How to get pressed char from System.Windows.Input.KeyEventArgs?

不羁岁月 提交于 2019-12-05 01:38:20
WPF-it

See this post... how to capture the '#' character on different locale keyboards in WPF/C#?

it has a utility function called GetCharFromKey(Key key) which gets locale specific character from the Key of the Keyboard event args.

Very useful.

Sometimes you just need to solved the problem with a sledgehammer.

char KeyToChar(Key key) {

    if (Keyboard.IsKeyDown(Key.LeftAlt)  ||
        Keyboard.IsKeyDown(Key.RightAlt) ||
        Keyboard.IsKeyDown(Key.LeftCtrl) ||
        Keyboard.IsKeyDown(Key.RightAlt))
    {
        return '\x00';
    }

    bool caplock  = Console.CapsLock;
    bool shift    = Keyboard.IsKeyDown(Key.LeftShift) || 
                            Keyboard.IsKeyDown(Key.RightShift);
    bool iscap    = (caplock && !shift) || (!caplock && shift);

        switch(key) {
            case Key.Enter:           return '\n';
            case Key.A:               return (iscap ? 'A' : 'a');
            case Key.B:               return (iscap ? 'B' : 'b');
            case Key.C:               return (iscap ? 'C' : 'c');
            case Key.D:               return (iscap ? 'D' : 'd');
            case Key.E:               return (iscap ? 'E' : 'e');
            case Key.F:               return (iscap ? 'F' : 'f');
            case Key.G:               return (iscap ? 'G' : 'g');
            case Key.H:               return (iscap ? 'H' : 'h');
            case Key.I:               return (iscap ? 'I' : 'i');
            case Key.J:               return (iscap ? 'J' : 'j');
            case Key.K:               return (iscap ? 'K' : 'k');
            case Key.L:               return (iscap ? 'L' : 'l');
            case Key.M:               return (iscap ? 'M' : 'm');
            case Key.N:               return (iscap ? 'N' : 'n');
            case Key.O:               return (iscap ? 'O' : 'o');
            case Key.P:               return (iscap ? 'P' : 'p');
            case Key.Q:               return (iscap ? 'Q' : 'q');
            case Key.R:               return (iscap ? 'R' : 'r');
            case Key.S:               return (iscap ? 'S' : 's');
            case Key.T:               return (iscap ? 'T' : 't');
            case Key.U:               return (iscap ? 'U' : 'u');
            case Key.V:               return (iscap ? 'V' : 'v');
            case Key.W:               return (iscap ? 'W' : 'w');
            case Key.X:               return (iscap ? 'X' : 'x');
            case Key.Y:               return (iscap ? 'Y' : 'y');
            case Key.Z:               return (iscap ? 'Z' : 'z');
            case Key.D0:              return (shift ? ')' : '0');
            case Key.D1:              return (shift ? '!' : '1');
            case Key.D2:              return (shift ? '@' : '2');
            case Key.D3:              return (shift ? '#' : '3');
            case Key.D4:              return (shift ? '$' : '4');
            case Key.D5:              return (shift ? '%' : '5');
            case Key.D6:              return (shift ? '^' : '6');
            case Key.D7:              return (shift ? '&' : '7');
            case Key.D8:              return (shift ? '*' : '8');
            case Key.D9:              return (shift ? '(' : '9');
            case Key.OemPlus:         return (shift ? '+' : '=');
            case Key.OemMinus:        return (shift ? '_' : '-');
            case Key.OemQuestion:     return (shift ? '?' : '/');
            case Key.OemComma:        return (shift ? '<' : ',');
            case Key.OemPeriod:       return (shift ? '>' : '.');
            case Key.OemOpenBrackets: return (shift ? '{' : '[');
            case Key.OemQuotes:       return (shift ? '"' : '\'');
            case Key.Oem1:            return (shift ? ':' : ';');
            case Key.Oem3:            return (shift ? '~' : '`');                   
            case Key.Oem5:            return (shift ? '|' : '\\');
            case Key.Oem6:            return (shift ? '}' : ']');
            case Key.Tab:             return '\t';
            case Key.Space:           return ' ';

