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Hello, It's Isabel García from Barcelona and I am finding some problems with PostMessage method to send a mouse event to a web browser.

public void onClick2()
        Process[] notepads = Process.GetProcessesByName("chrome");
        if (notepads.Length == 0) return;
        if (notepads[0] != null)
            hWnd = FindWindowEx(notepads[0].MainWindowHandle, new IntPtr(0), "Edit", null);
            PostMessage(hWnd, MOUSEEVENTF_RIGHTDOWN, VK_RETURN, 0x001C0001);
            PostMessage(hWnd, MOUSEEVENTF_RIGHTDOWN, VK_DOWN, 0x00500001);



The button in which I have to click has a unique id:
<a href="#" id="action-button" title="Share on WhatsApp" class="button button--simple button--primary">Send</a>

And I would like to access to that id. Using Spy++ I am not able to access to that button.

What I have tried:

I have used SendKeys but it has worked with Notepad app.
I have used Spy++ but without success with chrome web page.
I have perfom a click doing the following:
private const uint MOUSEEVENTF_MOVE = 0x0001;
    private const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
    private const uint MOUSEEVENTF_LEFTUP = 0x0004;
    private const uint MOUSEEVENTF_RIGHTDOWN = 0x0008;
    private const uint MOUSEEVENTF_RIGHTUP = 0x0010;
    private const uint MOUSEEVENTF_ABSOLUTE = 0x8000;
public void performClick(uint x, uint y)
        //SetCursorPos(x, y);
        mouse_event(MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_LEFTDOWN, x, y, 0, UIntPtr.Zero);
        mouse_event(MOUSEEVENTF_ABSOLUTE | MOUSEEVENTF_LEFTUP, x, y, 0, UIntPtr.Zero);
        UnityEngine.Debug.Log("performClick x: " + x  + "y: "+ y);
        //PostMessage(handle, MOUSEEVENTF_LEFTDOWN, 5, 5);
Updated 13-May-19 2:44am
Gerry Schmitz 13-May-19 12:18pm    
Are you using the "Browser control"? If not why not? If you do, you can access the DOM.
Richard Deeming 14-May-19 12:01pm    
If you're trying to automate a web browser, why not use a tool that's specifically built to do that?
Selenium - Web Browser Automation[^]

Spy++ and PostMessage will only target controls which have their own window handle. Browsers don't create a separate window handle for every element on the page. If they did, the performance and memory usage would be horrendous.

1 solution

You probably need to make the window active first, see article here: Sending Keystrokes to another Application in C#[^]
Share this answer
Member 13615623 13-May-19 8:52am    
Hello! Thank you very much for the quick response. I have tried the following:
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 test
public partial class Form1 : Form
public Form1()

const int WM_KEYDOWN = 0x100;
const int WM_KEYUP = 0x101;
const int WM_SYSKEYDOWN = 0x104;
const int VK_BACK = 0x08;
const int VK_F5 = 116; //Ox74

public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

[DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

static extern byte VkKeyScan(char ch);

[DllImport("User32.Dll", EntryPoint = "PostMessageA")]
static extern bool PostMessage(IntPtr hWnd, uint msg, int wParam, int lParam);

private void Form1_Load(object sender, EventArgs e)


private void button1_Click_1(object sender, EventArgs e)
string msg = "123456";
IntPtr noteWnd = FindWindow("Notepad", null);
if (!noteWnd.Equals(IntPtr.Zero))
IntPtr editWnd = FindWindowEx(noteWnd, IntPtr.Zero, "Edit", null);
if (!editWnd.Equals(IntPtr.Zero))
for (int i = 0; i < msg.Length; i++)
PostMessage(editWnd, WM_KEYDOWN, VkKeyScan(msg[i]), 0);
PostMessage(editWnd, WM_KEYDOWN, VK_BACK, 0);
PostMessage(editWnd, WM_KEYDOWN, VK_BACK, 0);
//PostMessage(editWnd, WM_SYSKEYDOWN, VkKeyScan('F'), 1 << 29);
PostMessage(editWnd, WM_KEYDOWN, VK_F5, 0);
PostMessage(editWnd, WM_KEYUP, VK_F5, 0);
//PostMessage(editWnd, WM_KEYUP, VK_F, 0);
Member 13615623 13-May-19 9:09am    
It does work with notepad without focusing on the screen. However, I can not make it works with browser!

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