Why is EF eager loading include not working as expected?

Question

I have this repository,

public class Repository<TEntity> : IRepository<TEntity> where TEntity : class
{
    private readonly DbContext context;
    private readonly DbSet<TEntity> dbEntitySet;

    public Repository(DbContext context)
    {
        if (context == null)
            throw new ArgumentNullException("context");

        this.context = context;
        this.dbEntitySet = context.Set<TEntity>();
    }

    public IEnumerable<TEntity> GetAll()
    {
        return this.dbEntitySet;
    }

    public IEnumerable<TEntity> GetAll(string include)
    {
        return this.dbEntitySet.Include(include);
    }

    public IEnumerable<TEntity> GetAll(string[] includes)
    {
        foreach (var include in includes)
            this.dbEntitySet.Include(include);

        return this.dbEntitySet;
    }

    public void Create(TEntity model)
    {
        this.dbEntitySet.Add(model);
    }

    public void Update(TEntity model)
    {
        this.context.Entry<TEntity>(model).State = EntityState.Modified;
    }

    public void Remove(TEntity model)
    {
        this.context.Entry<TEntity>(model).State = EntityState.Deleted;
    }

    public void Dispose()
    {
        this.context.Dispose();
    }
}

and the issue I have is with this method:

public IEnumerable<TEntity> GetAll(string[] includes)
{
    foreach (var include in includes)
        this.dbEntitySet.Include(include);

    return this.dbEntitySet;
}

When I run it and put a breakpoint before the return, it is as if the foreach is being ignored.

the method above it works fine:

public IEnumerable<TEntity> GetAll(string include)
{
    return this.dbEntitySet.Include(include);
}

To call it, I basically do this:

var a = this.Repository.GetAll(new string[] { "ForbiddenUsers", "ForbiddenGroups" }).ToList();

which pulls back the results but not does include the includes :D If I modify the call to:

var a = this.Repository.GetAll("ForbiddenUsers").ToList();

It works fine.

Can someone provide me with a resolution?

+1 for the GetAll method idea! Useful! – Stachu Jan 15 '14 at 16:43 — Stachu, Jan 15 '14 at 16:43

luksan · Accepted Answer · 2014-01-16T15:56:47.480

9

Change your method to look like this:

public IEnumerable<TEntity> GetAll(string[] includes)
{
    var query = this.dbEntitySet;

    foreach (var include in includes)
        query = query.Include(include);

    return query;
}

The Include method does not mutate the DbSet, it only returns you a new DbQuery with your include.

edited Jan 16 '14 at 15:56

answered Jan 15 '14 at 16:36

luksan

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For the first one, I get an invalid cast exception, for the second one it errors out when I run it (it compiles fine). I am going to do a few more tests to see what the problem is – r3plica Jan 16 '14 at 10:21
Yeah, the problem with your second method is that you the include thinks I am trying to create a navigation property with all the joined strings which just doesn't work – r3plica Jan 16 '14 at 10:25
Ah, OK. I thought you might be able to do that but I guess I was mistaken. I've removed that second example. – luksan Jan 16 '14 at 15:57

CodeNotFound · Answer 2 · 2014-01-18T11:48:42.560

1

This code is incorrect:

public IEnumerable<TEntity> GetAll(string[] includes)
{
    foreach (var include in includes)
       this.dbEntitySet.Include(include);

    return this.dbEntitySet;
}

The correct code is the following:

public IEnumerable<TEntity> GetAll(string[] includes)
{
     IQueryable<T> query = this.dbEntitySet;

     foreach (var include in includes)
         query = query.Include(include);

    return query;
}

In your place I will use Lambda Expressions like this:

public IEnumerable<TEntity> GetAll(Expression<Func<T, object>>[] includes)
{
     IQueryable<T> query = this.dbEntitySet;

     foreach (var include in includes)
         query = query.Include(include);

     return query;
}

edited Jan 18 '14 at 11:48

answered Jan 15 '14 at 16:40

CodeNotFound

22,153
10
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Lambdas may not work here. `Expression>` is not convertible to `Expression>`, and I believe a cast in the lambda will throw off the magic. – Cory Nelson Jan 15 '14 at 16:43
@CoryNelson I never mentionned Expression>. Expression> work well for me. Where did you see that TRet in my code? – CodeNotFound Jan 15 '14 at 17:11
Indeed you did not mention it -- what I'm pointing out is that everyone's lambdas *will* be of some type -- not `object` -- so I don't see the usefulness of your method as expressions for `Func` etc. are not convertible to expressions for `Func`. – Cory Nelson Jan 15 '14 at 18:52
Did you test my code before talking about that? Maybe it's not work with your scenarios but it works well for me. You can check this example => http://blogs.msdn.com/b/wriju/archive/2013/08/23/using-repository-pattern-in-entity-framework.aspx – CodeNotFound Jan 15 '14 at 19:24
@CodeNotFound your first query has the same problem as mine. It seems to ignore the includes, although it does compile. Also, how would you call the second method?? – r3plica Jan 16 '14 at 10:40
@r3plica If you read my post i said that the firt query is incorrect. The second is the correct. Not forget to use my last query beacuase it uses lambda expressions. – CodeNotFound Jan 16 '14 at 17:00
Hey @CodeNotFound Your second query is incorrect too, it should be query = query.Include(include); – r3plica Jan 18 '14 at 00:14

Why is EF eager loading include not working as expected?

2 Answers2