c#屏幕抓图

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Drawing.Imaging;

namespace SaveScreenImage
{
    public partial class Form1 : Form
    {
        [DllImportAttribute("gdi32.dll")]
        private static extern bool BitBlt(
        IntPtr hdcDest, // 目标DC的句柄
        int nXDest,
        int nYDest,
        int nWidth,//宽度
        int nHeight,//高度
        IntPtr hdcSrc, // 源DC的句柄
        int nXSrc,
        int nYSrc,
        System.Int32 dwRop // 光栅的处理数值
        );
        public Form1()
        {
            InitializeComponent();