Which code segment should you use?

You use Microsoft Visual Studio 2010 and Microsoft Entity Framework 4.0 to create an application.
The application connects to a Microsoft SQL Server database. You use the ADO.NET LINQ to SQL
model to retrieve data from the database. The applications contains the Category and Product
entities as shown in the following exhibit:

You need to ensure that LINO to SQL executes only a single SQL statement against the database. You
also need to ensure that the query returns the list of categories and the list of products. Which code
segment should you use?

A.
using (NorthwindDataContext dc = new NorthwindDataContext()) {
dc.ObjectTrackingEnabled = false;
var categories = from c in dc.Categories

select c;
foreach (var category in categories) {
Console.WriteLine(“{0} has {1} products”, category.CategoryName, category.Products.Count);
}
}

B.
using (NorthwindDataContext dc = new NorthwindDataContext()) {
dc.DeferredLoadingEnabled = false;
DataLoadOptions dlOptions = new DataLoadOptions();
dlOptions.LoadWith<Category>(c => c.Products);
dc.LoadOptions = dlOptions;
var categories = from c in dc.Categories
select c;
foreach (var category in categories) {
Console.WriteLine(“{0} has {1} products”, category.CategoryName, category.Products.Count);
}
}

C.
using (NorthwindDataContext dc = new NorthwindDataContext()) {
dc.DeferredLoadingEnabled = false;
var categories = from c in dc.Categories
select c;
foreach (var category in categories) {
Console.WriteLine(“{0} has {1} products”, category.CategoryName, category.Products.Count);
}
}

D.
using (NorthwindDataContext dc = new NorthwindDataContext()) {
dc.DeferredLoadingEnabled = false;
DataLoadOptions dlOptions = new DataLoadOptions();
dlOptions.AssociateWith<Category>(c => c.Products);
dc.LoadOptions = dlOptions;
var categories = from c in dc.Categories
select c;
foreach (var category in categories) {
Console.WriteLine(“{0} has {1} products”, category.CategoryName, category.Products.Count);
}
}

Explanation:
DataLoadOptions Class Provides for immediate loading and filtering of related
data. DataLoadOptions.LoadWith(LambdaExpression) Retrieves specified data related to the main
target by using a lambda expression.
You can retrieve many objects in one query by using
LoadWith.
DataLoadOptions.AssociateWith(LambdaExpression) Filters the objects retrieved for a particular
relationship.
Use the AssociateWith method to specify sub-queries to

limit the amount of retrieved data.
DataLoadOptions Class
(http://msdn.microsoft.com/en-us/library/system.data.linq.dataloadoptions.aspx)
How to: Retrieve Many Objects At Once (LINQ to SQL)
(http://msdn.microsoft.com/en-us/library/Bb386917(v=vs.90).aspx)
How to: Filter Related Data (LINQ to SQL)
(http://msdn.microsoft.com/en-us/library/Bb882678(v=vs.100).aspx)