对ef实体使用（linq？）

Question

I have a fairly complex sql statement with joins. Here is my code using EF:

var MicrositeResponseAdors = _context.MicrositeResponseAdor
    .Include(user => user.UserTracking)
        .ThenInclude(tracking => tracking.AddTradeIn)
    .Include(user => user.UserTracking)
        .ThenInclude(tracking => tracking.TrackingFinance)
    .Include(user => user.UserTracking)
        .ThenInclude(tracking => tracking.SearchTracking)
    .Include(user => user.UserTracking)
        .ThenInclude(tracking => tracking.TrackingType)
    .Include(user => user.UserTracking)
        .ThenInclude(tracking => tracking.Vehicle)
    .FirstOrDefault(m => m.Id == id && m.FirstName.ToLower() != "test" && m.LastName.ToLower() != "test");

I need to add another join to a table that has no primary key, which Entity Framework doesn't allow. I wasn't even able to fake it. So I was told to make something more custom using what I believe is called LINQ?

I cannot figure out how to assign my data values with the original EF entity classes. Here is what I have so far:

var MicrositeResponseAdors = (from p in _context.MicrositeResponseAdor
    join c in _context.UserTracking on p.Id equals c.UserTrackingId
    into pc
    select new {
        MicrositeResponseAdor = p, MicrositeResponseAdor.UserTracking = pc 
    }
).FirstOrDefault();

This gives:

Invalid anonymous type member declarator.

I think that is because of the first part of MicrositeResponseAdor.UserTracking. I am not sure how to assign UserTracking under the MicrositeResponseAdor.

Answer 1

The error you've given is a C# compilation error, as you're trying to name a property MicrositeResponseAdor.UserTracking . Property names can't contain dots.

This would at least compile:

var micrositeResponseAdor = (
    from p in _context.MicrositeResponseAdor
    join c in _context.UserTracking on p.Id equals c.UserTrackingId into pc
    select new {
        MicrositeResponseAdor = p,
        UserTracking = pc 
    }
).FirstOrDefault();

This will make your UserTracking appear in two places:

1. micrositeResponseAdor.UserTracking
2. micrositeResponseAdor.MicrositeResponseAdor.UserTracking

It's in the first because you've put it there, and it's in the second because there's a relationship between the entities anyway, so EF is conveniently populating it if it has loaded it in that context (and it has, because you asked for it explicitly).

So you don't have to assign loaded navigational properties in your query, you just have to make sure the related entities are loaded, either with a manual join, an Include or even a second query.

The question is why you do this at all. You've already had the Include version. The join variant is just more verbose, but it doesn't add anything.

Not that EF will always have a key on every entity, whether the database thinks it is one or not. Technically, that's unrelated Include vs join though.