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EF How to query more entities with .include() and using repository pattern

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?

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);

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.

Multiple Include and Where Clauses Linq

I have a database where I'm wanting to return a list of Clients.
These clients have a list of FamilyNames.
I started with this
var query = DbContext.Clients.Include(c => c.FamilyNames).ToList() //returns all clients, including their FamilyNames...Great.
But I want somebody to be able to search for a FamilyName, ifany results are returned, then show the clients to the user.
so I did this...
var query = DbContext.Clients.Include(c => c.FamilyNames.Where(fn => fn.familyName == textEnteredByUser)).ToList();
I tried...
var query = DbContext.Clients.Include(c => c.FamilyNames.Any(fn => fn.familyName == textEnteredByUser)).ToList();
and...
var query = DbContext.FamilyNames.Include(c => c.Clients).where(fn => fn.familyname == textEnteredByUser.Select(c => c.Clients)).ToList();
What I would like to know (obviously!) is how I could get this to work, but I would like it if at all possible to be done in one query to the database. Even if somebody can point me in the correct direction.
Kind regards

In Linq to Entities you can navigate on properties and they will be transformed to join statements.
This will return a list of clients.
var query = DbContext.Clients.Where(c => c.FamilyNames.Any(fn => fn == textEnteredByUser)).ToList();
If you want to include all their family names with eager loading, this should work:
var query = DbContext.Clients.Where(c => c.FamilyNames.Any(fn => fn == textEnteredByUser)).Include(c => c.FamilyNames).ToList();
Here is some reference about loading related entities if something doesn't work as expected.

You can use 'Projection', basically you select just the fields you want from any level into a new object, possibly anonymous.
var query = DbContext.Clients
.Where(c => c.FamilyNames.Any(fn => fn == textEnteredByUser))
// only calls that can be converted to SQL safely here
.Select(c => new {
ClientName = c.Name,
FamilyNames = c.FamilyNames
})
// force the query to be materialized so we can safely do other transforms
.ToList()
// convert the anon class to what we need
.Select(anon => new ClientViewModel() {
ClientName = anon.ClientName,
// convert IEnumerable<string> to List<string>
FamilyNames = anon.FamilyNames.ToList()
});
That creates an anonymous class with just those two properties, then forces the query to run, then performs a 2nd projection into a ViewModel class.
Usually I would be selecting into a ViewModel for passing to the UI, limiting it to just the bare minimum number of fields that the UI needs. Your needs may vary.

LINQ to EF returning all fields not just those in Select()

This is the gist of my query which I'm testing in LinqPad using Linq to Entity Framework.
In my mind the resultant SQL should begin with something like SELECT TableA.ID AS myID. Instead, the SELECT includes all fields from all of the tables. Needless to say this incurs a massive performance hit among other problems. How can I prevent this?
var AnswerList = this.Answers
.Where(x=>
..... various conditions on x and related entities...
)
.GroupBy(x => new {x.TableA,x.TableB,x.TableC})
.Select(g=>new {
myID = g.Key.TableA.ID,
})
AnswerList.Dump();
In practice I'm using a new type instead of an anonymous one but the results are the same either way.
Let me know if you need me to fill in more of the ...'s.
UPDATE
I've noticed I can prevent this problem by explicitly specifying the fields I want returned in the GroupBy method, e.g. new {x.TableA.ID ... }
But I still don't understand why it doesn't work just using the Select method (which DOES work when doing the equivalent in Linq to SQL).

Hi,
Could you please try below....?
var query = from SubCat in mySubCategory
where SubCat.CategoryID == 1
group 1 by SubCat.CategoryID into grouped
select new { Catg = grouped.Key,
Count = grouped.Count() };
Thank you,
Vishal Patel

LINQ Query - Only get Order and MAX Date from Child Collection

I'm trying to get a list that displays 2 values in a label from a parent and child (1-*) entity collection model.
I have 3 entities:
[Customer]: CustomerId, Name, Address, ...
[Order]: OrderId, OrderDate, EmployeeId, Total, ...
[OrderStatus]: OrderStatusId, StatusLevel, StatusDate, ...
A Customer can have MANY Order, which in turn an Order can have MANY OrderStatus, i.e.
[Customer] 1--* [Order] 1--* [OrderStatus]
Given a CustomerId, I want to get all of the Orders (just OrderId) and the LATEST (MAX?) OrderStatus.StatusDate for that Order.
I've tried a couple of attempts, but can seem to get the results I want.
private IQueryable<Customer> GetOrderData(string customerId)
{
var ordersWithLatestStatusDate = Context.Customers
// Note: I am not sure if I should add the .Expand() extension methods here for the other two entity collections since I want these queries to be as performant as possible and since I am projecting below (only need to display 2 fields for each record in the IQueryable<T>, but thinking I should now after some contemplation.
.Where(x => x.CustomerId == SelectedCustomer.CustomerId)
.Select(x => new Custom
{
CustomerId = x.CustomerId,
...
// I would like to project my Child and GrandChild Collections, i.e. Orders and OrderStatuses here but don't know how to do that. I learned that by projecting, one does not need to "Include/Expand" these extension methods.
});
return ordersWithLatestStatusDate ;
}
---- UPDATE 1 ----
After the great solution from User: lazyberezovsky, I tried the following:
var query = Context.Customers
.Where(c => c.CustomerId == SelectedCustomer.CustomerId)
.Select(o => new Customer
{
Name = c.Name,
LatestOrderDate = o.OrderStatus.Max(s => s.StatusDate)
});
In my hastiness from my initial posting, I didn't paste everything in correctly since it was mostly from memory and didn't have the exact code for reference at the time. My method is a strongly-typed IQueryabled where I need it to return a collection of items of type T due to a constraint within a rigid API that I have to go through that has an IQueryable query as one of its parameters. I am aware I can add other entities/attributes by either using the extension methods .Expand() and/or .Select(). One will notice that my latest UPDATED query above has an added "new Customer" within the .Select() where it was once anonymous. I'm positive that is why the query failed b/c it couldn't be turn into a valid Uri due to LatestOrderDate not being a property of Customer at the Server level. FYI, upon seeing the first answer below, I had added that property to my client-side Customer class with simple { get; set; }. So given this, can I somehow still have a Customer collection with the only bringing back those 2 fields from 2 different entities? The solution below looked so promising and ingenious!
---- END UPDATE 1 ----
FYI, the technologies I'm using are OData (WCF), Silverlight, C#.
Any tips/links will be appreciated.

