CODEWITHSUNDEEP
entity-framework-coreentity-framework-core-3.0
Miguel Moura
Miguel Moura

Reputation: 39484

Unexpected query exception when using InMemoryDatabase

I have the following EF 3.0 query using InMemoryDatabase:

    IQueryable<Post> posts = _context.Posts.AsNoTracking();

    posts = posts.Where(x => x.Enabled);

    IQueryable<PostModel> models = null;

    try {

     models = jobs
      .Select(x => new PostModel {
        Id = x.Id,
        Enabled = x.Enabled,
        Category = x.Category == null ? null : new CategoryModel {
          Id = x.Category.Id,
          Name = x.Category.Name
        }
      );

      var result = await responses.ToListAsync();

    } catch (Exception e) {

       var ex = e;

    }

Initially posts have 2 items. After the filter Where(x => x.Enabled) I get one item.

But at the end result has no items ... It seems the existing item disappeared in the projection.

Then I tried the following (Removed the Category part):

     models = jobs
      .Select(x => new PostModel {
        Id = x.Id,
        Enabled = x.Enabled
      );

      var result = await responses.ToListAsync();

Now result has one item as expected ...

Any idea what might be wrong? I am really lost on this one.

Upvotes: 0

Views: 53

Answers (1)

Miguel Moura
Miguel Moura

Reputation: 39484

This problem is hard to identify and I am posting the solution which might be useful for others in the future ...

In the Post model configuration Category property / relationship was set as Required.

When I added posts to context one of them had, by mistake, Category set to null.

If I was using SQL Server I would get an error when saving the context.

But because I am doing Testing and I was using InMemoryDatabase the invalid post was accepted.

And that led to the really strange error on the query ...

Conclusion:

In EF 3.0 (and previous versions) the Model is not validated at C# level.
So when using InMemoryDatabase wrong models will be saved and let to unexpected errors in queries.

There is also a Github issue in Entity Framework Core 3.0: https://github.com/aspnet/EntityFrameworkCore/issues/10613

Upvotes: 1

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