語言：C#  
功能：將畫面所有TextBox都清為空白


輸入畫面如上，使用者將剛才輸入項全部清空

        private void button1_Click(object sender, EventArgs e)
        {
            foreach (Control c in Controls)
            {
                if (c is TextBox)
                    c.Text = "";
            }