CODEWITHSUNDEEP
c#entity-framework-core-2.2
Teeseesee
Teeseesee

Reputation: 31

How to stop Entity Framework from including properties I don't want it to?

When reading an entity type from my DataContext, I get all the associated objects when I don't want them. How do I set EF up so I only do explicit loading?

Reading up on msdn info like from here: https://devblogs.microsoft.com/dotnet/announcing-entity-framework-core-2-2/

It seems like I should get nothing for free, so explicit loading is the way, however I'm using the code below but my results are more than I would expect.

public class TalesContext : DbContext
{
    public TalesContext()
    {
    }

    public TalesContext(DbContextOptions<TalesContext> options) : base(options)
    {
    }

    protected internal DbSet<Story> Stories { get; set; }
    protected internal DbSet<Event> Events { get; set; }
    protected internal DbSet<StoryEventMention> EventMentions { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (optionsBuilder.IsConfigured) return;

        optionsBuilder.UseInMemoryDatabase("TalesTesting");
    }
}

public class Event
{
    [Required]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public IList<StoryEventMention> EventMentions { get; set; }
    [MaxLength(128)]
    public string Title { get; set; }
}


var query = from e in TalesContext.Events select e;
// various query.Where
query = query.Skip((pageNumber - 1) * pageSize).Take(pageSize);
return query.ToList();

I would expect to get a list of Events with the Ids and Titles populated and EventMentions as null. However I get EventMentions populated along with all further navigation properties. Pretty much the entire test database.

I get this when I run a unit test and when I expose this through an API.

Upvotes: 0

Views: 570

Answers (2)

Teeseesee
Teeseesee

Reputation: 31

I found my mistake.

My EventFetcher class is a singleton, registered through IoC. It has a reference to TalesContext also registered as a singleton through IoC. So I had one DataContext through the application. So when the first request came in, it seeded the database - and so had everything in it. Thus all the references between the objects were already built and when I requested one without explicitly including it, the context returned the data it already had with everything attached.

I did a restructure on this so that a new context is injected into the controller each request and the behaviour is exactly what you would expect. So the lesson here is to be mindful of the age and persistence of your data context if you start getting unexpected results when querying.

Thanks for the assistance!

Upvotes: 1

A.sharif
A.sharif

Reputation: 2017

To answer your question. I believe what you need to do is inside your TalesContext call this :

this.Configuration.LazyLoadingEnabled = false;

Sources: explains lazy loading: https://www.entityframeworktutorial.net/lazyloading-in-entity-framework.aspx

Explains the difference between eager loading and lazy loading https://learn.microsoft.com/en-us/aspnet/mvc/overview/getting-started/getting-started-with-ef-using-mvc/reading-related-data-with-the-entity-framework-in-an-asp-net-mvc-application

Upvotes: 0

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