How to make TextBox to receive only number key values using KeyDown Event in C#?

Question

This code in my form updates the textBox1.Text twice whenever number keys are pressed.

private void textBox1_KeyDown( object sender, KeyEventArgs e )          


        

Answer 1

When you press a key, a character is already appended to your TextBox. Then you run the following code and, if the key represents a number, you append it again:

if (char.IsNumber((char)e.KeyCode)) {
    textBox1.Text += (char)e.KeyCode;
}

If you want to suppress any key that's not a number, you could use this instead:

e.SuppressKeyPress = !char.IsNumber((char)e.KeyCode);