Syntactic Sugar

I'm struggling through this course, I've never done anything like this so please be kind, it's been a fight to get to here. What am I misunderstanding or not grasping? Re-watching the videos now.

Link: https://teamtreehouse.com/community/cant-solve-challenge-1-of-2

Question: Use the syntactic sugar just learned about to convert the Area property to a single line property.

Given Code: namespace Treehouse.CodeChallenges { class Square : Polygon { public double SideLength { get; private set; }

    public double Area 
    { 
        get { return SideLength * SideLength; } 
    }

    public Square(double sideLength) : base(4)
    {
        SideLength = sideLength;
    }

    public void Scale(double factor)
    {
        SideLength *= factor;
    }
}

}

My wrong answer, rather one variable of it: namespace Treehouse.CodeChallenges { class Polygon { public double Area => SideLength * SideLength; } }

namespace Treehouse.CodeChallenges
{
    class Polygon
    {
        public double Area => SideLength * SideLength;
    }
}

namespace Treehouse.CodeChallenges
{
    class Polygon
    {
        public int NumSides { get; private set; }

        public Polygon(int numSides)
        {
            NumSides = numSides;
        }
    }
}