四个数的运算

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

namespace sisisisiis
{
    class Program
    {
        private static int sun;
        private static int sum;
        private static int x, y, z,w;
        private static string f;
        private static string h;
        private static string j;
        static void Main(string[] args)
        {
            Console.Write("请输入随机数的范围(9-10)：");
            string azzz = Console.ReadLine();
            string regex = @"(d+)D+(d+)";
            Match mstr = Regex.Match(azzz, regex);
            int s1 = int.Parse(mstr.Groups[1].Value);
            int s2 = int.Parse(mstr.Groups[2].Value);
            random(s1, s2);
            Console.Write("请输入答案：");
            int l = int.Parse(Console.ReadLine());
            qlgs(f, x, y);
            hlgs(h, z, w);
            qlgs(j, sun, sum);
            if (l == sun)
            {
                Console.WriteLine("回答正确！");

            }
            else
            {
                Console.WriteLine("回答错误！");
            }
            Console.Read();
        }
        private static int qlgs(string a1,int a2,int a3)
        {
            switch (a1)
            {
                case "+":
                    sun = a2 + a3;
                    break;
                case "-":
                    sun = a2 - a3;
                    break;
                case "*":
                    sun = a2 * a3;
                    break;
                case "/":
                    if (a3 == 0)
                    {

                    }
                    else
                    {
                        sun = a2 / a3;
                    }
                    break;
            }
            return sun;
 
        }
        private static int hlgs(string b1, int b2, int b3)
        {
            switch(b1)
            {
                case "+":
                    sum = b2 + b3;
                    break;
                case "-":
                    sum = b2 - b3;
                    break;
                case "*":
                    sum = b2 * b3;
                    break;
                case "/":
                    if (b3 == 0)
                    {

                    }
                    else
                    {
                        sum = b2 / b3;
                    }
                    break;
            }
            return sum;
        }
        private static void random(int a,int b)
        {
            Random si = new Random();
            x = si.Next(a, b);
            y = si.Next(a, x);
            z = si.Next(a, y);
            w = si.Next(a, b);
            string[] operators = new string[] { "+", "-", "*", "/" };
            f = operators[new Random().Next(0, 4)];
            string[] opera = new string[] { "+", "-", "*", "/" };
            h = opera[new Random().Next(0, 4)];
            j = operators[new Random().Next(0, 4)];
            string z1 = "=";
            string xfyhz ="("+ x + f + y +")"+ h +"("+z +j+w+")"+ z1;
            Console.WriteLine(xfyhz);

        }
    }
}

总结：
总的来说这个方法很有局限性，没有把所有的情况都包括全，

  string[] operators = new string[] { "+", "-", "*", "/" };
            f = operators[new Random().Next(0, 4)];
            string[] opera = new string[] { "+", "-", "*", "/" };
            h = opera[new Random().Next(0, 4)];

为什么每次 f 都等于 h 不能这样用吗？

想了一下三个运算符，四个数，再加上是否带括号如果把所有的情况都列出来，有点不太可能，代码的重复性会更多。所以就用了这样的偷懒的方式！