Ndtyjky

I'm trying to show informations on the Keyboard Keys pressed.

This code displays the Uppercase letters correctly, but the Uppercase information is shown also when a lowercase letter is pressed.

How can I solve this problem?
Here is what I am trying to do:

public partial class keyDemo : Form

{

    private void keyDemo_KeyPress(object sender, KeyPressEventArgs e)

    {

        charLabel.Text = $"Key pressed: {e.KeyChar}";

    }



    private void keyDemo_KeyDown(object sender, KeyEventArgs e)

    {

        keyInfoLabel.Text =

            $"Alt: {(e.Alt ? "Yes" : "No")}n" +

            $"Shift: {(e.Shift ? "Yes" : "No")}n" +

            $"Ctrl: {(e.Control ? "Yes" : "No")}n" +

            $"KeyCode: {e.KeyCode}n" +

            $"KeyData: {e.KeyData}n" +

            $"KeyValue: {e.KeyValue}";

    }



    private void keyDemo_KeyUp(object sender, KeyEventArgs e)

    {

        charLabel.Text = "";

        keyInfoLabel.Text = "";

    }

}

The reason for this is that KeyEventArgs returns details of a key, not a character. (The capital and lowercase letters use the same key.)
Some keys don't produce characters (e.g. Shift, F-keys), some produce non-printable characters (e.g. Tab, Escape) and the character produced by a certain keystroke depends on on your keyboard layout.

If you want the character, you should probably be using the KeyPress rather than KeyDown event.

But if you want to do it:

As @PrinceOfRavens says, you'd have to check the state of the Caps Lock key.

You can do it like this, but this still doesn't handle keys other than letters, and doesn't handle Alt Gr (for accented letters). To fully convert a keystroke to a character, you'd have to convert both Keys.Add (numeric keypad '+') and Shift '=' on most keyboards to "+", and Shift '1' usually to "!" (depending on your keyboard layout).

You could extend it by replacing the return null in KeyToLetter, but this is NOT the recommended way to get a character typed.

(I've added two items to the output.)

    using System.Runtime.InteropServices;   // for GetKeyState



    ...





    private void keyDemo_KeyDown(object sender, KeyEventArgs e)

    {

        keyInfoLabel.Text =

            $"Alt: {(e.Alt ? "Yes" : "No")}n" +

            $"Shift: {(e.Shift ? "Yes" : "No")}n" +

            $"Ctrl: {(e.Control ? "Yes" : "No")}n" +

            $"KeyCode: {e.KeyCode}n" +

            $"KeyData: {e.KeyData}n" +

            $"KeyValue: {e.KeyValue}n" +

            $"CapsLock: {(CapsLockState ? "Yes" : "No")}n" +

            $"Letter: {KeyToLetter(e.KeyData, CapsLockState)}";

    }



    // Import the DLL to use a Win32 API call.

    // See https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-getkeystate

    // If using WPF, you could use Keyboard.IsKeyDown :

    //  https://docs.microsoft.com/en-us/dotnet/api/system.windows.input.keyboard.iskeydown?view=netframework-4.7.2

    [DllImport("user32.dll")]

    public static extern short GetKeyState(Keys nVirtKey);



    /// <summary>

    /// true if Caps Lock is on, otherwise false.

    /// </summary>

    public bool CapsLockState 

        => (GetKeyState(Keys.CapsLock) & 1) == 1;



    /// <summary/>

    /// <param name="key">A base key (no modifiers).</param>

    /// <returns>true if and only if the given key represents a letter.</returns>

    public static bool IsLetterKey(Keys key)

        => key >= Keys.A && key <= Keys.Z;



    /// <summary>

    /// Given a keystroke that produces a letter, this returns the letter.

    /// </summary>

    /// <param name="key"></param>

    /// <param name="capsLockState"></param>

    /// <returns>the letter, or null if the given keystroke does not produce a letter.</returns>

    public static char? KeyToLetter(Keys key, bool capsLockState)

    {

        Keys baseKey = key & ~Keys.Modifiers;  // remove modifier keys

        if (IsLetterKey(baseKey) && !key.HasFlag(Keys.Control))    // if a letter

        {

            bool shiftPressed = key.HasFlag(Keys.Shift);   // check whether Shift was pressed

            bool capital = capsLockState ^ shiftPressed;   // if it should be capital

            if (capital)

                return (char)baseKey;

            else

                return Char.ToLower((char)baseKey);

        }

        else

        {

            return null;  // not a letter

        }

    }