A TextBox Which Accept Only String in C#

public form()

{
    initializeComponent();

    textbox.text.keypress + = new keypressEventHandler(text.box_keypress);

}

 Now drag and down a textbox and click on "Keypress event" 

private void textbox_keypress(obj sender, event e)

{
    char pressedkey = e.keychar;

    if(char.IsLetter(pressedkey)||char.IsSeparator(PressedKey)||char.IsPunction(pressedKey))

    {

        e.handled = false;

    }

    else

    e.handled = true;