c# winform 自动关闭messagebox 模拟回车

 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; 

 namespace WindowsApplication1
 {
     public partial class AutoDeleteMessageBox : Form
     {
         [DllImport("user32.dll", EntryPoint = "FindWindow", CharSet = CharSet.Auto)]
         private extern static IntPtr FindWindow(string lpClassName, string lpWindowName); 

         [DllImport("user32.dll", CharSet = CharSet.Auto)]
         public static extern int PostMessage(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam); 

         public const int WM_CLOSE = 0x10; 

         public AutoDeleteMessageBox()
         {
             InitializeComponent();
         } 

         private void button1_Click(object sender, EventArgs e)
         {
             StartKiller();
             MessageBox.Show("3秒钟后自动关闭MessageBox窗口", "MessageBox");
         } 

         private void StartKiller()
         {
             Timer timer = new Timer();
             timer.Interval = ; //3秒启动
             timer.Tick += new EventHandler(Timer_Tick);
             timer.Start();
         } 

         private void Timer_Tick(object sender, EventArgs e)
         {
             KillMessageBox();
             //停止Timer
             ((Timer)sender).Stop();
         } 

         private void KillMessageBox()
         {
             //按照MessageBox的标题，找到MessageBox的窗口
             IntPtr ptr = FindWindow(null, "MessageBox");
             if (ptr != IntPtr.Zero)
             {
                 //找到则关闭MessageBox窗口
                 PostMessage(ptr, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
             }
         }
     }
 }