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copied!<p>This is an issue as old as the Repository pattern itself. The recent introduction of LINQ's <code>IQueryable</code>, a uniform representation of a query, has caused a lot of discussion about this very topic.</p> <p>I prefer specific repositories myself, after having worked very hard to build a generic repository framework. No matter what clever mechanism I tried, I always ended up at the same problem: a repository is a part of the domain being modeled, and that domain is not generic. Not every entity can be deleted, not every entity can be added, not every entity has a repository. Queries vary wildly; the repository API becomes as unique as the entity itself.</p> <p>A pattern I often use is to have specific repository interfaces, but a base class for the implementations. For example, using LINQ to SQL, you could do:</p> <pre><code>public abstract class Repository<TEntity> { private DataContext _dataContext; protected Repository(DataContext dataContext) { _dataContext = dataContext; } protected IQueryable<TEntity> Query { get { return _dataContext.GetTable<TEntity>(); } } protected void InsertOnCommit(TEntity entity) { _dataContext.GetTable<TEntity>().InsertOnCommit(entity); } protected void DeleteOnCommit(TEntity entity) { _dataContext.GetTable<TEntity>().DeleteOnCommit(entity); } } </code></pre> <p>Replace <code>DataContext</code> with your unit-of-work of choice. An example implementation might be:</p> <pre><code>public interface IUserRepository { User GetById(int id); IQueryable<User> GetLockedOutUsers(); void Insert(User user); } public class UserRepository : Repository<User>, IUserRepository { public UserRepository(DataContext dataContext) : base(dataContext) {} public User GetById(int id) { return Query.Where(user => user.Id == id).SingleOrDefault(); } public IQueryable<User> GetLockedOutUsers() { return Query.Where(user => user.IsLockedOut); } public void Insert(User user) { InsertOnCommit(user); } } </code></pre> <p>Notice the public API of the repository does not allow users to be deleted. Also, exposing <code>IQueryable</code> is a whole other can of worms - there are as many opinions as belly buttons on that topic. </p>

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