Procédure : personnaliser des comportements de liaison de données (WCF Data Services)
Avec Services de données WCF , vous pouvez fournir une logique personnalisée appelée par DataServiceCollection lorsqu'un objet est ajouté ou supprimé de la collection de liaisons ou lorsqu'une modification de propriété est détectée. Cette logique personnalisée est fournie sous la forme de méthodes, référencée comme délégués Func qui retournent une valeur false lorsque le comportement par défaut doit être effectué une fois que la méthode personnalisée est terminée, et true lorsque le traitement suivant de l'événement doit être arrêté.
Les exemples dans cette rubrique fournissent des méthodes personnalisées pour les paramètres entityCollectionChanged et entityChanged de DataServiceCollection. Les exemples dans cette rubrique utilisent l'exemple de service de données Northwind et des classes de service de données client générées automatiquement. Ce service et les classes de données clientes sont créés lorsque vous complétez le démarrage rapide WCF Data Services.
Exemple
La page code-behind suivante du fichier XAML crée une DataServiceCollection avec des méthodes personnalisées appelées lorsque des modifications sont apportées aux données liées à la collection de liaisons. Lorsque l'événement CollectionChanged se produit, la méthode fournie empêche un élément ayant été supprimé de la collection de liaisons d'être supprimé du service de données. Lorsque l'événement PropertyChanged se produit, la valeur ShipDate est validée pour vérifier que les modifications ne sont pas apportées aux ordres déjà livrés.
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data
Imports System.Windows.Documents
Imports System.Windows.Input
Imports System.Windows.Media
Imports System.Windows.Media.Imaging
Imports System.Windows.Navigation
Imports System.Windows.Shapes
Imports System.Data.Services.Client
Imports NorthwindClient.Northwind
Imports System.Collections.Specialized
Partial Public Class CustomerOrdersCustom
Inherits Window
Private context As NorthwindEntities
Private trackedCustomers As DataServiceCollection(Of Customer)
Private Const customerCountry As String = "Germany"
Private Const svcUri As String = "https://localhost:12345/Northwind.svc/"
Private Sub Window_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
Try
' Initialize the context for the data service.
context = New NorthwindEntities(New Uri(svcUri))
' Create a LINQ query that returns customers with related orders.
Dim customerQuery = From cust In context.Customers.Expand("Orders") _
Where cust.Country = customerCountry _
Select cust
' Create a new collection for binding based on the LINQ query.
trackedCustomers = New DataServiceCollection(Of Customer)(customerQuery, _
TrackingMode.AutoChangeTracking, "Customers", _
AddressOf OnMyPropertyChanged, AddressOf OnMyCollectionChanged)
' Bind the root StackPanel element to the collection
' related object binding paths are defined in the XAML.
Me.LayoutRoot.DataContext = trackedCustomers
Catch ex As DataServiceQueryException
MessageBox.Show("The query could not be completed:\n" + ex.ToString())
Catch ex As InvalidOperationException
MessageBox.Show("The following error occurred:\n" + ex.ToString())
End Try
End Sub
' Method that is called when the CollectionChanged event is handled.
Private Function OnMyCollectionChanged( _
ByVal entityCollectionChangedinfo As EntityCollectionChangedParams) As Boolean
If entityCollectionChangedinfo.Action = _
NotifyCollectionChangedAction.Remove Then
' Delete the related items when an order is deleted.
If entityCollectionChangedinfo.TargetEntity.GetType() Is GetType(Order) Then
' Get the context and object from the supplied parameter.
Dim context = entityCollectionChangedinfo.Context
Dim deletedOrder As Order = _
CType(entityCollectionChangedinfo.TargetEntity, Order)
If deletedOrder.Order_Details.Count = 0 Then
' Load the related OrderDetails.
context.LoadProperty(deletedOrder, "Order_Details")
End If
' Delete the order and its related items
For Each item As Order_Detail In deletedOrder.Order_Details
context.DeleteObject(item)
Next
' Delete the order and then return false since the object is already deleted.
context.DeleteObject(deletedOrder)
Return True
Else
Return False
End If
Else
' Use the default behavior.