            // Number Pad
            case Key.NumPad0:         return '0';
            case Key.NumPad1:         return '1';
            case Key.NumPad2:         return '2';
            case Key.NumPad3:         return '3';
            case Key.NumPad4:         return '4';
            case Key.NumPad5:         return '5';
            case Key.NumPad6:         return '6';
            case Key.NumPad7:         return '7';
            case Key.NumPad8:         return '8';
            case Key.NumPad9:         return '9';
            case Key.Subtract:        return '-';
            case Key.Add:             return '+';
            case Key.Decimal:         return '.';
            case Key.Divide:          return '/';
            case Key.Multiply:        return '*';

            default:                  return '\x00';
    }
}

Here's a more powerful version of the above code:

public struct IoCmd_t {
    public Key    key;
    public bool   printable;
    public char   character;
    public bool   shift;
    public bool   ctrl;
    public bool   alt;
    public int    type; //sideband
    public string s;    //sideband
};

public void KeyToChar(Key key, ref IoCmd_t KeyDecode) {
    bool iscap;
    bool caplock;
    bool shift;

    KeyDecode.key   = key;

    KeyDecode.alt   = Keyboard.IsKeyDown(Key.LeftAlt) || 
                      Keyboard.IsKeyDown(Key.RightAlt);

    KeyDecode.ctrl  = Keyboard.IsKeyDown(Key.LeftCtrl) ||
                      Keyboard.IsKeyDown(Key.RightCtrl);

    KeyDecode.shift = Keyboard.IsKeyDown(Key.LeftShift) ||
                      Keyboard.IsKeyDown(Key.RightShift);

    if (KeyDecode.alt || KeyDecode.ctrl) {
        KeyDecode.printable = false;                
        KeyDecode.type      = 1;                
    }
    else {
        KeyDecode.printable = true;
        KeyDecode.type      = 0;
    }

    shift    = KeyDecode.shift;
    caplock  = Console.CapsLock; //Keyboard.IsKeyToggled(Key.CapsLock);
    iscap    = (caplock && !shift) || (!caplock && shift);

    switch(key) {
        case Key.Enter:           KeyDecode.character = '\n'; return;
        case Key.A:               KeyDecode.character = (iscap ? 'A' : 'a');  return;
        case Key.B:               KeyDecode.character = (iscap ? 'B' : 'b');  return;
        case Key.C:               KeyDecode.character = (iscap ? 'C' : 'c');  return;
        case Key.D:               KeyDecode.character = (iscap ? 'D' : 'd');  return;
        case Key.E:               KeyDecode.character = (iscap ? 'E' : 'e');  return;
        case Key.F:               KeyDecode.character = (iscap ? 'F' : 'f');  return;
        case Key.G:               KeyDecode.character = (iscap ? 'G' : 'g');  return;
        case Key.H:               KeyDecode.character = (iscap ? 'H' : 'h');  return;
        case Key.I:               KeyDecode.character = (iscap ? 'I' : 'i');  return;
        case Key.J:               KeyDecode.character = (iscap ? 'J' : 'j');  return;
        case Key.K:               KeyDecode.character = (iscap ? 'K' : 'k');  return;
        case Key.L:               KeyDecode.character = (iscap ? 'L' : 'l');  return;
        case Key.M:               KeyDecode.character = (iscap ? 'M' : 'm');  return;
        case Key.N:               KeyDecode.character = (iscap ? 'N' : 'n');  return;
        case Key.O:               KeyDecode.character = (iscap ? 'O' : 'o');  return;
        case Key.P:               KeyDecode.character = (iscap ? 'P' : 'p');  return;
        case Key.Q:               KeyDecode.character = (iscap ? 'Q' : 'q');  return;
        case Key.R:               KeyDecode.character = (iscap ? 'R' : 'r');  return;
        case Key.S:               KeyDecode.character = (iscap ? 'S' : 's');  return;
        case Key.T:               KeyDecode.character = (iscap ? 'T' : 't');  return;
        case Key.U:               KeyDecode.character = (iscap ? 'U' : 'u');  return;
        case Key.V:               KeyDecode.character = (iscap ? 'V' : 'v');  return;
        case Key.W:               KeyDecode.character = (iscap ? 'W' : 'w');  return;
        case Key.X:               KeyDecode.character = (iscap ? 'X' : 'x');  return;
        case Key.Y:               KeyDecode.character = (iscap ? 'Y' : 'y');  return;
        case Key.Z:               KeyDecode.character = (iscap ? 'Z' : 'z');  return;
        case Key.D0:              KeyDecode.character = (shift ? ')' : '0');  return;
        case Key.D1:              KeyDecode.character = (shift ? '!' : '1');  return;
        case Key.D2:              KeyDecode.character = (shift ? '@' : '2');  return;
        case Key.D3:              KeyDecode.character = (shift ? '#' : '3');  return;
        case Key.D4:              KeyDecode.character = (shift ? '$' : '4');  return;
        case Key.D5:              KeyDecode.character = (shift ? '%' : '5');  return;
        case Key.D6:              KeyDecode.character = (shift ? '^' : '6');  return;
        case Key.D7:              KeyDecode.character = (shift ? '&' : '7');  return;
        case Key.D8:              KeyDecode.character = (shift ? '*' : '8');  return;
        case Key.D9:              KeyDecode.character = (shift ? '(' : '9');  return;
        case Key.OemPlus:         KeyDecode.character = (shift ? '+' : '=');  return;
        case Key.OemMinus:        KeyDecode.character = (shift ? '_' : '-');  return;
        case Key.OemQuestion:     KeyDecode.character = (shift ? '?' : '/');  return;
        case Key.OemComma:        KeyDecode.character = (shift ? '<' : ',');  return;
        case Key.OemPeriod:       KeyDecode.character = (shift ? '>' : '.');  return;
        case Key.OemOpenBrackets: KeyDecode.character = (shift ? '{' : '[');  return;
        case Key.OemQuotes:       KeyDecode.character = (shift ? '"' : '\''); return;
        case Key.Oem1:            KeyDecode.character = (shift ? ':' : ';');  return;
        case Key.Oem3:            KeyDecode.character = (shift ? '~' : '`');  return;
        case Key.Oem5:            KeyDecode.character = (shift ? '|' : '\\'); return;
        case Key.Oem6:            KeyDecode.character = (shift ? '}' : ']');  return;
        case Key.Tab:             KeyDecode.character = '\t'; return;
        case Key.Space:           KeyDecode.character = ' '; return;

