用泛型覆盖抽象方法

Question

I have an abstract base class that is defined like this:

public abstract class MyBaseClass<T>

The class contains a definition for the method Get:

protected abstract MyBaseClass<T> Get(T id);

I create MyClass using MyBaseClass:

public class MyClass : MyBaseClass<string>

Now I have to implement Get , but don't know how to define it:

public override MyClass Get(object id)

or

public override MyClass Get(string id)

In both cases I will have to mention string as T and I would like to avoid it.

What is the correct way to override Get ?

Thank You.

Answer 1

When you stated the interface you were implementing you specified the generic argument as string when you wrote ( : MyBaseClass<string> ), as such the only way for you to implement the Get method is to use string in place of all values for T . If you want users of your class to be able to use other types then you need to make the implementing class generic as well:

public class MyClass<T> : MyBaseClass<T>
{
    protected override MyBaseClass<T> Get(T id)
    {
        throw new NotImplementedException();
    }
}

Answer 2

public abstract class MyBaseClass<T>
{
    protected abstract MyBaseClass<T> Get(T id);
}

public class MyClass : MyBaseClass<string>
{
    protected override MyBaseClass<string> Get(string id)
    {
        return FindById(id);//implement your logic
    }
}

Answer 3

Implement abstaract class as follows:

public abstract class  MyBaseClass<T>
{
    protected abstract MyBaseClass<T> Get(T id);

    protected abstract MyBaseClass<T> Get(string id);
}

And the extending class:

class Class1 : MyBaseClass<Object>
{
    protected override MyBaseClass<object> Get(object id)
    {
        return (MyBaseClass<object>) id;
    }

    protected override MyBaseClass<object> Get(string id)
    {
        return FindMyBaseClass(id)
    }
}