Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

C# C# Objects Inheritance Inheritance

The Polygon class represents a 2 dimensional shape. It has a public field named NumSides. Create a new type of polygon c

Hey Team,

I am new to C#, need a bit of help in understanding the completing this question. I keep on getting with the attached code.

Polygon.cs
namespace Treehouse.CodeChallenges
{
    class Polygon
    {
        public readonly int NumSides;

        public Polygon(int numSides)
        {
            NumSides = numSides;
        }
    }
    class Square : Polygon
    {
     public readonly int SideLength;

     public Square(int sideLength)
     {
     base.Numsides = 4;
     }

    }
}

1 Answer

Steven Parker
Steven Parker
216,020 Points

Since "NumSides" (note: spelled with capital "S") is readonly, it cannot be assigned to except by calling the base constructor. This is done with the colon syntax when defining the derived class constructor:

     public Square(int sideLength) : base(4)

Hi Steven,

Thanks for the response. I did try the above syntax and now I started to get a new error:

"Polygon.cs(14,5): error CS1519: Unexpected symbol `}' in class, struct, or interface member declaration"

Code:

namespace Treehouse.CodeChallenges { class Polygon { public readonly int NumSides;

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

class Square : Polygon
{
    public readonly int SideLength;
    public Square(int sideLength) : base(4)
}

}

Steven Parker
Steven Parker
216,020 Points

The constructor still needs a body in which the argument will be stored in the field, similar to what is done in the "Polygon" class.