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C# Querying With LINQ Query Operators Joins

Scott Tucker
Scott Tucker
3,765 Points

Joins Challenge help

When I used query syntax to solve this challenge I passed, but I want to be able to use and understand how to do this with method syntax. I have watched the video prior to this over and over again and I just can't seem to get it right. I believe that my resultSelector is wrong but I don't know exactly how to fix it.

CodeChallenge.cs
var myBirds = new List<Bird> 
{ 
    new Bird { Name = "Cardinal", Color = "Red", Sightings = 3 },
    new Bird { Name =  "Dove", Color = "White", Sightings = 2 },
    new Bird { Name =  "Robin", Color = "Red", Sightings = 5 }
};

var yourBirds = new List<Bird> 
{ 
    new Bird { Name =  "Dove", Color = "White", Sightings = 2 },
    new Bird { Name =  "Robin", Color = "Red", Sightings = 5 },
    new Bird { Name =  "Canary", Color = "Yellow", Sightings = 0 }
};
var ourBirds = myBirds.Join(yourBirds,
                            m => m.Name,
                            y => y.Name,
                            bird => myBirds);

1 Answer

Steven Parker
Steven Parker
229,788 Points

You're close. But the final argument to .Join (the resultSelector) should be a Func<TOuter, TInner, TResult>

This means it takes two arguments and returns a result (which in this case can be either of the arguments).

So if we modify that call like this, your method syntax version should also pass the challenge:

var ourBirds = myBirds.Join(yourBirds,
                            m => m.Name,
                            y => y.Name,
                            (m, y) => m);

Happy coding! Β  -sp:sparkles:

Scott Tucker
Scott Tucker
3,765 Points

This worked. Thank you so much!