using System; namespace Lesson05.Helpers { static class MathHelper { public static int Add(int a, int b) { return a + b; } public static int Multiply(int a, int b) { return a * b; } public static double Divide(int a, int b) { if (b == 0) { Console.WriteLine("除数不能为0!"); return 0; } return (double)a / b; } } }