Question

So i think i maybe over-complicating things in my implementation, but here’s what i’m doing:

1. I want my database represented by IRepository
2. SQLRepository is a concrete implementation of IRepository.
3. I want all Tables in the Database represented by ITable.
4. I have a table called Items, which is represented by ItemsTable.
5. Each record in Items Table is represented by IItem.
6. Item is a concrete implementation of IItem.

Now my problem is, in my program when i want to use List items = repository.Items.List(); it won’t compile because in ItemsTable the implementation of ITable return IList and not List. I could return IList but i do want to work with a concrete List of Items.

What can i do better?

 public interface ITable
    {
        IList<IItem> List();
        bool Add(IItem item);
        bool Delete(long itemId);
        bool Find(long itemId);
    }

public class ItemsTable : ITable
{
    public IList<IItem> List()
    {
        IList<IItem> items = GetItems(); // GetItems return List<Item>, Item implements IItem.
        return items;
    }

   .....
   ...
   ..
}

public class SQLRepository : IRepository
{
    ITable items = new ItemsTable();

    public ITable Items
    {
        get { return items; }
    }
}


    static void Main(string[] args)
    {
        var repository = new SQLRepository();
        List<Item> items = repository.Items.List();
    }

Answer 1

The best would be changing your interface to:

public interface ITable<TItem>
    where TItem : IItem
{
    IList<TItem> List();
    bool Add(TItem item);
    bool Delete(long itemId);
    bool Find(long itemId);
}