System;
using System.Windows.Forms;

namespace _05_08
{
public class Form_05_08 : Form
{
public Form_05_08()
{
this.Click += new EventHandler(this.Form_Click);
}

public void Form_Click(object sender, EventArgs e)
{
MessageBox.Show("您在窗体上单击了鼠标!");
}
}

public class Class_05_08
{
public static void Main(String[] args)
{
Application.Run(new Form_05_08());
}
}
这里的new eventhandler是什么类呢？？？怎么不见其定义呢？？