Explanation for delgation and lamda expression.

DelgationHistory.cs

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

namespace DelegatesTest
{
    class Program
    {
        private delegate int SumPro(int f, int s);//=> Func<int f,int s, int r>
        private delegate int incre(int s); //=> Func<int x,int r>
        private delegate void prnt(int s); //=> Action<int x>
        static void Main(string[] args)
        {
            //normal delegation
            //with return type
            SumPro delMethd = new SumPro(Sumition);
            var result = delMethd(4, 5);
            Console.WriteLine(result);
            //no return
            prnt delprntMethod = new prnt(log);
            delprntMethod(455);


            //anonys delegation
            //with return type
            SumPro anonyDelMethod = delegate (int x, int y) { return x + y; };
            var result2 = anonyDelMethod(7, 3);
            Console.WriteLine(result2);
            //no return
            prnt annonyprntMehod = delegate (int x) { Console.WriteLine(x); };
            annonyprntMehod(477);



            //lambda non pro way [easy expression instead of delegate]
            //with return type
            SumPro lmdaNonMethod = (p, j) => { return p + j; };
            var result3 = lmdaNonMethod(6, 1);
            Console.WriteLine(result3);
            //non return
            prnt lmdaNonprintMethod = (p) => { Console.WriteLine(p); };
            lmdaNonprintMethod(88);

            //lambda pro way [params only one and body only return or samll code]
            //with return type
            incre lmdaMethod = p => p+8;
            // non return
            prnt lmdaprntmethod = p => Console.WriteLine(p);

            //--------------------------------------using predifined delgate [Action and Func]---------------
            //Action to do more code without specifying a return [like non pro lmda but no return] <in,in,....,in>
            Action<int> myAction = (x) => { var y = x + 1; Console.WriteLine(x++); };
            myAction.Invoke(455000);
          
            //Fun like Action but can return last args <in,in,...,out>
            Func<int, int, int> myFunSum = (f, s) => s + f;
            var resFun  = myFunSum(4, 44);



            //------------test on passing func

            //return student name length that matches it's order in the list
          
            var students = new List<string> { "Ahemd" , "Sara" , "ezz" , "Mohamed", "Sameh" , "Heba" };
            var results = students.FindMyItemTextThatMatchOrderOfIt(student =>student.Length);


            var postalcodes = new List<int> { 222,1158,20332,477,25608,2566,1470 };
            var results2 = postalcodes.FindMyItemTextThatMatchOrderOfIt(code => code.ToString().Length);


            Console.ReadLine();
        }

        private static int Sumition(int a,int b)
        {
            return a + b;
        }
        private static void log(int x)
        {
            Console.WriteLine(x);
        }

      
    }

    public static class Helpers
    {

        public static List<int> FindMyItemTextThatMatchOrderOfIt<T>(this List<T> studenMenu,Func<T,int> finder)
        {
            var results = new List<int>();
            for (int z = 0; z < studenMenu.Count; z++)
            {
                if (finder(studenMenu[z]) == z+1)
                    results.Add(z+1);

                
            }

            return results;
        }

    }
}