微软雅黑", 12), Brushes.Black, textRect, strFormat);
        }

最后是窗体Load事件：最后是窗体Load事件：

        private void Form1_Load(object sender, EventArgs e)
        {
            //添加项
            comboBox1.Items.Add(new MyItem("000000", Image.FromFile(Application.StartupPath + "\0.gif")));
            comboBox1.Items.Add(new MyItem("111111", Image.FromFile(Application.StartupPath + "\1.gif")));
            comboBox1.Items.Add(new MyItem("222222", Image.FromFile(Application.StartupPath + "\2.gif")));
            comboBox1.Items.Add(new MyItem("333333", Image.FromFile(Application.StartupPath + "\3.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.OwnerDrawFixed;
            comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
            comboBox1.ItemHeight = 50;
            comboBox1.Width = 200;

            //添加DrawItem事件处理函数
            comboBox1.DrawItem += ComboBox1_DrawItem;

        }