Sending specific keys on the Numpad like +, -, / or Enter (simulating a keypress)

Question

I am working on a project where it is necessary to simulate key-presses to cause specific behaviours in a different application.

All is running well and fine, using

Answer 1

Since you are talking about a the-other-way-round solution, detecting the event, and I want to raise it, I don't even have to override the WndProc. I can simply send my own messages.

From your solution, I had a look at SendMessage/PostMessage, and then WM_KEYDOWN and WM_KEYUP. The documentation actually gives you the info (if you look really really hard).

http://msdn.microsoft.com/en-us/library/ms646280(v=vs.85).aspx
http://msdn.microsoft.com/en-us/library/ms646281(v=vs.85).aspx

So my solution (compiles and now with finding the right window (where to enter the text)) is like this:

 bool keyDown = true; // true = down, false = up
 const uint WM_KEYDOWN = 0x0100;
 const uint WM_KEYUP = 0x0101;
 const int VK_RETURN = 0x0D;

 IntPtr handle = IntPtr.Zero;
 // Obtain the handle of the foreground window (active window and focus window are only relative to our own thread!!)
 IntPtr foreGroundWindow = GetForegroundWindow();
 // now get process id of foreground window
 uint processID;
 uint threadID = GetWindowThreadProcessId(foreGroundWindow, out processID);
 if (processID != 0)
 {
 // now get element with (keyboard) focus from process
 GUITHREADINFO threadInfo = new GUITHREADINFO();
 threadInfo.cbSize = Marshal.SizeOf(threadInfo);
 GetGUIThreadInfo(threadID, out threadInfo);
 handle = (IntPtr)threadInfo.hwndFocus;
 }

 int lParam = 1 << 24; // this specifies NumPad key (extended key)
 lParam |= (keyDown) ? 0 : (1 << 30 | 1 << 31); // mark key as pressed if we use keyup message
 PostMessage(handle, (keyDown) ? WM_KEYDOWN : WM_KEYUP, VK_RETURN, lParam); // send enter

Hope it is useful to someone else as well. As was Vendetta's tip to me.

And.. if you do have a better solution, please say so!

Answer 2

I found this here works for me !

protected override void WndProc(ref Message m)
{
     if (m.Msg == 256 && m.WParam.ToInt32() == 13)
     {   // WM_KEYDOWN == 256, Enter == 13
         if ((m.LParam.ToInt32() >> 24) == 0)
         {
             MessageBox.Show("main enter pressed!");
         }
         else
         {
             MessageBox.Show("numpad enter pressed!");
         }
      }
      else
      {
         base.WndProc(ref m);
      }
}

Answer 3

thanks to andreas for providing the beginning of a solution. here's a more complete version:

[DllImport("user32.dll")]
private static extern IntPtr PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();
[DllImport("user32.dll")]
private static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);
[DllImport("user32.dll")]
private static extern bool GetGUIThreadInfo(uint idThread, out GUITHREADINFO lpgui);

public struct GUITHREADINFO
{
    public int cbSize;
    public int flags;
    public int hwndActive;
    public int hwndFocus;
    public int hwndCapture;
    public int hwndMenuOwner;
    public int hwndMoveSize;
    public int hwndCaret;
    public System.Drawing.Rectangle rcCaret;
}

private void sendNumpadEnter()
{
    bool keyDown = true; // true = down, false = up
    const uint WM_KEYDOWN = 0x0100;
    const uint WM_KEYUP = 0x0101;
    const int VK_RETURN = 0x0D;

    IntPtr handle = IntPtr.Zero;
    // Obtain the handle of the foreground window (active window and focus window are only relative to our own thread!!)
    IntPtr foreGroundWindow = GetForegroundWindow();
    // now get process id of foreground window
    uint processID;
    uint threadID = GetWindowThreadProcessId(foreGroundWindow, out processID);
    if (processID != 0)
    {
        // now get element with (keyboard) focus from process
        GUITHREADINFO threadInfo = new GUITHREADINFO();
        threadInfo.cbSize = Marshal.SizeOf(threadInfo);
        GetGUIThreadInfo(threadID, out threadInfo);
        handle = (IntPtr)threadInfo.hwndFocus;
    }

    int lParam = 1 << 24; // this specifies NumPad key (extended key)
    lParam |= (keyDown) ? 0 : (1 << 30 | 1 << 31); // mark key as pressed if we use keyup message

    PostMessage(handle, (keyDown) ? WM_KEYDOWN : WM_KEYUP, VK_RETURN, lParam); // send enter
}