我的代码从第一个屏幕获取截图如下所示：

private void btnScreenOne_Click(object sender,EventArgs e) 
 {
     Bitmap bitmap = new Bitmap(Screen.PrimaryScreen.Bounds.Width,Screen.PrimaryScreen.Bounds.Height);

     Graphics graphics = Graphics.FromImage(bitmap as Image);

     graphics.CopyFromScreen(0,bitmap.Size);

     bitmap.Save(@"C:\Users\kraqr\Documents\PrintScreens\" + 
        DateTime.Now.ToString("yyyy-MM-dd_HH-mm-ss") + " Screen1" + 
        ".bmp",ImageFormat.Bmp);

}

感谢答案.