How to convert a character to key code?

Question

Hello everyone,

How can I convert backslash key ('\') to key code?

On my keyboard backslash code is 220, but the method below

(int)'\\'

returns me 92.

I need some generic conversion like

 int ConvertCharToKeyValue(char c)
 {
     // some code here...
 }

Any ideas?

Answer 1

It depends on the ASCII table you are using.

try the following code:

System.Text.ASCIIEncoding.ASCII.GetBytes(myString);

Answer 2

Have you seen this answer? http://stackoverflow.com/questions/318777/c-how-to-translate-virtual-keycode-to-char

Answer 3

There is not a function that I know of that will map a character to a virtual key code. However, you can use the following table to start building such a mapping.

http://msdn.microsoft.com/en-us/library/dd375731(v=VS.85).aspx.

Note that you will need to know the keyboard, looking at the key you mention '\' this is the VK_OEM_5 virtual key which for US keyboards is '\' if not shifted and '|' if shifted, so your function will need to know the keyboard being used as well.

Of course if you want to map from a virtual key code to a character you can use interop to call the MapVirtualKeyEx function.

Update Based on your comment this would give you what you want.

[DllImport("user32.dll")]
static extern int MapVirtualKey(int uCode, uint uMapType);

const uint MAPVK_VK_TO_CHAR = 0x02;

private void textBox1_KeyDown(object sender, KeyEventArgs e)
{
  int key = MapVirtualKey((int)e.KeyCode, MAPVK_VK_TO_CHAR);
  if (key == (int)'\\')
  {

  }
}

Answer 4

You can P/Invoke VkKeyScan() to convert a typing key code back to a virtual key. Beware that the modifier key state is important, getting "|" requires holding down the shift key on my keyboard layout. Your function signature doesn't allow for this so I just made something up:

    public static Keys ConvertCharToVirtualKey(char ch) {
        short vkey = VkKeyScan(ch);
        Keys retval = (Keys)(vkey & 0xff);
        int modifiers = vkey >> 8;
        if ((modifiers & 1) != 0) retval |= Keys.Shift;
        if ((modifiers & 2) != 0) retval |= Keys.Control;
        if ((modifiers & 4) != 0) retval |= Keys.Alt;
        return retval;
    }

    [System.Runtime.InteropServices.DllImport("user32.dll")]
    private static extern short VkKeyScan(char ch);

Also beware of keyboard layouts that need to use dead keys (Alt+Gr) to generate typing keys. This kind of code is really best avoided.

Answer 5

If

var char = System.Windows.Forms.Keys.OemPipe; // 220
var code = (int)char;

then

public static int ToKeyValue(this char ch)
{
    return (int)(System.Windows.Forms.Keys)ch;
}