How do I use PostMessageA in C#?

Question

I need to simulate keys in an minimized application so I guess PostMessageA would help me but how do I use it n C#?

Leeroy Fincher · Answer

I don't think I have the best of luck for your service

Sergio Fonseca · Answer

Thank you once again :-) Now I just need get to work the bypass of PostMessageA. I guess I gotta make the program in C++.

Alan · Answer

To move the mouse to the point x, y in the window (client, not screen coordinates) , I'd try this: const uint WM_MOUSEMOVE = 0x0200; PostMessage(hWnd, WM_MOUSEMOVE, 0, y * 0x10000 + x);

Sergio Fonseca · Answer

Thank you was exactly what I needed xP Also I'm not in need of Control or Shift but can I emulate mouse move?

Alan · Answer

Sorry Sergio. I hadn't noticed that you'd asked a supplementary on this until I linked to this thread from another forum where someone else was asking a similar question. If you haven't figured it out already then, to send backspace or left arrow, you need to know the virtual keycodes for those particular keys: const int VK_BACK = 0x08; const int VK_LEFT = 0x25; PostMessage(hWnd, WM_KEYDOWN, VK_BACK,0); PostMessage(hWnd, WM_KEYDOWN, VK_LEFT,0); There's a list of virtual key codes here: http://msdn2.microsoft.com/en-us/library/ms645540(VS.85).aspx Mostly, they work as above. However, to send Alt + Letter, I've found this works: const uint WM_SYSKEYDOWN = 0x104; // send Alt + F PostMessage(hWnd, WM_SYSKEYDOWN, VkKeyScan('F'), 1 However, I haven't been able to figure out how to send SHIFT or CONTROL plus something - everything I've tried hasn't worked :(

Sergio Fonseca · Answer

Thank you Alan worked fine :-) also how do I send special keys such as Backspace Left arrow and all those.

Alan · Answer

Here's a sample app I've just written. I first created an untitled Notepad window and minimized it: using System; using System.Diagnostics; using System.Runtime.InteropServices; class Program { [DllImport("user32.dll", SetLastError = true)] static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow); [DllImport("User32.Dll", EntryPoint = "PostMessageA")] static extern bool PostMessage(IntPtr hWnd, uint msg, int wParam, int lParam); [DllImport("user32.dll")] static extern byte VkKeyScan(char ch); const uint WM_KEYDOWN = 0x100; static void Main() { Process[] procs = Process.GetProcessesByName("Notepad"); foreach(Process proc in procs) { // look for untitled notepad window if(proc.MainWindowTitle == "Untitled - Notepad") { // get handle to Notepad's edit window IntPtr hWnd = FindWindowEx(proc.MainWindowHandle, IntPtr.Zero, "edit", null); // post "hello" to notepad string s = "hello"; for (int i = 0; i { PostMessage(hWnd, WM_KEYDOWN, VkKeyScan(s[i]), 0); } break; } } } }

How do I use PostMessageA in C#?

Answers (7)