C# sample code sharing for simulating PrintScreen and Alt+PrintScreen to capture screen pictures (picture)

C# Simulate PrintScreen and Alt+PrintScreen to capture screen pictures

keybd_event API

Function: This function synthesizes a keystroke event. The system can use this synthesized keystroke event to generate a WM_KEYUP or WM_KEYDOWN message, and the interrupt handler of the keyboard driver program calls the keybd_event function. In Windows NT this function has been replaced by SendInput.

Function prototype; VOID keybd_event (BYTE bVk, BYTE bScan, DWORD dwFlags, DWORD dwExtralnfo);

Parameters:

bVk: Define a Virtual key code. The key code value must be between 1 and 254.
bScan: Define the hardware scan code of this key.
　dwFlags:A set of flags that defines various aspects of the function's operation. The application can set the flag bits using a combination of some predefined constants as follows.
　KEYEVENTF_EXTENDEDKEY: If this value is specified, the previous value of the scan code is the prefix byte of OXEO (224).
KEYEVENTF_KEYUP: If this value is specified, the key will be released; if this value is not specified, the key will be pressed.
　dwExtralnfo: Defines additional 32-bit values ​​related to keystrokes.
Return value: This function has no return value.

Complete code:

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 PrintScreen
{
    public partial class Form1 : Form
    {

        [DllImport("user32.dll")]
        static extern void keybd_event
        (
            byte bVk,// 虚拟键值  
            byte bScan,// 硬件扫描码  
            uint dwFlags,// 动作标识  
            IntPtr dwExtraInfo// 与键盘动作关联的辅加信息  
        );

        /// <summary>
        /// 模拟Print Screen键盘消息，截取全屏图片。
        /// </summary>
        public void PrintScreen()
        {
            keybd_event((byte)0x2c, 0, 0x0, IntPtr.Zero);//down
            Application.DoEvents(); 
            keybd_event((byte)0x2c, 0, 0x2, IntPtr.Zero);//up
            Application.DoEvents(); 
        }

        /// <summary>
        /// 模拟Alt Print Screen键盘消息，截取当前窗口图片。
        /// </summary>
        public void AltPrintScreen()
        {
            keybd_event((byte)Keys.Menu, 0, 0x0, IntPtr.Zero);
            keybd_event((byte)0x2c, 0, 0x0, IntPtr.Zero);//down
            Application.DoEvents();
            Application.DoEvents();
            keybd_event((byte)0x2c, 0, 0x2, IntPtr.Zero);//up
            keybd_event((byte)Keys.Menu, 0, 0x2, IntPtr.Zero);
            Application.DoEvents();
            Application.DoEvents();
        } 

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        /// <summary>
        /// 从剪贴板获取图片
        /// </summary>
        /// <returns></returns>
        private Bitmap GetScreenImage()
        {
            IDataObject newobject = null;
            Bitmap NewBitmap = null;

            try
            {
                Application.DoEvents();
                newobject = Clipboard.GetDataObject();

                if (Clipboard.ContainsImage())
                {
                    NewBitmap = (Bitmap)(Clipboard.GetImage().Clone());
                }

                return NewBitmap;
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
                return null;
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            button1.Enabled = false;
            pictureBox1.Image = null;
            PrintScreen();
            pictureBox1.Image = GetScreenImage();
            button1.Enabled = true;
            Application.DoEvents();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            button2.Enabled = false;
            pictureBox1.Image = null;
            AltPrintScreen();
            pictureBox1.Image = GetScreenImage();
            button2.Enabled = true;
            Application.DoEvents();
        }

    }
}

Running effect:

Legacy issues:

No task issues with PrintScreen, but when using AltPrintScreen for the first time I can't always get the correct picture, I don't know why! I hope an expert can pass by and give me some advice. I’d be very grateful!

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