This will give you list of { OrderId, LatestDate } objects
var query = Context.Customers
.Where(c => c.CustomerId == SelectedCustomer.CustomerId)
.SelectMany(c => c.Orders)
.Select(o => new {
OrderId = o.OrderId,
LatestDate = o.Statuses.Max(s => s.StatusDate) });
.
UPDATE construct objects in-memory
var query = Context.Customers
.Where(c => c.CustomerId == SelectedCustomer.CustomerId)
.SelectMany(c => c.Orders)
.AsEnumerable() // goes in-memory
.Select(o => new {
OrderId = o.OrderId,
LatestDate = o.Statuses.Max(s => s.StatusDate) });
Also grouping could help here.

If I read this correctly you want a Customer entity and then a single value computed from its Orders property. Currently this is not supported in OData. OData doesn't support computed values in the queries. So no expressions in the projections, no aggregates and so on.
Unfortunately even with two queries this is currently not possible since OData doesn't support any way of expressing the MAX functionality.
If you have control over the service, you could write a server side function/service operation to execute this kind of query.

Entity Framework and Repository Pattern (problem with IQueryable)

I just switched from Linq 2 SQL to Entity Framework, and I'm seeing some strange behaviors in EF that I'm hoping someone can help with. I tried Googling around, but I wasn't able to find other people with this same problem. I've mocked up a scenario to explain the situation.
If I work directly with an EF context, I'm able to do a select within a select. For example, this executes perfectly fine:
// this is an Entity Framework context that inherits from ObjectContext
var dc = new MyContext();
var companies1 = (from c in dc.Companies
select new {
Company = c,
UserCount = (from u in dc.CompanyUsers
where u.CompanyId == c.Id
select u).Count()
}).ToList();
However, if I use a repository pattern where the repository is returning IQueryable (or even ObjectSet or ObjectQuery), I get a NotSupportedException (LINQ to Entities does not recognize the method 'System.Linq.IQueryable`1)...
Here is an example of my repository:
public class Repository {
private MyContext _dc;
public Repository() {
_dc = new MyContext();
}
public IQueryable<Company> GetCompanies() {
return _dc.Companies;
}
public IQueryable<CompanyUser> GetCompanyUsers() {
return _dc.CompanyUsers;
}
}
// I'm using the repository inside another class (e.g. in my Services layer)
var repository = new Repository();
var companies2 = (from c in repository.GetCompanies()
select new {
Company = c,
UserCount = (from u in repository.GetCompanyUsers()
where u.CompanyId == c.Id
select u).Count()
}).ToList();
The above code throws a NotSupportedException.
I realize that if there's an association between Companies and CompanyUsers, then I can simply do this and it will work fine:
var companies3 = (from c in repository.GetCompanies()
select new {
Company = c,
UserCount = (from u in c.CompanyUsers
select u).Count()
}).ToList();
...but my example is just a simplified version of a more complicated scenario where I don't have an association between the entities.
So I'm very confused why Entity Framework is throwing the NotSupportedException. How is it that the query works perfectly fine when I'm working with the EF context directly, but it's not supported if I'm working with IQueryable returned from another method. This worked perfectly fine with Linq 2 SQL, but it doesn't seem to work in Entity Framework.
Any insight would be greatly appreciated.
Thanks in advance.

I suspect that what's happening is that EF sees the expression for repository.GetCompanyUsers() inside the lambda for the first select and doesn't know what to do with it because repository isn't an EF context. I think that if you pass in the IQueryable directly instead of an expression that returns it, it should work.
How about if you do this:
var companyUsers = repository.GetCompanyUsers();
var companies2 = (from c in repository.GetCompanies()
select new {
Company = c,
UserCount = (from u in companyUsers
where u.CompanyId == c.Id
select u).Count()
}).ToList();

This is one of those strange quirks with Linq to SQL/EF. Apparently they implemented a way to translate from a getter property to SQL, but not a way to translate from a getter function to SQL.
If instead of a function GetCompanyUsers() you use a property like CompanyUsers, it should work.
Weird eh?
So instead of
public IQueryable<CompanyUser> GetCompanyUsers() {
return _dc.CompanyUsers;
}
You might do
public IQueryable<CompanyUser> CompanyUsers {
get { return _dc.CompanyUsers; }
}
As far as parameterized queries go (which you can't do with a property, obviously), see my question answered here: Custom function in Entity Framework query sometimes translates properly, sometimes doesn't
You can also have wheres and selects in the property too; they'll translate fine. For instance, if I had a blog with an Articles table that contains some articles that aren't online:
public IQueryable<Article> LiveArticles {
get { return _dc.Articles.Where(a => !a.IsDraft); }
}
That'll also reduce the number of parameterized queries that you need.