WinForm实现ComboBox添加ToolTip悬浮文本提示功能

1.代码结构

2.实现代码

using System;
using System.Drawing;
using System.Windows.Forms;

namespace WinFormComboBoxWithTooltipDemo
{
    /// <summary>
    ///     WinForm 实现 ComboBox带有悬浮提示文本
    ///     LDH @ 2018-6-6
    /// </summary>
    public partial class FrmMain : Form
    {
        /// <summary>
        ///     ToolTip
        /// </summary>
        private readonly ToolTip _tip = new ToolTip();

        public FrmMain()
        {
            InitializeComponent();
        }

        private void FrmMain_Load(object sender, EventArgs e)
        {
            comboBox1.Items.Clear();

            comboBox1.Items.Insert(0, "第一");
            comboBox1.Items.Insert(1, "第二");
            comboBox1.Items.Insert(2, "第三");
            comboBox1.Items.Insert(3, "第四");

            comboBox1.DrawMode = DrawMode.OwnerDrawFixed;
            comboBox1.DrawItem += comboBox1_DrawItem;
            comboBox1.DropDownClosed += comboBox1_DropDownClosed;

            comboBox1.SelectedIndex = 1;
        }

        private void comboBox1_DropDownClosed(object sender, EventArgs e)
        {
            _tip.Hide(comboBox1);
        }

        private void comboBox1_DrawItem(object sender, DrawItemEventArgs e)
        {
            // 绘制背景
            e.DrawBackground();

            //  绘制列表项目
            e.Graphics.DrawString(comboBox1.Items[e.Index].ToString(), e.Font, Brushes.Black, e.Bounds);

            //  将高亮的列表项目的文字传递到toolTip1(之前建立ToolTip的一个实例)
            if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
            {
                _tip.Show(comboBox1.Items[e.Index].ToString(), comboBox1, e.Bounds.X + e.Bounds.Width,
                    e.Bounds.Y + e.Bounds.Height);
            }

            e.DrawFocusRectangle();
        }
    }
}

3.运行效果