EF如何使用.include（）和使用存储库模式查询更多实体

Question

I got the following sql statement that I want to implement with entity framework with linq (lambda expression). Here is the SQL:

select *
from tbl_ExampleStoneCatalog 
join tbl_ExampleStoneCategory 
on tbl_ExampleStoneCatalog.fk_ESC = tbl_ExampleStoneCategory.pk_ESC 
join tbl_ExampleStones
on tbl_ExampleStoneCatalog.fk_ES = tbl_ExampleStones.pk_ES
join tbl_ExampleReviewStoneCatalog 
on tbl_ExampleStones.pk_ES = tbl_ExampleReviewStoneCatalog.fk_ES
where .fk_StoneCategory = '%someParameter%'

I tried to use the .include() which brings me to this:

var res = (await this._exampleStoneCatalog.Query()
          .include(esc => esc.ExampleStoneCategory)
          .include(es => es.ExampleStones)
          .include(es => es.ExampleStones.ExampleReviewStoneCatalog))
          .Where(w => w.ExampleStones.ExampleReviewStoneCatalog.Any(
           a => a.StoneCategoryID.Equals(%someParameter%)));

Unfortunately the code stated above won't deliver me the desired result. Furthermore there is a nested Where condition in it => ExampleStones.ExampleReviewStoneCatalog.StoneCategoryID . From what I understand after some research is, that this is not solvable easily with .include().

Is there other ways to filter in nested queries using the lambda expression?

Answer 1

If seems like a many-to-many relationship. I always find it easiest to begin with the connecting table here.

var res = _tbl_B.Repository.Where(b => b.c.Value == "whatever" && b.a.Value == "whatever").Select(b => b.a);

Answer 2

I have found a work around for this problem. The main challenge here is to filter in a nested SQL query. I could not find a solution with .include(). Especially my current work environment in which we are useing repository pattern wouldn't allow me to filter within includes like:

var res = await this._exampleStoneCatalog.Query().include(x => x.ExampleStones.ExampleReviewStoneCatalog.Where(w => w.StoneCategoryID.Equals(%SomeParameter%))).SelectAsync();

Hence I come to the following solution with using linq to sql.

My solution:

 var exampleStoneCatalogEnum = await this._exampleStoneCatalog.Query().SelectAsync();
 var exampleStoneCategoryEnum = await this._exampleStoneCategoryRepository.Query().SelectAsync();
 var exampleStonesEnum = await this.exampleStonesRepository.Query().SelectAsync();
 var exampleReviewStoneCatalogEnum = await this.exampleReviewStoneCatalogRepository.Query().SelectAsync();

 var result = from exampleStoneCatalog in exampleStoneCatalogEnum
              join exampleStoneCategory in exampleStoneCategoryEnum on exampleStoneCatalog.Id equals exampleStoneCategory.Id
              join exampleStones in exampleStonesEnum on exampleStoneCatalog.Id equals exampleStones.Id
              join exampleReviewStoneCatalog in exampleReviewStoneCatalogEnum on exampleStones.Id equals exampleReviewStoneCatalog.Id
              where exampleReviewStoneCatalog.StoneCategoryID.Equals(revCategory)
              select exampleStoneCatalog;
 return result;

as you can see I first get the required data of each table and join them in my result including the where condition in the end. This returns the desired result.