是否可以为不同类型创建通用抽象父类？

Question

I was curious if it was possible to create like a parent abstract class that I can define a specific set of methods in but have the children classes include different entity types? Code Example:

public abstract class BaseService
{
    public abstract void Add();

    public abstract void Delete();

    public abstract void Update();

    public abstract void Get();        
}

Maybe be able to do something like public abstract List<'random type'> GetAll();

But here i would want to override each method with specific parameters that are specific to each of its children:

public class CategoryService : BaseService
{
    public override void Add(){ }

    public override void Delete(){ }

    public override void Update(){ }

    public override void Get(){ }
}

However, in my child class, I would want my Get() method to return a specific List<"of Type"> (in this case Category). Furthermore, I might want to do public override Add(int CategoryID) instead of the inherited Add from BaseService .

Is this possible? Thoughts? Am I just crazy? Or am I trying to make this more complicated than it needs to be? I have about 10 different service types that I want to make sure get those generic methods from BaseService .

Thanks in advance!

Answer 1

You could do this if I understand you correctly:

public abstract class BaseService<T>
{
    public abstract T Get();        
}

Then:

public class CategoryService : BaseService<Category>
{
    public override Category Get(){ ... }
}

You can't override methods and have a different signature in the override, but you could use a dictionary/hashtable or something more fancy to pass parameters into the Add method. Passing parameters in using a generic container would mean you are starting to use the query pattern where the parameters in the container determine the query (just for info :-)).

Answer 2

Try using generic type

public abstract List<T> GetAll<T>();

And return appropriate type in your child class

Update

@pw94 answer is also a good way to achieve this, but the only problem is you cannot have multiple type for different methods, only one type will work once you inherit the class.

Answer 3

You can create abstract generic class:

public abstract class BaseService<T>
{
    public abstract void Add();

    public abstract List<T> Get();        
}

And implement:

public class CategoryService : BaseService<int>
{
    public override void Add(){ ... }

    public override List<int> Get(){ ... }
}