如何用C#开发的计算器小软件

            TextBox a = new TextBox();//值1
            TextBox b = new TextBox();//值2
            TextBox c = new TextBox();//结果
            Button 计算 = new Button();
            DomainUpDown 符号 = new DomainUpDown();
            //添加到初始化事件里，下面的在初始化区域里
            a.Show();
            b.Show();
            c.Show();
            计算.Show();
            符号.Show();
           符号.Items.Add(new string[4] { "+", "-", "*", "/" });
            decimal aa;
            decimal bb;
            try
            {
                aa = decimal.Parse(a.Text);
                bb = decimal.Parse(b.Text);
            }
            catch
            {
                MessageBox.Show("输入不正确或数据过大");
                return;
            }
            //添加一个click事件，下面这些在click事件里
            switch (符号.Text)
            {
                case "+":
                    c.Text = (aa + bb).ToString();
                    break;
                case "-":
                    c.Text = (aa - bb) + "";
                    break;
                case "*":
                    c.Text = (aa * bb).ToString();
                    break;
                case "/":
                    try
                    {
                        c.Text = (aa / bb) + "";
                    }
                    catch (DivideByZeroException)//试图除以0
                    {
                        c.Text = "错误";
                    }
                    break;
            }
            //够详细了吧？求采纳

看入门教程，看完就会了