具有不同实现的泛型基类中的属性

Question

I've got an abstract class CommandBase<T, X> that I want to have a property InnerCommand .

But since the InnerCommand might have other types for T and X than the command that contains it, how can I define that?

The abstract class:

public abstract class CommandBase<T, X>
    where T : CommandResultBase
    where X : CommandBase<T, X>
{
    public CommandBase<T, X> InnerCommand { get; set; }
    (...)
}

In the example above InnerCommand will only accept instances that have the same types for T and X, but I need to allow for other types.

An AddOrderitemCommand:

public class AddOrderitemCommand : CommandBase<AddOrderitemResult, AddOrderitemCommand>
{
    (...)
}  

Might contain a WebserviceCommand:

public class GetMenuCommand : CommandBase<GetMenuResult,GetMenuCommand>
{
    (...)
}

Please advise on the syntax for allowing this.

Answer 1

You basically have three options:

1. Use dynamic as the type of that property. Nothing I would do.
2. Use object as the type of that property. Nothing I would do.
3. Create a non-generic base class or interface for commands. Make CommandBase<T, X> implement it and use it as the type of the property. That's the way I would go.

Answer 2

If the InnerCommand doesn't relate to the parent T / X , then I would suggest using a non-generic InnerCommand that doesn't advertise the type in the signature. This may mean adding a non-generic base-type ( CommandBase ) or an interface ( ICommandBase ). Then you can simply use:

public ICommandBase InnerCommand {get;set;}
// note : CommandBase<T,X> : ICommandBase

or

public CommandBase InnerCommand {get;set;}
// note : CommandBase<T,X> : CommandBase