Explain The C# Code

Question

using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

public static void Main()

{

	Console.WriteLine("Hello World");

	var nums = new List<NumberHolder> { new NumberHolder{ Val = 1 }, new NumberHolder{ Val = 2 }, new NumberHolder{ Val = 3 } };

	IEnumerable<NumberHolder> multiplyResult = nums.Select(i => Multiply(i)); 

	IEnumerable<NumberHolder> addOneResult = nums.Select(i => AddOne(i));

	

	foreach(var val in multiplyResult)

	{

		Console.WriteLine($"Multiply result : {val.Val}");

	}

	

	Console.WriteLine("------");

	

	foreach(var val in addOneResult)

	{

		Console.WriteLine($"Add one result : {val.Val}");

	}

}



static NumberHolder AddOne(NumberHolder numberHolder) 

{ 

	numberHolder.Val += 1; 

	return numberHolder; 

}



static NumberHolder Multiply(NumberHolder numberHolder)

{ 

	numberHolder.Val = numberHolder.Val * numberHolder.Val;

	return numberHolder;

}

}

class NumberHolder

{

public int Val { get; set; }

}

Answer 1

to read this code you need to understand delegate callbacks:

https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/delegates/

and linq:

https://learn.microsoft.com/en-us/dotnet/standard/linq/

and lambda expressions:

https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/lambda-expressions

note: the code:

IEnumerable<NumberHolder> multiplyResult = nums.Select(i => Multiply(i)); IEnumerable<NumberHolder> addOneResult = nums.Select(i => AddOne(i));

can be simplified to:

var multiplyResult = nums.Select(Multiply)
var addOneResult = nums.Select(AddOne);