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C# Querying With LINQ Functional Programming in C# Lambda Expressions

Derek Etnyre
Derek Etnyre
20,822 Points

Difficult time thinking through the refactoring process

Having difficult time thinking through refactoring this line:

public Action<int, Func<int, int>> DisplayResult = delegate (int result, Func<int, int> function)

My first attempt was to put it like this:

public Func<int, Func<int, int>> DisplayResult = (int result, Func<int, int> function) =>

but keep thinking the two Func<int, int> 's can be simplified to something like this:

public Func<int, int> DisplayResult = (int result, int function) =>

Neither one is right - think my first attempt is closer to the solution.

Any suggestions on how to think through the refactoring process on this one?

Program.cs
using System;

namespace Treehouse.CodeChallenges
{
    public class Program
    {     
        public Func<int, int> Square = (int number) =>
        {
            return number * number;
        };

        public Func<int, int> DisplayResult = (int result, int function) =>
        {
            Console.WriteLine(function(result));
        };

        static void Main(string[] args)
        {

        }
    }
}

2 Answers

Steven Parker
Steven Parker
230,230 Points

:point_right: You almost got it on the 2nd attempt.

You just forgot that argument types for lambda's are inferred, not specified. Also, don't change the type of DisplayResult:

        public Action<int, Func<int, int>> DisplayResult = (result, function) =>

Oddly, it apparently let you get away with it on task 1.

Actually, you can compact things even more by eliminating the blocks (and the return on task 1:

        public Func<int, int> Square = number => number * number;

        public Action<int, Func<int, int>> DisplayResult = (result, function) =>
                Console.WriteLine(function(result));
Derek Etnyre
Derek Etnyre
20,822 Points

Thanks. Still something off that I'm not getting.

Have code looking like this now:

    public Func<int, int> displayResult = (result, function) =>
     {
         Console.WriteLine(function(result));
     };

but still not able to compile.

Put code into Visual Studio and it tells me: 'Delegate 'Func <int, int>' does not take 2 arguments.

Tells me I'm not fully understaning the Lambdas....

Derek Etnyre
Derek Etnyre
20,822 Points

Just figured it out - should have left the Func <int, int> in place - like this:

    public Action<int, Func<int, int>> DisplayResult = (result, function) =>
    {
        Console.WriteLine(function(result));
    };