How to include a child object's child object in Entity Framework 5

entity-framework entity-framework-4 entity-framework-5 entity-framework-4.1

I am using Entity Framework 5 code first and ASP.NET MVC 3.

I am struggling to get a child object's child object to populate. Below are my classes..

Application class;

public class Application
{
     // Partial list of properties

     public virtual ICollection<Child> Children { get; set; }
}

Child class:

public class Child
{
     // Partial list of properties

     public int ChildRelationshipTypeId { get; set; }

     public virtual ChildRelationshipType ChildRelationshipType { get; set; }
}

ChildRelationshipType class:

public class ChildRelationshipType
{
     public int Id { get; set; }

     public string Name { get; set; }
}

Part of GetAll method in the repository to return all the applications:

return DatabaseContext.Applications
     .Include("Children");

The Child class contains a reference to the ChildRelationshipType class. To work with an application's children I would have something like this:

foreach (Child child in application.Children)
{
     string childName = child.ChildRelationshipType.Name;
}

I get an error here that the object context is already closed.

How do I specify that each child object must include the ChildRelationshipType object like what I did above?

Possible duplicate of Entity Framework - Include Multiple Levels of Properties

Ryan Amies

If you include the library System.Data.Entity you can use an overload of the Include() method which takes a lambda expression instead of a string. You can then Select() over children with Linq expressions rather than string paths.

return DatabaseContext.Applications
     .Include(a => a.Children.Select(c => c.ChildRelationshipType));

As GraemeMiller said, strongly typed classes are better for maintainability than using strings

Which version did the lamba method come available? I'm stuck on a EF 4.0 Codebase..and cant' get the lamdas to work. Thanks for any input.

It will work in EF 4, just make sure to add a reference to System.Data.Entity;

FYI - In EF 6 the namespace is Microsoft.Data.Entity

Using EF 5, I could not get .Select(x => x.Child) but this worked - Entities.UserProfile storedProfile = db.UserProfiles .Include(s => s.ShippingAddress) .Include(st => st.ShippingAddress.StateProvince) .Include(b => b.BillingAddress) .Include(bs => bs.BillingAddress.StateProvince) .FirstOrDefault(x => x.UserId == userId);

Hayha

With EF Core in .NET Core you can use the keyword ThenInclude :

return DatabaseContext.Applications
 .Include(a => a.Children).ThenInclude(c => c.ChildRelationshipType);

Include childs from childrens collection :

return DatabaseContext.Applications
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType1)
 .Include(a => a.Childrens).ThenInclude(cs => cs.ChildRelationshipType2);

Thanks!!! Really helpful! Sometimes you might get wrong intellisense, just ignore that and build! :)

Nice one, I was looking for .net core :)

And what if Children is a collection and I need to include properties under it?

Found an overload for that. Was not obvious at first.

@dodbrian What was the overload? I'm trying to nest .ThenInclude, where the child is a collection.

mattruma

I ended up doing the following and it works:

return DatabaseContext.Applications
     .Include("Children.ChildRelationshipType");

The strongly typed way is better. Magic strings aren't good for refactoring

gcoleman0828

A good example of using the Generic Repository pattern and implementing a generic solution for this might look something like this.

public IList<TEntity> Get<TParamater>(IList<Expression<Func<TEntity, TParamater>>> includeProperties)

{

    foreach (var include in includeProperties)
     {

        query = query.Include(include);
     }

        return query.ToList();
}

How would I call the above method? could you provide an example

@Jamee -List>> includers = new List>>(); includers.Add(x => x.FirstName); Get(includers);

And query comes from...?

Sorry @DougBeard, not following your question.

@gcoleman0828 The query variable in your code snippet above. Is it magically instantiated? Where does it come from?

How to include a child object's child object in Entity Framework 5

Follow WeChat

Want to stay one step ahead of the latest teleworks?

相似问题

Platform

Support

Links

Contact US