How to: Query Data

This article is relevant to entity models that utilize the deprecated Visual Studio integration of Telerik Data Access. The current documentation of the Data Access framework is available here.

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
• Filtering Data
• Ordering Data

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:

• LINQ Support