3. static method

[ITHelpself]

using System;
using System.ComponentModel.DataAnnotations;

namespace ConsoleApp1
{
    class Program
    { 
        static int tong(int a,int b)
        {
            return a + b;
        }
        static void inTong(int a, int b)
        {
            int c = tong(a, b);
            Console.WriteLine("tong a va b: " + c);
        }
        static void Main(string[] args)
        {
            int a = 5, b =8;
            inTong(a,b);

        }
    }
}

[ITHelpself]

using System;
using System.ComponentModel.DataAnnotations;

namespace ConsoleApp1
{
    class Program
    { 
        static double tong(double a,double b)
        {
            return a + b;
        }
        static void inTong(double a,double b)
        {
            double c = tong(a, b);
            Console.WriteLine("tong a va b: " + c);
        }
        static void Main(string[] args)
        {
            double a = 57, b = 8.5;
            inTong(a,b);

        }
    }
}

[nhokhacam1]

double: 3.5,-2.1,0.1,2,1,3,6

[ITHelpself]

 static double thuong(int a, int b)
        {
            return (double)a / b;
        }

[ITHelpself]

ép kiểu

[ITHelpself]

using System;
using System.ComponentModel.DataAnnotations;

namespace ConsoleApp1
{
    class Program
    { 
        static double tong(double a,double b)
        {
            return a + b;
        }
        static double thuong(int a, int b)
        {
            return (double)a / b;
        }
        static void inThuong(int a,int b)
        {
            double d = thuong(a, b);
            Console.WriteLine("thuong a va b: " + d);
        }
        static void inTong(double a,double b)
        {
            double c = tong(a, b);
            Console.WriteLine("tong a va b: " + c);
        }
        static void Main(string[] args)
        {
            double a = 5, b = 8.5;
            inTong(a,b);
           inThuong((int)a, (int)b);

        }
    }
}

[Duynguyen1819]

using System;
using System.Security.Cryptography;

namespace ConsoleApp1
{
    class Program
    {
        static double tinhTong(double a, double b)
        {
            return a + b;
        }
        static double tinhHieu(double a, double b)
        {
            return a - b;
        }
        static double tinhTich(double a, double b)
        {
            return a * b;
        }
        static double tinhThuong(double a, double b)
        {
            return a / b;
        }
        static void menu()
        {
            int luachon;
            double a, b;
            Console.Write("a:");
            a = double.Parse(Console.ReadLine());
            Console.Write("b:");
            b = double.Parse(Console.ReadLine());

            Console.WriteLine("------------menu-----------");
            Console.WriteLine("1 tong");
            Console.WriteLine("2 hieu");
            Console.WriteLine("3 tich");
            Console.WriteLine("4 thuong");
            // nhap lua chon
            luachon = int.Parse(Console.ReadLine());
            switch (luachon)
            {
                case 1:
                    //TODO: tong
                    double tong = tinhTong(a, b);
                    Console.WriteLine("tong = {0}",tong);
                    break;
                case 2:
                    //TODO: hieu
                    double hieu = tinhHieu(a, b);
                    Console.WriteLine("hieu = {0}",hieu);
                    break;
                case 3:
                    //TODO: tich
                    double tich = tinhTich(a, b);
                    Console.WriteLine("tich = {0}",tich);
                    break;
                case 4:
                    //TODO: thuong
                    double thuong = tinhThuong(a, b);
                    Console.WriteLine("thuong = {0}",thuong);
                    break;
            }
        }
        static void Main(string[] args)
        {
            menu();

        }
    }
}