Solution to Square rectangle problem

We have already gone through this problem here.
So inheritance is not always useful, but composition may be the key sometimes.

public class Square  
 {  
     private Rectangle r;  
     public void SetWidth (double x) { r.SetWidth (x); r.SetHeight (x); }  
     public void SetHeight (double x) { r.SetWidth (x); r.SetHeight (x); }  
     public void GetWidth () { return r.GetWidth; }  
     public void GetHeight() { return r. GetHeight; }  
     public void GetArea () { return r. GetArea; }  
}

So it solves our problem.