Procédure : explorer des relations à l'aide des propriétés de navigation (Entity Framework)
Cette rubrique montre comment explorer des relations au moyen de propriétés de navigation. Pour plus d'informations, voir Propriétés de navigation. L'exemple obtient toutes les commandes des contacts dont le nom est « Zhou ». La propriété de navigation Contact.SalesOrderHeader est utilisée pour obtenir la collection des objets SalesOrderHeader de chaque contact. Le même exemple est repris en utilisant chacune des technologies de requête Entity Framework suivantes :
LINQ to Entities
Entity SQL avec ObjectQuery<T>
Méthodes du Générateur de requêtes d'ObjectQuery<T>
L'exemple de cette rubrique est basé sur le modèle de vente Adventure Works Sales Model. Pour exécuter le code de cette rubrique, vous devez déjà avoir ajouté le modèle de vente AdventureWorks à votre projet et configuré ce dernier pour qu'il utilise Entity Framework. Pour plus d'informations, consultez Procédure : utiliser l'Assistant EDM (Entity Framework) ou Procédure : configurer manuellement un projet Entity Framework et Procédure : définir manuellement un modèle EDM (Entity Data Model) (Entity Framework).
Exemple
Cet exemple utilise LINQ to Entities .
Dim lastName = "Zhou"
Using context As New AdventureWorksEntities
Dim contacts As ObjectSet(Of Contact) = context.Contacts
Dim ordersQuery = From contact In contacts _
Where contact.LastName = lastName _
Select New With _
{.LastName = contact.LastName, _
.Orders = contact.SalesOrderHeaders}
For Each order In ordersQuery
Console.WriteLine("Name: {0}", order.LastName)
For Each orderInfo In order.Orders
Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}", _
orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue)
Next
Console.WriteLine("")
Next
End Using
string lastName = "Zhou";
using (AdventureWorksEntities context = new AdventureWorksEntities())
{
ObjectSet<Contact> contacts = context.Contacts;
var ordersQuery = from contact in contacts
where contact.LastName == lastName
select new { LastName = contact.LastName, Orders = contact.SalesOrderHeaders };
foreach (var order in ordersQuery)
{
Console.WriteLine("Name: {0}", order.LastName);
foreach (SalesOrderHeader orderInfo in order.Orders)
{
Console.WriteLine("Order ID: {0}, Order date: {1}, Total Due: {2}",
orderInfo.SalesOrderID, orderInfo.OrderDate, orderInfo.TotalDue);
}
Console.WriteLine("");
}
}
Cet exemple utilise Entity SQL .
Using context As New AdventureWorksEntities()
Dim esqlQuery As String = "SELECT c.FirstName, c.SalesOrderHeaders " & _
" FROM AdventureWorksEntities.Contacts AS c where c.LastName = @ln"
Dim query As New ObjectQuery(Of DbDataRecord)(esqlQuery, context)
' Add parameters to the collection.
query.Parameters.Add(New ObjectParameter("ln", "Zhou"))
For Each rec As DbDataRecord In query
' Display contact's first name.
Console.WriteLine("First Name {0}: ", rec(0))
Dim list As List(Of SalesOrderHeader) = TryCast(rec(1), List(Of SalesOrderHeader))
' Display SalesOrderHeader information
' associated with the contact.
For Each soh As SalesOrderHeader In list
Console.WriteLine(" Order ID: {0}, Order date: {1}, Total Due: {2}",
soh.SalesOrderID, soh.OrderDate, soh.TotalDue)
Next
Next
End Using
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
string esqlQuery = @"SELECT c.FirstName, c.SalesOrderHeaders
FROM AdventureWorksEntities.Contacts AS c where c.LastName = @ln";
ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(esqlQuery, context);
query.Parameters.Add(new ObjectParameter("ln", "Zhou"));
foreach (DbDataRecord rec in query)
{
// Display contact's first name.
Console.WriteLine("First Name {0}: ", rec[0]);
List<SalesOrderHeader> list = rec[1] as List<SalesOrderHeader>;
// Display SalesOrderHeader information
// associated with the contact.
foreach (SalesOrderHeader soh in list)
{
Console.WriteLine(" Order ID: {0}, Order date: {1}, Total Due: {2}",
soh.SalesOrderID, soh.OrderDate, soh.TotalDue);
}
}
}
Cet exemple utilise la méthode du Générateur de requêtes.
Dim lastName = "Zhou"
Using context As New AdventureWorksEntities()
' Define a query that returns a nested
' DbDataRecord for the projection.
Dim query As ObjectQuery(Of DbDataRecord) = context.Contacts.Select("it.FirstName, it.LastName, it.SalesOrderHeaders") _
.Where("it.LastName = @ln", New ObjectParameter("ln", lastName))
For Each rec As DbDataRecord In query.Execute(MergeOption.AppendOnly)
' Display contact's first name.
Console.WriteLine("First Name {0}: ", rec(0))
Dim list As List(Of SalesOrderHeader) = TryCast(rec(2), List(Of SalesOrderHeader))
' Display SalesOrderHeader information
' associated with the contact.
For Each soh As SalesOrderHeader In list
Console.WriteLine(" Order ID: {0}, Order date: {1}, Total Due: {2}", _
soh.SalesOrderID, soh.OrderDate, soh.TotalDue)
Next
Next
End Using
string lastName = "Zhou";
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
// Define a query that returns a nested
// DbDataRecord for the projection.
ObjectQuery<DbDataRecord> query =
context.Contacts.Select("it.FirstName, "
+ "it.LastName, it.SalesOrderHeaders")
.Where("it.LastName = @ln", new ObjectParameter("ln", lastName));
foreach (DbDataRecord rec in
query.Execute(MergeOption.AppendOnly))
{
// Display contact's first name.
Console.WriteLine("First Name {0}: ", rec[0]);
List<SalesOrderHeader> list = rec[2]
as List<SalesOrderHeader>;
// Display SalesOrderHeader information
// associated with the contact.
foreach (SalesOrderHeader soh in list)
{
Console.WriteLine(" Order ID: {0}, " +
"Order date: {1}, Total Due: {2}",
soh.SalesOrderID, soh.OrderDate, soh.TotalDue);
}
}
}
Voir aussi
Tâches
Concepts
Interrogation d'un modèle conceptuel (Entity Framework)
Définition et gestion des relations (Entity Framework)