Question

so first my entities

the problem i want to have a page with all the story titles and their types

there are three stories LongStory , CoOpStory, GenericStory

the generic story is associated with StoryType for the type of the generic story

i have two problems

first when i want to check if the story is LongStory or CoOpStory i have to get all the entity and check the entity type if it is LongStory then do something , i don’t know how to retrieve some data [only the title] and check the type

my second problem like i said i want to have a page with all the story titles and their types i don’t know how to do that without making a lot of queries , i can’t make a join to the StoryType table because it must be GenericStory to be associated with that , so what i do first get all the stories then do an extra query for every GenericStory to get the type

Answer 1

You are looking of OfType and Concat extension methods.

To get only LongStory instances you just need to call:

var longStories = context.Stories.OfType<LongStory>().ToList();

To get your bigger query it is little bit more complex. You can either try:

var allStories = context.Stories
                        .OfType<GenericStory>()
                        .Include("StoryType") // I'm not sure how this works with concat
                        .Concat(
                             context.Stories.OfType<LongStory>.Concat(         
                                  context.Stories.OfType<CoOpStory>()));

Or you can do a projection:

var allStories = context.Stories
                        .OfType<GenericStory>()
                        .Select(s => new { s.Title, s.StoryType.Name })
                        .Concat(
                             context.Stories
                                    .OfType<LongStory>
                                    .Select(s => new { s.Title, "LongStory" })
                                    .Concat(         
                                        context.Stories
                                               .OfType<CoOpStory>()
                                               .Select(s => new { s.Title, Type })));