/// <summary>
/// Demostrates how to use lazy loading for related entities
/// </summary>
static void LazyLoadingTest()
{
Console.WriteLine("---Lazy Loading---");
using (LazyLoadingEntities context = new LazyLoadingEntities())
{
// Query the department entities which Budget is not NULL
var departments = from d in context.Departments
where d.Budget != null
select d;
foreach (var department in departments)
{
Console.WriteLine("Department: {0}", department.Name);
Console.WriteLine("Courses:");
// With Lazy Loading enabled, directly access the
// Courses property of the Department will load the
// related course entities automatically
// Note: here for each department, there will be a
// seperate database call to load the course entities
foreach (var course in department.Courses)
{
Console.WriteLine(course.Title);
}
Console.WriteLine();
}
}
}
/// <summary>
/// Demostrates how to use explicit loading for related entities
/// </summary>
static void ExplicitLoadingTest()
{
Console.WriteLine("---Explicit Loading---");
using (LazyLoadingEntities context = new LazyLoadingEntities())
{
// Lazy loading is enabled dy default in EF4, so turn it off
// to use explicit loading later
context.ContextOptions.LazyLoadingEnabled = false;
// Query the department entities which Budget is not NULL
var departments = from d in context.Departments
where d.Budget != null
select d;
foreach (var department in departments)
{
Console.WriteLine("Department: {0}", department.Name);
Console.WriteLine("Courses:");
// Explicit load the related courses entities if they
// are not loaded yet
// Note: here for each department, there will be a
// seperate database call to load the course entities
if (!department.Courses.IsLoaded)
{
department.Courses.Load();
}
foreach (var course in department.Courses)
{
Console.WriteLine(course.Title);
}
Console.WriteLine();
}
}
}
/// <summary>
/// Demostrates how to use eager loading for related entities
/// </summary>
static void EagerLoadingTest()
{
Console.WriteLine("---Eager Loading---");
using (LazyLoadingEntities context = new LazyLoadingEntities())
{
// Lazy loading is enabled dy default in EF4, so turn it off
// to use eager loading later
context.ContextOptions.LazyLoadingEnabled = false;
// Query the department entities which Budget is not NULL
// Here we use the .Include() method to eager load the related
// course entities
var departments = from d in context.Departments.Include("Courses")
where d.Budget != null
select d;
foreach (var department in departments)
{
Console.WriteLine("Department: {0}", department.Name);
Console.WriteLine("Courses:");
// The related course entities has been already loaded
// Note: for eager loading, there will be only one
// database call to load the department and corresponding
// course entities
foreach (var course in department.Courses)
{
Console.WriteLine(course.Title);
}
Console.WriteLine();
}
}
}
