Question

I have a base class that does calculations on image sizes. I’m deriving a class from that and have predefined image sizes that will be used in my code. While what I have works, I have a strong feeling that I’m not doing it properly.

Ideally, I’d like to just pass DerviedClass.PreviewSize as the parameter to GetWidth without having to create an instance of it.

class Program {     static void Main(string[] args)     {         ProfilePics d = new ProfilePics();         Guid UserId = Guid.NewGuid();          ProfilePics.Preview PreviewSize = new ProfilePics.Preview();         d.Save(UserId, PreviewSize);     } }  class ProfilePicsBase {     public interface ISize     {         int Width { get; }         int Height { get; }     }      public void Save(Guid UserId, ISize Size)     {         string PicPath = GetTempPath(UserId);         Media.ResizeImage(PicPath, Size.Width, Size.Height);     } }  class ProfilePics : ProfilePicsBase {     public class Preview : ISize     {         public int Width { get { return 200; } }         public int Height { get { return 160; } }     } } 

Answer 1

It seems to me that you want a more flexible implementation of ISize – having an implementation which always returns the same value seems fairly pointless. On the other hand, I can see that you want an easy way of getting the size that you always use for a preview. I would do it like this:

// Immutable implementation of ISize public class FixedSize : ISize {     public static readonly FixedSize Preview = new FixedSize(200, 160);      private readonly int width;     private readonly int height;      public int Width { get { return width; } }     public int Height { get { return height; } }      public FixedSize(int width, int height)     {         this.width = width;         this.height = height;     } } 

You could then write:

ProfilePics d = new ProfilePics(); Guid userId = Guid.NewGuid();  d.Save(userId, FixedSize.Preview); 

This would reuse the same instance of FixedSize whenever you called it.