使用C#接口和P/Invoke更改C# WinForms ComboBox.SelectedIndex时，如何使SelectedIndexChanged触发器？

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WinFormsApp
{
    public partial class MainForm : Form
    {
        // P/Invoke声明
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)]
        public static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);

        // ComboBox的消息常量
        private const int CB_SETCURSEL = 0x014E;
        private const int WM_REFLECT = 0x2000;
        private const int WM_COMMAND = 0x0111;
        private const int CBN_SELCHANGE = 1;

        // 保存当前的SelectedIndex值
        private int previousSelectedIndex;

        public MainForm()
        {
            InitializeComponent();
        }

        private void ChangeSelectedIndex(int newIndex)
        {
            // 保存当前的SelectedIndex值
            previousSelectedIndex = comboBox.SelectedIndex;

            // 使用P/Invoke更改SelectedIndex属性
            SendMessage(comboBox.Handle, CB_SETCURSEL, (IntPtr)newIndex, IntPtr.Zero);

            // 检查新的SelectedIndex值是否与之前保存的值不同
            if (comboBox.SelectedIndex != previousSelectedIndex)
            {
                // 手动触发SelectedIndexChanged事件
                SendMessage(comboBox.Handle, WM_REFLECT + WM_COMMAND, (IntPtr)(CBN_SELCHANGE << 16), comboBox.Handle);
            }
        }

        private void button_Click(object sender, EventArgs e)
        {
            // 示例：将ComboBox的SelectedIndex更改为2
            ChangeSelectedIndex(2);
        }
    }
}