KeyDown event - how to easily know if the key pressed is numeric?

Question

I am currently handling the KeyDown event of a DataGridView control. One of the columns is filled by calculated values and I want the user to be able to override the cell va

Answer 1

Try

if ((e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9) ||
    (e.KeyCode >= Keys.NumPad0 && e.KeyCode <= Keys.NumPad9) ||
    e.KeyCode == Keys.Decimal)
{
    // Edit mode
}

Answer 2

void dataGridView1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
{
    // Used this to find they key values.
    //label1.Text += e.KeyValue;

    // Check if key is numeric value.
    if((e.KeyValue >= 48 && e.KeyValue <= 57) || (e.KeyValue >= 97 && e.KeyValue <= 105))
        System.Console.WriteLine("Pressed key is numeric");
}

Answer 3

Why use keycodes, when you can use this:

void Control_KeyPress(object sender, KeyPressEventArgs e)
    {

        if (Char.IsDigit(e.KeyChar))
        {
            //do something
        }
        else
        {
            //do something else
        }
    }

It's cleaner and even if microsoft decides to change all enums vlue, it still would work

Answer 4

If you use the KeyPress event, the event signature has a KeyPressEventArgs with a KeyChar member that gives you the character for the numberpad keys. You can do a TryParse on that to figure out if its a number or not.

private void Form1_KeyPress(object sender, KeyPressEventArgs e)
{
    int i;
    if (int.TryParse(e.KeyChar.ToString(), out i))
    {
        MessageBox.Show("Number");
    }
}

Answer 5

A bit more condensed version:

    private void KeyPress(object sender, KeyPressEventArgs e)
    {
        e.Handled = !Char.IsDigit(e.KeyChar); // only allow a user to enter numbers
    }

Answer 6

Sorcerer86pt's solution was the simplest, however, when a user presses a control key, like backspace, then it breaks. To solve that problem, you can use the following snippet:

void KeyPress(object sender, KeyPressEventArgs e)
{    
    if(!Char.IsNumber(e.KeyChar) && !Char.IsControl(e.KeyChar))
    {
        //The char is not a number or a control key
        //Handle the event so the key press is accepted
        e.Handled = true;
        //Get out of there - make it safe to add stuff after the if statement
        return;
    }
    //e.Handled remains false so the keypress is not accepted
}

If you're using WPF, you might find that a TextBox doesn't have a KeyPressed event. To fix this, I used the following code.

void ValidateKeyPress(object sender, KeyEventArgs e)
{
    char keyPressed = WPFUtils.Interop.Keyboard.GetCharFromKey(e.Key);
    if (!Char.IsNumber(keyPressed) && !Char.IsControl(keyPressed))
    {
        //As above
        e.Handled = true;
        return;
    }
}

You may notice the weird function call WPFUtils.Interop.Keyboard.GetCharFromKey(e.Key) this is one of the useful functions I've collected. You can find it here.