Question

I have base class and two inherited classes, these two inherited classes also share the two properties. I would like to access these properties from base class. How to do that? Example below.

public abstract class ClientEngine
{
        public void SaveFile(string fileName);
        {
            //Not implemented, I get error here because I don't know how to access Inherited class properties
            if (FileStorage != null))
                File.WriteAllBytes(fileName, FileStorage);
        }
}

    public interface IEngineEntity
    {
        byte[] FileStorage { get; set; }
    }

public class MyEntity1 : ClientEngine, IEngineEntity
{

public string MyProperty1 {get; set;}
public string MyProperty2 {get; set;}

public byte[] FileStorage { get; set; }
}

public class MyEntity2 : ClientEngine, IEngineEntity
{

public string MyProperty3 {get; set;}
public string MyProperty4 {get; set;}

public byte[] FileStorage { get; set; }
}

Answer 1

If you need to access a property from the base class, you are doing something wrong. Keep that in mind for your future designs.

You should declare FileStorage in the base class, since both inherited classes have it.

If you do not want to define FileStorage‘s specific type (say, byte[]), you might want to define it as a more generic type, such as IEnumerable<byte>. Alternatively, you can declare FileStorage as an interface who provides whatever behavior you need to access from base class.

Update

A nice observation by @ghimireniraj: you should also try to derive ClientEngine from IEngineEntity. One of the bottom lines for OO design is that if you replicate behavior in all inherited classes, it should be in the base class.

But, do you really want to access some code from base class? You shouldn’t. But if you really need, you can always cast:

public abstract class ClientEngine
{
    public void SaveFile(string fileName);
    {
        byte[] fileStorage = null;
        if (this is MyEntity1)
        {
            MyEntity1 me1 = (MyEntity1)this;
            fileStorage = me1.FileStorage;
        }
        else if (this is MyEntity2)
        {
            MyEntity2 me2 = (MyEntity2)this;
            fileStorage = me2.FileStorage;
        }
        if (fileStorage != null))
            File.WriteAllBytes(fileName, fileStorage);
    }
}

Nasty right? But it should look dirty, because we are trying to break OO design.

Update

Another way is going by Marc Gravell’s suggestion. Instead of casting to the types, cast to the interface. But all of this still smells bad to me: I firmly believe you can improve your design.