C#:从Windows服务捕获屏幕

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

public class ScreenCaptureService : ServiceBase
{
    private Bitmap _bitmap;
    private Graphics _graphics;
    private IntPtr _hDC;
    private IntPtr _hDestDC;
    private IntPtr _hBitmap;
    private IntPtr _hOldBitmap;

    public ScreenCaptureService()
    {
        InitializeComponent();
    }

    protected override void OnStart(string[] args)
    {
        _bitmap = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height, PixelFormat.Format32bppArgb);
        _graphics = Graphics.FromImage(_bitmap);
        _hDC = _graphics.GetHdc();
        _hDestDC = CreateCompatibleDC(_hDC);
        _hBitmap = _bitmap.GetHbitmap();
        _hOldBitmap = SelectObject(_hDestDC, _hBitmap);
        BitBlt(_hDestDC, 0, 0, _bitmap.Width, _bitmap.Height, _hDC, 0, 0, TernaryRasterOperations.SRCCOPY);
        SelectObject(_hDestDC, _hOldBitmap);
        DeleteDC(_hDestDC);
        _graphics.ReleaseHdc(_hDC);
        _graphics.Dispose();
    }

    protected override void OnStop()
    {
        _bitmap.Dispose();
    }

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateCompatibleDC(IntPtr hDC);

    [DllImport("gdi32.dll")]
    private static extern bool DeleteDC(IntPtr hDC);

    [DllImport("gdi32.dll")]
    private static extern IntPtr SelectObject(IntPtr hDC, IntPtr hObject);

    [DllImport("gdi32.dll")]
    private static extern bool BitBlt(IntPtr hObject, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hObjSource, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);
}