如何定义继承通用抽象类的通用抽象类？

Question

I have a class that inherits an abstract class which inherits another abstract class. I can define the most-super class as being generic just fine, but I don't know how to define the middle class as being generic before I express the actual type I want in the final ListResults class.

internal abstract class LowerCommand<T> {
    public abstract void Execute();
    public abstract List<T> ExecuteList();
}

// currently gives error for `T`
internal abstract class HigherCommand : Lowercommand<T> {
    // ... defines other stuff, nothing to do with
    //     already instantiated methods or T ...
}

class ListResults : HigherCommand<Results>
{
    public override void Execute() {...}
    public override List<Results> ExecuteList() {...}
}

Thanks for your help.

Answer 1

You still need to define the generic type parameter T on the definition of HigherCommand so it can in turn properly define LowerComand .

internal abstract class LowerCommand<T> {
    public abstract void Execute();
    public abstract List<T> ExecuteList();
}

// Note that HigherCommand require a declaration of `T`
internal abstract class HigherCommand<T> : Lowercommand<T> {
    // ... defines other stuff, nothing to do with
    //     already instantiated methods or T ...
}

class ListResults : HigherCommand<Results>
{
    public override void Execute() {...}
    public override List<Results> ExecuteList() {...}
}