How Can I Reliably Send Keyboard Input to Another Application?

How to Send a Key to Another Application: An Enhanced Guide

Sending keys to other applications is a fundamental aspect of automation. While the provided code attempts to do this, it faces some challenges.

Issue:

The original code fails to send keys to Notepad because it does not properly activate the application. Setting the foreground window is crucial for keystrokes to be received by the desired program.

Solution:

To successfully send a key to Notepad, the code must first ensure that the application is active. This can be achieved using the SetForegroundWindow function with the MainWindowHandle of the target process. The enhanced code below demonstrates this:

// import SetForegroundWindow
[DllImport("User32.dll")]
static extern int SetForegroundWindow(IntPtr point);

private void SendKey()
{
    Process p = Process.GetProcessesByName("notepad").FirstOrDefault();
    if (p != null)
    {
        IntPtr h = p.MainWindowHandle;
        SetForegroundWindow(h);
        SendKeys.SendWait("k");
    }
}

Background Sending:

It is not possible to send keys to a background application without first activating it. The code provided does not support sending keys to background processes. If Notepad is not active, the keystrokes will be lost.

Non-Administrator Applications:

In cases where Notepad is running as Administrator and the sending application is not, the code may fail. This is because elevated processes have restricted access to non-elevated applications. To overcome this issue, the sending application must also run as Administrator.

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