        // Number Pad
        case Key.NumPad0:         KeyDecode.character = '0'; return;
        case Key.NumPad1:         KeyDecode.character = '1'; return;
        case Key.NumPad2:         KeyDecode.character = '2'; return;
        case Key.NumPad3:         KeyDecode.character = '3'; return;
        case Key.NumPad4:         KeyDecode.character = '4'; return;
        case Key.NumPad5:         KeyDecode.character = '5'; return;
        case Key.NumPad6:         KeyDecode.character = '6'; return;
        case Key.NumPad7:         KeyDecode.character = '7'; return;
        case Key.NumPad8:         KeyDecode.character = '8'; return;
        case Key.NumPad9:         KeyDecode.character = '9'; return;
        case Key.Subtract:        KeyDecode.character = '-'; return;
        case Key.Add:             KeyDecode.character = '+'; return;
        case Key.Decimal:         KeyDecode.character = '.'; return;
        case Key.Divide:          KeyDecode.character = '/'; return;
        case Key.Multiply:        KeyDecode.character = '*'; return;

        default:
            KeyDecode.type      = 1;
            KeyDecode.printable = false;
            KeyDecode.character = '\x00'; 
            return;
    } //switch          
} // function

You have e.Key property you can use for just that. Here's a link to msdn.

Edit:
I didn't realize you need the actual char. You can take a look here They say that in WPF you can do it using some Win32 APIs, while in Silverlight it seems rather difficult. Also you can look at KeyInterop.VirtualKeyFromKey - you can convert the WPF Key enum into a WinForms Keys enumeration, which does give you some more information. I haven't tried any of the solutions, so I don't know if any of them will work.
And one last thing. Why do you need the char from the KeyDown/Up event? Are you sure you can't use the TextChanged event instead? It will be much easier to get the exact char, if you can.

Here is a more modern approach:

private void Form1_KeyDown(object sender, KeyEventArgs e)
{
    var theKeyAsAString = e.KeyCode.ToString();
    var theKeyAsAChar = Convert.ToChar(theKeyAsAString);
}

You need to do that processing in the KeyPress event, not KeyDown or KeyUp. KeyEventArgs tell which actual key was pressed, not the corresponding character. Some of the keys don't event have an associated character. However KeyPressEventArgs will have an associated character because KeyPress event is not fired for characterless keys (ctrl, up, etc)

Phillip Kopprasch
char c = (char)e.KeyValue;

this will return the pressed key as a capital letter or a Number this will not work with special chars

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