Override Property with different compatible Type

Question

I need a base class with a property where I can derive classes with the same property but different (compatible) types. The base Class can be abstract.

public class Base {     public virtual object prop { get; set; } }  public class StrBase : Base {     public override string prop { get; set; } // compiler error }  public class UseIt {     public void use()     {         List<Base> l = new List<Base>();         //...     } } 

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I tried it with Generics but that gives me a problem when using the class, because I want to store differently typed base classes in the List.

public class BaseG<T> {     public T prop { get; set; } }  public class UseIt {     public void use()     {         List<BaseG> l = new List<BaseG>(); // requires type argument         //...     } } 

Answer 1

Here's an alternative approach to proposed solution:

public abstract class Base {     public abstract void Use();     public abstract object GetProp(); }  public abstract class GenericBase<T> : Base {     public T Prop { get; set; }      public override object GetProp()     {         return Prop;     } }  public class StrBase : GenericBase<string> {     public override void Use()     {         Console.WriteLine("Using string: {0}", Prop);     } }  public class IntBase : GenericBase<int> {     public override void Use()     {         Console.WriteLine("Using int: {0}", Prop);     } } 

Basically I've added a generic class in the middle that stores your properly-typed property. this will work assuming that you never need to access Prop from the code that iterates the members of the List<Base>. (You could always add an abstract method to Base called GetProp that casts the generic to an object if that's required.)

Sample usage:

class Program {     static void Main(string[] args)     {         List<Base> l = new List<Base>();          l.Add(new StrBase {Prop = "foo"});         l.Add(new IntBase {Prop = 42});          Console.WriteLine("Using each item");         foreach (var o in l)         {             o.Use();         }         Console.WriteLine("Done");         Console.ReadKey();     } } 

Edit: Added the GetProp() method to illustrate how the property can be directly accessed from the base class.