A interface and abstract class with static member

[Bryan Cheung]

Hi guys,

So i've read already about its not possible to make a abstract property static but then i'm a bit stuck and hoping you guys can show me a other way.

The setup:

_____________________
___IBaseService
    public interface IBaseService<T> where T : BaseObject
    {
        T get(int id);
        BaseCollection<T> getAll();
        bool add(T obj);
        bool remove(int id);
        bool remove(T obj);
        bool removeAll(BaseCollection<T> collection);
    }
 
___BaseService
public abstract class BaseService
    {
        public abstract string SystemName
        {
            get;
        }
 
        public bool update()
        {
            try
            {
                return true;
            }
            catch (Exception exc)
            {
                return false;
            }
        }
    }
 
___ServicesRepository
public class ServicesRepository
{
    public static string SystemName = "ServicesRepository";
 
    //The services
    private static Dictionary<string, BaseService> services;
 
    //Instance
    private static ServicesRepository instance;
 
    /// <summary>
    /// Get the instance of ServicesRepository
    /// </summary>
    public static ServicesRepository Instance
    {
        get
        {
            if (instance == null)
                instance = new ServicesRepository();
            return instance;
        }
    }
 
    /// <summary>
    /// ServicesRepository: Centralization off the Services.
    /// </summary>
    public ServicesRepository()
    {
        if (services == null)
            this.registerServices();
    }
 
    private void registerServices()
    {
    }
 
    public static BaseService Get(string systemName)
    {
        if (services.ContainsKey(systemName))
            return services[systemName];
        else
            return null;
    }
}

It's a pretty simple setup actually, I believe most of you would use the naming repository but I use Service because my services does a bit more than just keep and get the objects.

What I basiclly want to accomplish it that I can register all my services that are derived from BaseService to have a SystemName so I can register them in the ServicesRepository. Now I just need one instance of the service and want to register it by a name. So I want to be able to do something along of:

UserService userService = ServicesRepository.Get(UserService.SystemName);

So I think(!) I need a static abstact property because I want it to static(call with no instance, if I make a instance I defeat all purpose of this setup) but I want it in the BaseService or IBaseService so all the child classes must have systemName.

Any thoughts?

Many thanks,
Bryan

[hype261]

I don't think you actually need a static abstract property. It looks to me you are trying to implement a Singleton for the ServicesRepository. If this is correct then to access the Service you need to do the following

UserService userService = ServicesRepository.Instance.Get(UserService.SystemName);

Also this function public static BaseService Get(string systemName) shouldn't be static and your constructor for the ServiceRepository is messed up. I would look at the Singleton Design Pattern.

[Bryan Cheung]

Hello hype261,

The ServicesRepository is good right now. The Repository should not be singleton because its.. a repository, I want the possibility to make more then just one. But! there should only be one of each service in it. And the services should also not be singleton because I want to be able to create more then one, because I can have more Repository's then one.

The constructor is fine because I should load the services at construction of the object and then I should register all services to the services property. This way all the services that should(!) be loaded are loaded. Maybe in the future I'll extend it in a way that the services are registered in config file(XML), corresponding with the SystemName.

This way I can have different repository classes with different types of services for different purposes :) and still be easy in use because of the config files(like modules).

Sorry, I should have told before what I exactly wanted.

So, is there a way to enforce the SystemName at the child services but still be static so there is one for each type of service child class?

Kind regards,
Bryan

[Bryan Cheung]

Sorry for the double post, I should register -_- but I see I said "call with no instance, if I make a instance I defeat all purpose of this setup". With this I mean, at the time of getting the service, I don't want to create a new service but get the one from the repository. The repository is kept in a Base class for UserControls so don't worry about that one.

As example but not in use: There could be a repository for the base class of the masterpages and a different repository for the base class of the pages. I see no purpose for that now, but it could be :P and I'd like the option open :)

Kind regards,
Bryan Cheung

[Curtis Rutland]

Why make it abstract? Just make it public static, with an internal set.

Something like this:

class Program
{
    static void Main(string[] args)
    {
        TestBase b = new TestClass();
        Console.WriteLine(TestClass.TestProperty);
        Console.ReadKey();
    }
}
 
public class TestClass : TestBase
{
    static TestClass()
    {
        TestProperty = "TestClass";
    }
}
 
public abstract class TestBase
{
    public static string TestProperty { get; internal set; }
 
    static TestBase()
    {
        TestProperty = "TestBase";
    }
}

Let me know if I completely missed the point.

[Bryan Cheung]

Hi Curtis,

But this way, you don't enforce TestProperty, in the subclasses, right? you give it a default. I'll keep this one in mind as my last resort if I cant solve it.

-Bryan