类库的引用

还可以自己引用类库：解决方案-添加-新建项目

主程序

using System;
using System.Windows.Forms;
using Tools;

namespace ConsoleApp2
{
    class Program
    {
        static void Main(string[] args)
        {
            //Console.WriteLine("helloword");
            // Form form = new Form();
            // form.ShowDialog();
            double result = Calculator.Mul(3, 4);
            Console.WriteLine(result);
        }
    }
}

在引用里添加自己创建的类库

类库程序

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;



namespace Tools
{
    public class Calculator
    {
        public static double Add(double a, double b)
        {
            return a + b;
        }
        public static double Sub(double a, double b)
        {
            return a - b;
        }
        public static double Mul (double a, double b)
        {
            return a * b;
        }
        public static double Div(double a, double b)
        {
            if (b == 0)
            {
                return double.PositiveInfinity;
            }
            else
            {
                return a / b;
            }
        }

    }
}