用C#语言 帮帮忙 我明天要用  我是菜鸟 不会弄这个题目  请各位高手帮帮忙吧！

            switch(z)
            {
                case "+":
                y = x1 + x2;
                break;
                case "*":
                y = x1 * x2;
                break;
                case "-":
                y = x1 - x2;
                break;
                case "/":
                y = x1 / x2;
                break;
                default:
                   printf("运算符输入错误");
                    break;
            }
           print（y）；
大至思路是这样 语法我模糊了 如果你学习就知道怎么改 前面是声明变量 赋个初值