extension-methods-example.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Code4ItExamples.Extension_methods
{

    public static class ExtensionMethodExamples
    {
        public static void Do()
        {
            var person = new Person() { Name = "Davide", Surname = "Bellone", BirthDate = new DateTime(1990, 1, 1) };

            var student = new Student()
            {
                Name = "Elon",
                Surname = "Musk",
                BirthDate = new DateTime(1971, 6, 28),
                StudentId = 123
            };

            Console.WriteLine(student.GetFullNameWithBirthDate());
            Console.WriteLine(student.GetFullStudentInfo());

            Console.WriteLine(student.GetInitials());

            Console.ReadKey();

            List<int> myList = new List<int>() { 2, 4, 82, 6, 223, 5, 7, 342, 234, 1 };
            Console.WriteLine(myList.GetRandom());
            Console.WriteLine(myList.GetRandom());
            Console.WriteLine(myList.GetRandom());
            Console.WriteLine(myList.GetRandom());
        }
    }

    public class Person
    {
        public DateTime BirthDate { get; set; }
        public string Name { get; set; }
        public string Surname { get; set; }
        public string GetFullName() => $"{Surname} {Name}";
    }

    public class Student : Person
    {
        public int StudentId { get; set; }

    }

    public static class MyExtensions
    {

        public static string GetFullNameWithBirthDate(this Person person)
        {
            return $"{person.BirthDate.ToString("yyy-MM-dd")} - {person.GetFullName()}";
        }

        public static string GetFullStudentInfo(this Student student)
        {
            return $"{student.GetFullName()} - ID: {student.StudentId}";
        }

        public static string GetInitials(this Student student)
            => $"Student: {student.Surname.ToCharArray()[0]}.{student.Name.ToCharArray()[0]}.";

        public static string GetInitials(this Person person)
           => $"Person: {person.Surname.ToCharArray()[0]}.{person.Name.ToCharArray()[0]}.";


        public static T GetRandom<T>(this IEnumerable<T> source)
        {
            if (source == null || source.Count() == 0)
                throw new ArgumentException(nameof(source));
            Random rd = new Random();
            return source.ElementAt(rd.Next(0, source.Count()));
        }
    }

}