Entity Framework Core: load related data after object is queried

Question

It is clear how to query an entity and include all the related data; e.g.:

using (var context = new BloggingContext())
{
    var blogs = context.Blogs
        .Include(blog => blog.Posts)
        .Include(blog => blog.Owner)
        .ToList();
}

REF

My question is, given an entity that is missing some related data, how I can ask EF to fetch its related data from DB?

For instance:

var blog = context.Blogs.Find(1); // get the blog with ID=1

// how can I do something like:
blog.Include(x => x.Posts);

@GertArnold Your link to the documentation for explicit loading is the correct answer to this question. You should re-submit it as an Answer rather than as a Comment. — Dan Kroymann
– Dan Kroymann, Commented Jan 25, 2020 at 17:55

Dr. Strangelove · Accepted Answer · 2020-01-28 07:11:30Z

7

context.Entry(blog).Collection(x => x.Posts).Load();
context.Entry(blog).Reference(x => x.Owner).Load();

According to this reference, as suggested by @GertArnold

answered Jan 28, 2020 at 7:11

Dr. Strangelove

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Comments

Hamed Moghadasi · Accepted Answer · 2020-01-25 16:24:44Z

3

As microsoft said, the retun dataType of Find() method is TEntity.

public virtual TEntity Find (params object[] keyValues);

and It means that Find() method hit the database and will fetch a TEntity. So you can't extend your query after Find() method. hence, If you wanna get related data in this query you must call Include() before any method which hit the database. as like as below query:

var blog = context.Blogs.Include(x => x.Posts).SingleOrDefault(x => x.Id == 1);

As a conclusion, The way that you expected to do with Includ() is not possible, but if you have to do this as @GertArnold said in comment, you can follow this way.

good luck.

edited Jan 25, 2020 at 16:24

answered Jan 25, 2020 at 16:16

Hamed Moghadasi

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Comments

Meysam · Accepted Answer · 2020-01-25 07:39:01Z

-2

try to use this

var blog = context.Blogs.Include(x => x.Posts).FirstOrDefault(x => x.Id == 1);

answered Jan 25, 2020 at 7:39

Meysam

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3 Comments

Dr. Strangelove Over a year ago

Maybe the question was not clear, I mean, I don't want to use Blogs anymore, for application reasons.

Meysam Over a year ago

it was I suppose. why don't you query from "Posts" DbSet directly? something like this context.Posts.FirstOrDefault(x => x.BlogId== 1);

Ramil Aliyev 007 Over a year ago

It is eager loading. To solve this problem need explicit loading

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