这个小程序需要用到系统API，也就是需要用到user32中的三个函数。
第一个：WindowFromPoint 返回一个窗口句柄
第二个：GetWindowText  获取窗口标题
第三个：GetClassName  获取类名
当然，最重要的一点就是要引用命名空间：using System.Runtime.InteropServices;
先来看看做出来的效果：

在来看看源码：
------------------源码部分-------------------------
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 prjCursorHandler
{
    public partial class Form1 : Form
    {
        //获取窗口标题
        [DllImport("user32", SetLastError = true)]
        public static extern int GetWindowText(
        IntPtr hWnd, //窗口句柄
        StringBuilder lpString, //标题
        int nMaxCount  //最大值
        );
        //获取类的名字
        [DllImport("user32.dll")]
        private static extern int GetClassName(
            IntPtr hWnd, //句柄
            StringBuilder lpString, //类名
            int nMaxCount //最大值
        );
        //根据坐标获取窗口句柄
        [DllImport("user32")]
        private static extern IntPtr WindowFromPoint(
        Point Point  //坐标
        );
        public Form1()
        {
            InitializeComponent();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            this.timer1.Enabled = !this.timer1.Enabled;
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            int x = Cursor.Position.X;
            int y = Cursor.Position.Y;
            Point p = new Point(x, y);
            IntPtr formHandle = WindowFromPoint(p);//得到窗口句柄
            StringBuilder title = new StringBuilder(256);
            GetWindowText(formHandle, title, title.Capacity);//得到窗口的标题
            StringBuilder className = new StringBuilder(256);
            GetClassName(formHandle, className, className.Capacity);//得到窗口的句柄
            this.textBox1.Text = "窗口句柄:" + formHandle.ToString() + Environment.NewLine + "窗口标题:" + title + Environment.NewLine + "类名:" + className;
        }

        private void textBox1_KeyDown(object sender, KeyEventArgs e)
        {
            if(e.KeyCode==Keys.Enter || e.KeyCode==Keys.Space)
            {
                this.button1.PerformClick();
            }
        }
    }
}