Loading related entities with Entity Framework 6

Question

This is my second day with EntityFramework and I have another problem:

I'm saving some kind of configuration into my database. This works well: This is my class:

public class Configuration : IConfiguration {.... public ICollection<EmailClassificationPattern> emailClassificationPatterns { get; set; } ... }

I get two tables dbo.Configurations and dbo.EmailClassificationPatterns. dbo.EmailClassificationPatterns has 4 entries and each references correctly to dbo.Configurations via a field called Configuration_ID.

I am loading the configuration this way:

var configuration = (Configuration)mycontext.Configurations.Where(x => x.configurationName=="Default").FirstOrDefault();

Then I am trying to access the member emailClassificationPatterns this was:

 var relevantSubjectList = configuration.emailClassificationPatterns. Select( x => x.subjectPatternForMailCollection);

But I get a ReferenceNullException because emailClassificationPatterns is NULL. Why does enttity framework not load the referenced members? I don't have the possibility to include the referenced member as IntelliSense doesn't provide .Inlcude() (like this:)

var configuration = (Configuration)mycontext.Configurations.Where(x => x.configurationName=="Default").Include("emailClassificationPattern")

Do I HAVE to enable eagerLoading? If yes - how? Is there another way to access referenced members and is there some kind of best-practice?

Best regards

Sebastian

Youp Bernoulli · Accepted Answer · 2014-10-01 15:30:21Z

1

The Include statement comes before Where. This will load "child" entities. Like so:

var configuration = Configuration)mycontext.Configurations.Include("emailClassificationPattern").Where(x => x.configurationName=="Default")

answered Oct 1, 2014 at 15:30

Youp Bernoulli

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3 Comments

sebastian87 Over a year ago

Is there another possibility where I don't explicitly have to specify which Child-Memeber-Class should also be loaded? I would have expected that EF recognizes which child-members are needed (based on the code) and loads these element dynamically...

Youp Bernoulli Over a year ago

Nope. You have to explicitly load them. his is also pretty smart because in huge relational databases there can be tons of related child-(child-child-etc.)-entities.

Youp Bernoulli Over a year ago

But...what you can also do is just load the configuration entities and when you Enumerate certain child entities of Configuration these will be loaded on demand (just-in-time) if I remember it right. Google is your friend! Lots of documentation about (eager)loading in EF ;)

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