textbox should accept only characters

1. write the code below at keypress event of textbox

private void txtFirstname_KeyPress(object sender, KeyPressEventArgs e)

        {

            if ((e.KeyChar >= 65 && e.KeyChar <= 90) || (e.KeyChar >= 97 && e.KeyChar <= 122) || (e.KeyChar == 32) || (e.KeyChar == 8))//keychar 8 is for backspace

            {

                e.Handled = false;

            }

            else

            {

                e.Handled = true;

            }

        }

it should accept alphabets only.