C# 自定义 下拉框

using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;
using System.Drawing;

namespace Custom
{
    public class CustomComBoBox : ComboBox
    {
        private Color borderColor;

        /// <summary>
        /// 边框颜色
        /// </summary>
        public Color BorderColor
        {
            get { return borderColor; }
            set { borderColor = value; }
        }

        protected override void WndProc(ref Message m)
        {
            base.WndProc(ref m);
            ControlPaint.DrawBorder(this.CreateGraphics(), this.ClientRectangle, this.BorderColor, ButtonBorderStyle.Solid);
        } 
    }
}