How do I make a textbox that only accepts numbers?

Handle the appropriate keyboard events to prevent anything but numeric input. I've had success with this two event handlers on a standard TextBox:

<?php
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)

{

    if (!char.IsControl(e.KeyChar) 

        && !char.IsDigit(e.KeyChar) 

        && e.KeyChar != '.')

    {

        e.Handled = true;

    }


    // only allow one decimal point

    if (e.KeyChar == '.' 

        && (sender as TextBox).Text.IndexOf('.') > -1)

    {

        e.Handled = true;

    }

}