.net,linq,entity-framework,include,condition , LINQ to SQL: How to create something like conditional include?


LINQ to SQL: How to create something like conditional include?

Question:

Tag: .net,linq,entity-framework,include,condition

I'd like to create a query contains User whose entities has Event with type == 1. I would also like the Event entries loaded into EventsCollection. My code would be something like .Include(u => u.EventsCollection), but this only loads all Event entries - I want to load only with type == 1.

I have simple model like this:

public class User
{
    public int UserId { get; set; }

    public ICollection<Event> EventsCollection { get; set; }
}
public class Event
{
    public int EventId { get; set; }
    public int UserId { get; set; }
    public int Type { get; set; }

    public User User {get; set; }
}

Any ideas?

Edit:

Finally I've found the solution: We need fresh DataContext object with NO Event entities have been previously loaded.

Then we need to filter Events like this:

var filteredEventsCollection = db.Events
    .Where(ev => ev.Type == 1)
    .ToList(); //Materialize query here

Now we should query users like this:

var usersWithFilteredEvents = db.Users
    .Where(u => u.EventsCollection.Any(ev => ev.Type == 1))
    .ToList();

And that is all! EF will substitute EventsCollection with data from the first query by itself.


Answer:

If you are only trying to get the events where userID ==1, you can use the following. This will give you only the event you need from the Event Collection for the user.

        User u = new User()
        {
            UserId = 60
        };

        Event e1 = new Event() { EventId = 1, UserId = 2, Type = 3, User = u };
        Event e2 = new Event() { EventId = 2, UserId = 3, Type = 4, User = u };
        Event e3 = new Event() { EventId = 3, UserId = 4, Type = 5, User = u };
        Event e_Test = new Event() { EventId = 7, UserId = 1, Type = 5, User = u };

        u.EventsCollection = new List<Event>();

        u.EventsCollection.Add(e1);
        u.EventsCollection.Add(e2); 
        u.EventsCollection.Add(e3);
        u.EventsCollection.Add(e_Test);


        var h = from use in u.EventsCollection where use.UserId == 1 select use;

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