Architecture abstraction problem in Repository ASP.NET MVC?

Public User GetUser(Expression> restriction) { return db.Users. Where(restriction).FirstOrDefault(); } Now use it: var you = Repository. GetUser(u => u.Logs.

Any(l => l.id. Equals(log. Id))) You can also use MS DynamicQuery : using System.Linq.

Dynamic; //... public User GetUser(string propertyName, int id) { var restriction = propertyName + ". Any(id = @0)"; return db.Users. Where(restriction, id).FirstOrDefault(); } var you = Repository.

GetUser("Logs", log. Id) I may not have the syntax quite correct, but you get the idea.

Public User GetUser(Expression> restriction) { return db.Users. Where(restriction).FirstOrDefault(); } Now use it: var you = Repository. GetUser(u => u.Logs.

Any(l => l.id. Equals(log. Id))); You can also use MS DynamicQuery: using System.Linq.

Dynamic; //... public User GetUser(string propertyName, int id) { var restriction = propertyName + ". Any(id = @0)"; return db.Users. Where(restriction, id).FirstOrDefault(); } var you = Repository.

GetUser("Logs", log. Id); I may not have the syntax quite correct, but you get the idea.

Great. But I need a "more automated" expression, maybe using the class name. – Sig.

Tolleranza Jan 21 '10 at 13:54 Then use MS Dynamic LINQ to do the same thing. I'll update the example. – Craig Stuntz Jan 21 '10 at 14:22 Thanks, I think I'll try the last one you suggest.

– Sig. Tolleranza Jan 25 '10 at 11:42.

If all the associated entities (Log, Product and Photo) will be searched by a common property (id INT) then maybe you could try something like this... First, create an interface: public interface IUserAssociation { int id { get; } } Then each of the three classes would implement this interface like so: public partial class Product : IUserAssociation { } The the GetUser method would look like so: public User GetUser(T entity) where T : IUserAssociation { var type = typeof(T); if (type == typeof(Log)) { return db.Users. FirstOrDefault(u => u.Logs. Any(l => l.id.

Equals(entity. Id))); } else if (type == typeof(Product)) { return db.Users. FirstOrDefault(u => u.Products.

Any(pr => pr.id. Equals(entity. Id))); } else if (type == typeof(Photo)) { return db.Users.

FirstOrDefault(u => u.Photos. Any(ph => ph.id. Equals(entity.Id))); } else { throw new ArgumentException(); } } Then you should be able to call GetUser and pass it a Log, Photo or Product entity from one method.

It is not very elegant but would work for this specific situation.

I like Craig's solution better but I'd suggest this: Repository. GetUser(u => u. Logs, log); Which will be possible if all your entities derive from public interface IEntity { public int Id { get; } } Then method will be like public User GetUser(Func> getlist, Y sample) where T: IEntity where Y: IEntity { return db.Users.

Select(x => getlist(x). Any(y => y. Id == sample.Id)).FirstOrDefault(); } Also if we take idea of S#arp Architecture that if entity1.

Id == entity2. Id (for persistent entities) then Equals(entity1, entity2) - we can use getlist(x). Contains(sample).

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