效果如下图，本人网上搜索资料加上自己的研究终于实现了在combobox子项中加上删除按钮。

一、窗体中的代码：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Text;using System.Windows.Forms;using System.Runtime.InteropServices;using System.Drawing.Drawing2D;namespace ComboBoxEx{    public partial class Form1 : Form    {        [DllImport("user32")]        private static extern int GetComboBoxInfo(IntPtr hwnd, out COMBOBOXINFO comboInfo);        struct RECT        {            public int left, top, right, bottom;        }        struct COMBOBOXINFO        {            public int cbSize;            public RECT rcItem;            public RECT rcButton;            public int stateButton;            public IntPtr hwndCombo;            public IntPtr hwndItem;            public IntPtr hwndList;        }        private void Form1_Load(object sender, EventArgs e)        {            comboBox1.DrawMode = DrawMode.OwnerDrawFixed;            comboBox1.Items.Add(new comboItem("sgset", pictureBox1.Image));            comboBox1.Items.Add(new comboItem("sdgsdg", pictureBox1.Image));            comboBox1.Items.Add(new comboItem("sdgsdg", pictureBox1.Image));        }        public Form1()        {            InitializeComponent();            comboBox1.HandleCreated += (s, e) =>            {                COMBOBOXINFO combo = new COMBOBOXINFO();                combo.cbSize = Marshal.SizeOf(combo);                GetComboBoxInfo(comboBox1.Handle, out combo);                hwnd = combo.hwndList;                init = false;            };        }        bool init;        IntPtr hwnd;        NativeCombo nativeCombo = new NativeCombo();        //This is to store the Rectangle info of your Icons        //Key:  the Item index        //Value: the Rectangle of the Icon of the item (not the Rectangle of the item)        Dictionary
     
       dict = new Dictionary
      
       ();        public class NativeCombo : NativeWindow        {            //this is custom MouseDown event to hook into later            public event MouseEventHandler MouseDown;            protected override void WndProc(ref Message m)            {                if (m.Msg == 0x201)//WM_LBUTTONDOWN = 0x201                {                    int x = m.LParam.ToInt32() & 0x00ff;                    int y = m.LParam.ToInt32() >> 16;                    if (MouseDown != null) MouseDown(null, new MouseEventArgs(MouseButtons.Left, 1, x, y, 0));                }                base.WndProc(ref m);            }        }        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(0, e.Bounds.Y, e.Bounds.Width, 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            comboItem item = (comboItem)comboBox1.Items[e.Index];            Image img = item.Img;            //图片绘制的区域            Rectangle imgRect = new Rectangle(e.Bounds.Width - 18, e.Bounds.Y, 15, 15);            dict[e.Index] = imgRect;            if (img != null && (e.State & DrawItemState.Selected) != 0)            {                e.Graphics.DrawImage(img, imgRect);            }            Rectangle textRect =                new Rectangle(10, imgRect.Y, e.Bounds.Width - imgRect.Width, e.Bounds.Height + 2);            string itemText = comboBox1.Items[e.Index].ToString();            StringFormat strFormat = new StringFormat();            strFormat.LineAlignment = StringAlignment.Center;            e.Graphics.DrawString(itemText, new Font("宋体", 14), Brushes.Black, textRect, strFormat);        }        private void comboBox1_DropDown(object sender, EventArgs e)        {            if (!init)            {                //Register the MouseDown event handler <--- THIS is WHAT you want.                nativeCombo.MouseDown += comboListMouseDown;                nativeCombo.AssignHandle(hwnd);                init = true;            }        }        //This is the MouseDown event handler to handle the clicked icon        private void comboListMouseDown(object sender, MouseEventArgs e)        {            foreach (var kv in dict)            {                if (kv.Value.Contains(e.Location))                {                    //Show the item index whose the corresponding icon was held down                    MessageBox.Show(kv.Key.ToString());                    return;                }            }        }    }}
      
     

二、子项辅助类

using System;using System.Collections.Generic;using System.Text;using System.Drawing;namespace ComboBoxEx{    public class comboItem : object    {        private Image img = null;        private string text = null;        public comboItem()        {        }        public comboItem(string text)        {            Text = text;        }        public comboItem(string text,Image img)        {            Text = text;            Img = img;        }        // item Img        public Image Img        {            get            {                return img;            }            set            {                img = value;            }        }        // item text        public string Text        {            get            {                return text;            }            set            {                text = value;            }        }        // ToString() should return item text        public override string ToString()        {            return text;        }    }}