c#几个小程序怎么写？

//第一题： using System; class nums { static void Main(string[] args) { double num1, num2, num3; num1 = double.Parse(Console.ReadLine()); num2 = double.Parse(Console.ReadLine()); num3 = double.Parse(Console.ReadLine()); Console.WriteLine("三个数从大到小的顺序是："); if (num1 > num2) { if (num1 > num3) { if (num3 > num2) Console.WriteLine(num1 + " " + num3 + " " + num2); else Console.WriteLine(num1 + " " + num2 + " " + num3); } else Console.WriteLine(num3 + " " + num1 + " " + num2); } else { if (num1 > num3) Console.WriteLine(num2 + " " + num1 + " " + num3); else { if (num2 > num3) Console.WriteLine(num2 + " " + num3 + " " + num1); else Console.WriteLine(num3 + " " + num2 + " " + num1); } } } } //第二题： using System; class function { static void Main(string[] args) { double x, y; Console.WriteLine("请输入x的值"); x = double.Parse(Console.ReadLine()); if (x < 0) y = -1; else if (x == 0) y = 0; else y = 1; Console.WriteLine("y的值是" + y); } } //第三题： using System; class months { static void Main(string[] args) { int month; Console.WriteLine("请输入月数"); month = int.Parse(Console.ReadLine()); switch (month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: Console.WriteLine("这个月有31天！"); break; case 4: case 6: case 9: case 11: Console.WriteLine("这个月有30天！"); break; case 2: Console.WriteLine("这个月有28或29天！"); break; default: Console.WriteLine("您的输入有误！"); break; } } }