EF. How to include only some sub results in a model?

问题

I'm trying to select list of Users and for each User JobTitle in correct language depended of strLang selected by user.

Something like that:

IList<User> myData;
myData = Context.Users.Where(u => u.Location == strLocation)
                .Include(u => u.JobTitles.Where(e => e.Language == strLang))
                    .ToList();

But it seems Include doesn't like Where clause

回答1:

You can't conditionally include only a few entities of a related collection, so you should use projection to get the stuff you need:

IList<User> myData;
var temp = Context.Users.Where(u => u.Location == strLocation)
      .Select(u => new
      {
        User = u;
        Locations = u.JobTitles.Where(e => e.Language == strLang));
      });

foreach(var t in temp)
{
   User user = t.User;
   user.Locations = t.Locations;
   myData.Add(user);
}

回答2:

You cannot do it by using the "Include" method since it only take naviation properties.

Disclaimer: I'm the owner of the project EF+ on github.

EF+ Query IncludeFilter allow you to easily filter related entities:

// using Z.EntityFramework.Plus; // Don't forget to include this.    
IList<User> myData;
    myData = Context.Users.Where(u => u.Location == strLocation)
                    .IncludeFilter(u => u.JobTitles.Where(e => e.Language == strLang))
                        .ToList();

You can find the project here

You can find the documentation here

Behind the code, IncludeFilter do exactly like Alexander answer by using a projection.

来源：https://stackoverflow.com/questions/34963319/ef-how-to-include-only-some-sub-results-in-a-model