Learning MVC: A Repository Pattern.

A repository is just a place where data querying is encapsulated. There are several main reasons for a repository:

• Avoid repetition. If I need to write a query, I will first check the repository - maybe it was already implemented
• Encapsulation. Keep all data related code in the same place. Makes refactoring easier and separates logic from data
• Unit testing. Tests can be written against the repository and, if necessary, in such way that the real database is not required

For the purpose of my sample application, which I explain later, I will now add a repository for the "In Basket". It's extremely simple: each user can have multiple items in the basket. A user can view, edit and delete any of his items. So I need a small number of methods:

public class InBasketRepository
{
    private modelGTDContainer db = new modelGTDContainer();

    //return all in basket items for a certain user
    public IQueryable FindUserInBasketItems(int userID)
    { 
        return db.InBaskets.Where(item => item.UserID == userID);
    }

    public InBasket GetInBasketItem(int id)
    {
        return db.InBaskets.Single(item => item.InBasketID == id);
    }

    public void AddInBasketItem(InBasket item)
    {
        db.InBaskets.AddObject(item);
    }

    public void DeleteInBasketItem(InBasket item)
    {
        db.InBaskets.DeleteObject(item);
    }

    //persistence
    public void Save()
    {
        db.SaveChanges();
    }
}

It seems logical for the repository to exist in the Models folder.

And that's it for now - the next step is to create view(s) which will use the repository.

by Evgeny. Also posted on my website