/// <summary>
/// Eager loading done properly
/// With explicit join, server filtering and projection
/// </summary>
public static void QuerySix()
{
using (var dbContext = new AdventureWorks2014Entities())
{
Console.WriteLine("Enter last name to search email addresses: ");
var lastName = Console.ReadLine();
var emails = from person in dbContext.People
join emailAddress in dbContext.EmailAddresses
on person.BusinessEntityID equals emailAddress.BusinessEntityID
where person.LastName == lastName
select emailAddress.EmailAddress1;
//var emails = dbContext.People
// .Where(x => x.LastName == lastName)
// .SelectMany(x => x.EmailAddresses)
// .Select(x => x.EmailAddress1);
//var emails =
// dbContext.People
// .Where(x => x.LastName == lastName)
// .Join(dbContext.EmailAddresses,
// l => l.BusinessEntityID,
// r => r.BusinessEntityID,
// (l, r) => r.EmailAddress1);
foreach (var email in emails)
{
Console.WriteLine(email);
}
}
}
/// <summary>
/// Eager loading the email addresses in one server request
/// SET Based operation
/// </summary>
public static void QueryFive()
{
using (var dbContext = new AdventureWorks2014Entities())
{
Console.WriteLine("Enter last name to search email addresses: ");
var lastName = Console.ReadLine();
var people = dbContext.People
.Include(x => x.EmailAddresses)
.Where(x => x.LastName == lastName)
.Select(x => x);
//var people = from person in dbContext.People.Include(x => x.EmailAddresses)
// where person.LastName == lastName
// select person;
foreach (var person in people)
{
foreach (var email in person.EmailAddresses)
{
Console.WriteLine(email.EmailAddress1);
}
}
}
}
/// <summary>
/// Using a projection to retrieve less data as possible from the server
/// </summary>
public static void QueryThree()
{
using (var dbContext = new AdventureWorks2014Entities())
{
Console.WriteLine("Enter last name to search: ");
var lastName = Console.ReadLine();
var peopleBusinessEntityIDs = dbContext.People
.Where(x => x.LastName == lastName)
.Select(x => x.BusinessEntityID);
foreach (var businessEntityID in peopleBusinessEntityIDs)
{
Console.WriteLine(businessEntityID);
}
}
}
public static void QueryOne()
{
using (var dbContext = new AdventureWorks2014Entities())
{
Console.WriteLine("Enter last name to search: ");
var lastName = Console.ReadLine();
var people = dbContext.People.Select(x => x);
foreach (var person in people)
{
if (person.LastName == lastName)
{
Console.WriteLine(person.BusinessEntityID);
}
}
}
}