How to send continuous keypress to a program?

Question

I have been using SendKeys.Send() & SendKeys.SendWait() to send keys to the foreground program (a program different from the application written).

I tried sending a continuous key-press by sending repeatedly the same key with a certain delay between them but the effect was not the same as a continuous keypress in that application.

My question is: How can I send a continuous key-press to a program? The effect of that keypress must be the same as pressing myself that key continuously in the application.

SOLUTION EDIT

The solution was to call the method:

[DllImport("User32.dll")]
static extern int SendMessage(IntPtr hWnd, uint wMsg, UIntPtr wParam, IntPtr lParam);

with the parameters obtained from:

public System.Diagnostics.Process[] p = System.Diagnostics.Process.GetProcessesByName("process");

p[0].MainWindowHandle is hWnd

and using Spy on the window:

right clicking on a message line in Spy shows the wMsg, wParam and lParam (all 3 in hexadecimal)

SendMessage(p[0].MainWindowHandle, (uint)0x0100, (UIntPtr)0x00000041, (IntPtr)(0x001E0001));

By sending only one WM_KEYDOWN message the effect is as the key is pressed continuously. To stop the program acting as the key is continuously pressed i have to press that key on the keyboard and release it, so that WM_KEYUP is generated. Sending WM_KEYUP in the code gives an System.OverFlow "Arithmetic operation resulted in an overflow." exception. Any ideea why that might happen?

Thanks for your replies: Ation and takrl

Why do you need to do this? Maybe it would help if you explain what this is needed for. — takrl
Why did someone vote to close? "How do you send a continuous keypress" is a perfectly acceptable question. — user47589
@takrl: i wrote a program that sends commands to a game based on speech recognition and now i wanted to add a vocal command to walk forward, but repeatedly sending keys doesn't work. and that is why i want to send a continuous keypress — Răzvan Flavius Panda
@Inuyasha: thanks for the support (Shippo agrees to i think) :) i really don't get why someone would want to close a useful question that hasn't been answered here before — Răzvan Flavius Panda
@Inu I guess it was being voted to close since it wasn't clear what exactly @Răzvan was trying to do. I think his comment made that a bit more clear (see my answer), unless I misunderstood it ... — takrl

Ation Ation · Accepted Answer · 2011-07-11T10:03:42

Try to use Win API SendMessage with WM_KEYDOWN and WM_KEYUP. Proper delay should be between this messaging. Also you could use PostMessage for async sending.

[DllImport("User32.dll")]
            public static extern int SendMessage(IntPtr hWnd, uint msg, int wparam, int lparam);

How to send continuous keypress to a program?

2 Answers