CheckBox的基本用法

protected void Button1_Click(object sender, EventArgs e)
   {
       float aa = Convert.ToSingle(TextBox1.Text);
       float bb = Convert.ToSingle(TextBox2.Text);
       if (CheckBox1.Checked)
       {
           float cc = (aa + bb) * (float)0.7;
           TextBox3.Text = cc.ToString();

       }
       else
       {
           float dd = aa + bb;
           TextBox3.Text = dd.ToString();
       }
   }