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# Computed Propeties

I have watched the video a couple of times now and I cant figure this method of coding out. I dont get it. I need to write the computed property. I have tried multiple ways now and I cant get it.

Square.cs
```namespace Treehouse.CodeChallenges
{
class Square : Polygon
{
public double SideLength { get; private set; }
public double Area {get {area}}

public Square(double sideLength) : base(4)
{
SideLength = sideLength;
}
}
}
```
Polygon.cs
```namespace Treehouse.CodeChallenges
{
public class Polygon
{
public int NumSides { get; private set; }

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

A computed property is essentially just a method that gets treated like a property. In the sense that it can be used exactly like a property would be used normally but when you reference it you don't just pull out a value already stored in it like you do with normal properties, you actually run a method and get what the method ends up returning.

You place the method you want to run in brackets directly following the get keyword. So if you for example wanted a computer property that was called TwoPlusTwo that simply calculated what 2+2 is each time it was called it would be written like this:

```public int TwoPlusTwo {
get {
return 2 + 2;
}
}
```

That computed property would of course return 4, and while it's a fairly useless computed property it does show you how computed properties are structured. In order to calculate the area of a square you multiply the sides together, so the solution to this challenge simply looks like this:

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

You don't need to define any read only properties or anything like that to solve this challenge.

Ok cause it kept asking if my variable was a readonly which is why I kept doing that. Thanks a bunch!!!! Cleared it up nicely.

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

```    public double Area { // This is a property but treated as the method because it is a computed property.
get {
return SideLength * SideLength;
}
}

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

}

The computed property needs to look more like this. It's important to include the return; public double Area { get { return SideLength * SideLength ; } }