Getting a list of Key pressed

Kenneth Haugland

I need to know the key that is currently pressed in a C# WPF application, so:

    List PressedKeys = new List();

    private void Window\_KeyDown(object sender, KeyEventArgs e)
    {
        //If key is pressed this stop resending
        if (!PressedKeys.Contains(e.Key))
        {
            PressedKeys.Add(e.Key);
            txtKeysDown.Text = String.Join(", ", PressedKeys);
        }
        
    }

    private void Window\_KeyUp(object sender, KeyEventArgs e)
    {
        PressedKeys.Remove(e.Key);
        txtKeysDown.Text = String.Join(", ", PressedKeys);
    }

This works, sort of. However, it does not give me the raw input from the keyboard so when AltGr is pressed it canges from Key.RightAlt => Key.LeftCtrl + Key.RightAlt whitch is Windows interpretation according to this: AltGr key - Wikipedia[^]. I dont want this, as I want the user to be able to "bind" any key to a spesific action. So I tried to use the user32.dll call:

[DllImport("user32.dll", EntryPoint = "GetKeyboardState", SetLastError = true)]
private static extern bool NativeGetKeyboardState([Out] byte[] keyStates);

    private static bool GetKeyboardState(byte\[\] keyStates)
    {
        if (keyStates == null)
            throw new ArgumentNullException("keyState");
        if (keyStates.Length != 256)
            throw new ArgumentException("The buffer must be 256 bytes long.", "keyState");
        return NativeGetKeyboardState(keyStates);
    }

    private static byte\[\] GetKeyboardState()
    {
        byte\[\] keyStates = new byte\[256\];
        if (!GetKeyboardState(keyStates))
            throw new Win32Exception(Marshal.GetLastWin32Error());
        return keyStates;
    }

    private static bool AnyKeyPressed()
    {
        byte\[\] keyState = GetKeyboardState();
        // skip the mouse buttons
        return keyState.Skip(8).Any(state => (state & 0x80) != 0);
    }
}

With the function:

    bool MyIsKeyDown(Key key)
    {

        return (((byte)GetKeyboardState()\[(int)key\] & 0x80) & 0x80)>0;
    }

and code implementation:

    private void Window\_KeyDown(object sender, KeyEventArgs e)
    {

        foreach (Key

Kenneth Haugland

Ok, I found a solution here: Using Raw Input from C# to handle multiple keyboards[^] However the WPF solution won't compile and apparently has a bug, but I found a git hub project that has a working WPF solution that I updated to VS2017 here: GitHub - aelij/RawInputProcessor: Provides a way to distinguish input from multiple keyboards[^] so problem solved.

Lost User

I've been using the "Keyboard" class to get the state of my keys; apparently without any issues. e.g.

bool ok = ( Keyboard.IsKeyDown( Key.LeftShift ) || Keyboard.IsKeyDown( Key.RightShift ) );

"(I) am amazed to see myself here rather than there ... now rather than then". ― Blaise Pascal

Kenneth Haugland

That could work, but I also want it to react to a sequence of inputs like Visual Studio does. For instance, if you have selected parts of the code you can hold LeftCtrl + K, release the keys and press LeftCtrl + F, VS will format the code for you. Then KeyBoard.IsDown is not really usable. The problem is that I need to know what happened on your keyboard before windows do changes to it.

Lost User

"Keyboard" is a "class"; "IsDown" is only one method; I didn't say to use it; it was an example. Anyway, what you're citing is a "sequence of key states" that translates into some operation; and has nothing to do with testing individual key states. Your problem is determining / tracking intent once a key is pressed.

"(I) am amazed to see myself here rather than there ... now rather than then". ― Blaise Pascal