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C# Querying With LINQ Functional Programming in C# LINQ Method Syntax

Posted by Matt Thompson
Matt Thompson
23,413 Points

Step 2. Now, refactor the DisplayResult delegate to use a lambda expression?

I'm not understanding this step.

Current Go: 

    public Func<int, int> Square => delegate (int number)
    {
        return number * number;
    };

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

8 Answers

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

The challenge "check work" function seems to be broken.

Not here, but in step one. It should not have passed your refactoring of Square.

A correctly refactored Square would look more like this:

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

Notice that the equal sign (=) remains, but the term "delegate" does not. Also notice that the "goes to" symbols (=>) are placed between the argument and the returned value. Parentheses are not needed for a single argument, and braces are not needed for a return expression or a single statement.

Try using these guidelines for step 2, and/or review the video.

Also, you might want to report the challenge checker issue as a bug on the Support page.

micram1001
micram1001
33,833 Points
micram1001
micram1001
33,833 Points

For task two, remove all references to variables like ints, Func and the delegate too.

= (result, operation) =>

Dávid Polyovka
Dávid Polyovka
4,230 Points
Dávid Polyovka
Dávid Polyovka
4,230 Points

The solution is:

public Action<int, Func<int, int>> DisplayResult =  (result, function) =>
        {
            Console.WriteLine(function(result));
        };
Matt Thompson
Matt Thompson
23,413 Points
Matt Thompson
Matt Thompson
23,413 Points

Got it thanks!

Gil Wentzel
Gil Wentzel
22,932 Points
Gil Wentzel
Gil Wentzel
22,932 Points

I still cannot get the second task. Help please!

Stephanie Hallberg
Stephanie Hallberg
2,336 Points
Stephanie Hallberg
Stephanie Hallberg
2,336 Points

First task I did 

public Func<int, int> Square = (number) =>

and passed.

Second task I tried 

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

.. Nope.. Didn't work. And Considering the incredible short introduction to Lambda I dont think I can solve it.

Another question I have to bypass :/

Jake Steele
Jake Steele
6,098 Points

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

this should help

Jacob Clark
Jacob Clark
9,140 Points
Jacob Clark
Jacob Clark
9,140 Points 
public Func<int, int> Square = number => number * number;
public Action<int, Func<int, int>> DisplayResult = result, function) => Console.WriteLine(function(result));

Because I have a hell of a time myself with this, here's what worked for me.