使用.include提取嵌套对象时，实体框架抛出错误

Question

I have a query here that fetches a single entity object and only one nested entity that meets a specific condition, but I'm receiving an error when executing it.

Here is the query

Profile profile = dbContext.Profiles.Where(i => i.ApplicationUserGuid == guiId)
               .Include(i => i.ProfileImages.Where(k => k.IsMainImage == true)).First();

And here is the exception error message

The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties. Parameter name: path

I also tried running it with another .First(), but still same error message

Profile profile = dbContext.Profiles.Where(i => i.ApplicationUserGuid == guiId)
              .Include(i => i.ProfileImages.Where(k => k.IsMainImage == true).First()).First();

Answer 1

You can't filter related entities inside an Include , you are going to need to project your query with the expected result or use explicit loading :

Profile profile = dbContext.Profiles
                           .Where(i => i.ApplicationUserGuid == guiId)
                           .First();
dbContext.Entry(profile) //Explicit Loading
         .Collection(b => b.ProfileImages) 
         .Query() 
         .Where(k => k.IsMainImage == true).Take(1)
         .Load(); 

If you do the projection it will be only one round trip to your database, and if you use explicit loading it will be two.

Just a FYI, in case you think to project the result, project to an anonymous type or onto a DTO. More info here .