C# generic class inheritance

Question

I have a base class BaseRepository which other classes extend.

public class BaseRepository
{
    protected RestClient client;
    protected string url;

    public BaseRepository ()
    {
        client = RestClient.GetInstance ();
    }

    public async Task<T> Find<T> (string id) {
        dynamic response = await client.Find(url, id);

        return DeserializeItem<T> (response);
    }
}

and then I have a UsersRepository class which extends from the base class.

public class UsersRepository : BaseRepository
{
    string url = "users";
    static UsersRepository instance;

    private UsersRepository ()
    {
    }

    public static UsersRepository GetInstance() {
        if (instance == null) {
            instance = new UsersRepository ();
        }

        return instance;
    }
}

I can't figure out how to pass User as the response type for the public async Task<T> Find<T> (string id) method. I could create this method in the UsersRepository but I do not want to duplicate the code.

public override function User Find(string id) {
    return base.Find<User>(id);
}

Any help would be much appreciated.

Answer 1

It looks like you actually want the generic type defined on the base class and not the method. Also I think you want to set the url defined in the base class in the constructor of the derived class.

public class BaseRepository<T>
{
    protected RestClient client;
    protected string url;

    public BaseRepository ()
    {
        client = RestClient.GetInstance ();
    }

    public async Task<T> Find(string id) {
        dynamic response = await client.Find(url, id);

        return DeserializeItem<T> (response);
    }
}

public class UsersRepository : BaseRepository<User>
{
    static UsersRepository instance;

    private UsersRepository ()
    {
        url = "users";
    }

    public static UsersRepository GetInstance() {
        if (instance == null) {
            instance = new UsersRepository ();
        }

        return instance;
    }
}