How to: Query Data

In this topic, you will learn how to perform basic query operations against the domain model by using Language Integrated Query (LINQ):

Loading Full Entities

The following example shows how to execute a LINQ query that returns a collection of instances of a domain model type.

using ( EntitiesModel dbContext = new EntitiesModel() )
{
   IEnumerable<Category> categories = dbContext.Categories.ToList();
}
Using dbContext As New EntitiesModel()
 Dim categories As IEnumerable(Of Category) = dbContext.Categories.ToList()
End Using

Filtering Data

The following example shows you how to filter which records to be returned from the database.

using ( EntitiesModel dbContext = new EntitiesModel() )
{
   IEnumerable<Category> categories = dbContext.Categories.Where(
       c => c.CategoryName == "SUV" );
}
Using dbContext As New EntitiesModel()
 Dim categories As IEnumerable(Of Category) = dbContext.
  Categories.Where(Function(c) c.CategoryName = "SUV")
End Using

Ordering Data

The following example shows a query that, when executed, retrieves all Car objects. An SQL ORDER BY clause orders the returned objects by Model and Make.

using ( EntitiesModel dbContext = new EntitiesModel() )
{
   List<Car> cars = ( from car in dbContext.Cars
                      orderby car.Model, car.Make
                      select car ).ToList();
}
Using dbContext As New EntitiesModel()
 Dim cars As List(Of Car) = (
  From car In dbContext.Cars
  Order By car.Model, car.Make
  Select car).ToList()
End Using

For further reference: