Exclude related entities even if DbContext has loaded them

Question

Is there a way I can get a list of EntityA without its related navigations, even when DbContext has them. I need this for serialization purposes.

I tried to turn Lazy loading off and explicitly .Include any related entities. But if DbContext has already loaded them, it will be included anyway.

The senario is like this:

public class LookupRepository : ILookupRepository
{
    private readonly CustomDbContext _dbContext;

    public LookupRepository(CustomDbContext dbContext) {
        if(dbContext == null)
            throw new ArgumentNullException("dbContext");

        _dbContext = dbContext;
    }

    public IEnumerable<Country> GetCountriesFull() {
        return _dbContext.Set<Country>()
            .Include(c => c.Areas)
            .Include(c => c.Continent)                
            .ToList();
    }

    public IEnumerable<Country> GetCountries() {
        return _dbContext.Set<Country>()
            .ToList();
    }

    public IEnumerable<Continent> GetContinents() {
        return _dbContext.Set<Continent>()
            .ToList();
    }

    public IEnumerable<Area> GetAreas() {
        return _dbContext.Set<Area>()
            .ToList();
    }       
}

And the DbContext I inject in there is initialized like this:

public CustomDbContext CreateDbContext(){
    var dbContext = new CustomDbContext();
    dbContext.Configuration.ProxyCreationEnabled = false;
    return dbContext;
}

So this test that uses a clean DbContext passes:

[Test]
public void GetCountries_CalledOnce_ReturnsCountriesWithoutNavigations() {
    var sut = CreateLookupRepository();
    var countries = sut.GetCountries();

    CollectionAssert.IsNotEmpty(countries);
    Assert.That(countries.Select(c => c.Continent), Is.All.Null);
    Assert.That(countries.Select(c => c.Areas), Is.All.Null);
}

but this one that includes all a call to GetCountriesFull fails:

[Test]
public void GetCountries_AfterCallingGetCountriesFull_StillReturnsNoNavigations() {
    var sut = CreateLookupRepository();
    var fullCountries = sut.GetCountriesFull();
    var countries = sut.GetCountries();

    CollectionAssert.IsNotEmpty(countries);
    Assert.That(countries.Select(c => c.Continent), Is.All.Null);
    Assert.That(countries.Select(c => c.Areas), Is.All.Null);
}

Any advice on how to do this? I thought of using a factory to create a new dbContext for each method (anyway this code is only run on my application startup and data remain in memory as Singleton), but I thought there must me a better solution.

@cleftheris I m serializing in json, but I wouldn't like to depend on that (especially in my Domain models). — zafeiris.m, May 14 '14 at 12:16

Gert Arnold · Answer 1 · 2014-05-14T22:30:01.793

The most simple way to do this is by getting the entities with AsNoTracking(). By doing this, you tell EF not to add the entities to its internal cache and entity relationships will not be resolved.

But here (again) the extra repository layer works against you, because you can't just do a call like

var fullCountries = sut.GetCountriesFull().AsNoTracking();

You have to make overloads, or add parameters like bool withTracking, or initialize the repository with an option to always (or never) use AsNoTracking().

score 1 · Answer 2 · answered May 14 '14 at 10:39

1

If you don't care that they are being loaded unnecessarily (or they were already filled in for another reason), just set all navigational properties to null if you don't want them to be passed.

You can also add the [XmlIgnore] attribute to your navigational properties, so the serializer will not include them. That also prevents the same issue.

answered May 14 '14 at 10:39

Flater

12,908
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Interesting. Well I suppose I should add `[XmlIgnore]` and `[JsonIgnore]` in my model which I wouldn't like, but certainly is a way that solves my problem, thanks. – zafeiris.m May 14 '14 at 10:54
Also to have all navigation properties to `null` I should add sth like _dbContext.Set().Select(c => new Country{...}) and in the `...` part I should add all properties. Again it solves the problem but I was wondering if there is some EF solution like `Exclude` or sth that does not need such maintenance headache from my side. – zafeiris.m May 14 '14 at 10:58
`[XmlIgnore]` is the exact same thing as what you would expect from an exclude statement, but it's a property for the serializer. Excluding is not really an EF option as a simple null assignment does the same thing :) – Flater May 14 '14 at 11:00
@zafeiris.m: Also, I'd not put the null assignments inside of the select statement. After you've selected the needed entities, iterate over them while setting all needed navprops to null. The performance hit is negligible (especially compared to the time needed to load them in the first place). – Flater May 14 '14 at 11:01

score -1 · Answer 3 · answered May 14 '14 at 10:49

Dear there are many ways to doing it 1)if you are using code 1st then follow this

protected override void OnModelCreating(DbModelBuilder modelBuilder) {
 base.Configuration.LazyLoadingEnabled = false;
}

2)The edmx file has in the and definition an attribute for lazy loading where you can set lazy loading generally to false:

public MyEntitiesContext() : base("name=MyEntitiesContext", "MyEntitiesContext")
{
this.ContextOptions.LazyLoadingEnabled = false;
OnContextCreated();
}

or simply do this

public BlogContext() : base()
{
this.Configuration.LazyLoadingEnabled = false;
}

Exclude related entities even if DbContext has loaded them

3 Answers3