Filtering Navigation Collections - DevForce Community Forum

var customerQuery = mgr.Customers

.Where(c => c.Country == "USA")

.Select(cust => new {

aCustomer = cust,

Orders = cust.Orders.Take(10),

OrderDetails = cust.Orders.Take(10).SelectMany(o => o.OrderDetails)

});

Ok, so the link above answered my question and while cool, it doesn't allow me to use an Include statement for the filtered collection. So I found the DRC topic "Include and fitler related entities" that offers a suggestion for filtering a navigation collection in a single query to the database.

I adapted that example to my model and produced the following:

EXAMPLE 1

//Return Standard Work Type and first 10 WorkTypes
var myquery = _manager.StandardWorkTypes.Where(e => e.StandardWorkTypeID == standardWorkTypeID)
              .Select(swt => new { StandardWorkType = swt, WorkTypes =  swt.WorkTypes.Take(10)});

This works, but I'd like to be able to return a related entity from WorkTypes.  If I'm not worried about filtering the WorkTypes 
collection I'd write the query as follows:
EXAMPLE 2
//Return Standard Work Type and all Work Types and their associated HealthcareOrganization
var query = from entity in _manager.StandardWorkTypes
            where entity.StandardWorkTypeID == standardWorkTypeID
            select entity;
 
 
 
query = query.Include("WorkTypes.HealthcareOrganization");
 
QUESTION 1 - Is there a way to query StandardWorkType, take/filter WorkTypes AND include HealthcareOrganization 
using the syntax from EXAMPLE 1?
 
 
Before discovering the topic above, I had been issuing two queries, 1 for the StandardWorkType entity and 1 for WorkTypes 
entity. This worked, but my ViewModel only exposed the StandardWorkType entity and the grid I'm using was 
bound to {Binding StandardWorkType.WorkTypes}.  So even though I had loaded the data I wanted in a 
separate query, DevForce went back to the database because it was the first time I had accessed the WorkTypes 
navigation property for my entity.  I then discovered the DRC topic "Navigation properties and data retrieval" and set a 
new EntityReferenceStrategy using 
 
DomainModel.StandardWorkType.PropertyMetadata.WorkTypes.ReferenceStrategy = new EntityReferenceStrategy(EntityReferenceLoadStrategy.DoNotLoad, MergeStrategy.PreserveChanges);
This works as expected and is just beautiful.  I also get the same results if I use 
 
DomainModel.StandardWorkType.PropertyMetadata.WorkTypes.GetEntityReference(standardWorkType).IsLoaded = true;
 
QUESTION 2 - Do you see any red flags here?   If I want to set the EntityReferenceStrategy application wide using 
the first method, should I do that on application startup?  The ERS is app wide across all Entity Mangers, right?
 
 
Thanks for your help.

Edited by gshelton - 21-Apr-2011 at 5:01pm