Return False
End If
End Function
' Method that is called when the PropertyChanged event is handled.
Private Function OnMyPropertyChanged( _
ByVal entityChangedInfo As EntityChangedParams) As Boolean
' Validate a changed order to ensure that changes are not made
' after the order ships.
If entityChangedInfo.Entity.GetType() Is GetType(Order) AndAlso _
(CType(entityChangedInfo.Entity, Order).ShippedDate < DateTime.Today) Then
Throw New ApplicationException(String.Format( _
"The order {0} cannot be changed because it shipped on {1}.", _
CType(entityChangedInfo.Entity, Order).OrderID, _
CType(entityChangedInfo.Entity, Order).ShippedDate))
Return False
Else
Return True
End If
End Function
Private Sub deleteButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
' Get the Orders binding collection.
If customerIDComboBox.SelectedItem IsNot Nothing Then
Dim trackedOrders As DataServiceCollection(Of Order) = _
(CType(customerIDComboBox.SelectedItem, Customer)).Orders
' Remove the currently selected order.
trackedOrders.Remove(CType(ordersDataGrid.SelectedItem, Order))
End If
End Sub
Private Sub saveChangesButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
Try
' Save changes to the data service.
context.SaveChanges()
Catch ex As Exception
MessageBox.Show(ex.ToString())
End Try
End Sub
End Class
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Data.Services.Client;
using NorthwindClient.Northwind;
using System.Collections.Specialized;
namespace NorthwindClient
{
public partial class CustomerOrdersCustom : Window
{
private NorthwindEntities context;
private DataServiceCollection<Customer> trackedCustomers;
private const string customerCountry = "Germany";
private const string svcUri = "https://localhost:12345/Northwind.svc/";
public CustomerOrdersCustom()
{
InitializeComponent();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
try
{
// Initialize the context for the data service.
context = new NorthwindEntities(new Uri(svcUri));
// Create a LINQ query that returns customers with related orders.
var customerQuery = from cust in context.Customers.Expand("Orders")
where cust.Country == customerCountry
select cust;
// Create a new collection for binding based on the LINQ query.
trackedCustomers = new DataServiceCollection<Customer>(customerQuery,
TrackingMode.AutoChangeTracking,"Customers",
OnPropertyChanged, OnCollectionChanged);
// Bind the root StackPanel element to the collection;
// related object binding paths are defined in the XAML.
this.LayoutRoot.DataContext = trackedCustomers;
}
catch (DataServiceQueryException ex)
{
MessageBox.Show("The query could not be completed:\n" + ex.ToString());
}
catch (InvalidOperationException ex)
{
MessageBox.Show("The following error occurred:\n" + ex.ToString());
}
}
// Method that is called when the CollectionChanged event is handled.
private bool OnCollectionChanged(
EntityCollectionChangedParams entityCollectionChangedinfo)
{
if (entityCollectionChangedinfo.Action ==
NotifyCollectionChangedAction.Remove)
{
// Delete the related items when an order is deleted.
if (entityCollectionChangedinfo.TargetEntity.GetType() == typeof(Order))
{
// Get the context and object from the supplied parameter.
DataServiceContext context = entityCollectionChangedinfo.Context;
Order deletedOrder = entityCollectionChangedinfo.TargetEntity as Order;
if (deletedOrder.Order_Details.Count == 0)
{
// Load the related OrderDetails.
context.LoadProperty(deletedOrder, "Order_Details");
}
// Delete the order and its related items;
foreach (Order_Detail item in deletedOrder.Order_Details)
{
context.DeleteObject(item);
}
// Delete the order and then return true since the object is already deleted.
context.DeleteObject(deletedOrder);
return true;
}
else
{
return false;
}
}
else
{
// Use the default behavior.
return false;
}
}
// Method that is called when the PropertyChanged event is handled.
private bool OnPropertyChanged(EntityChangedParams entityChangedInfo)
{
// Validate a changed order to ensure that changes are not made
// after the order ships.
if ((entityChangedInfo.Entity.GetType() == typeof(Order)) &&
((Order)(entityChangedInfo.Entity)).ShippedDate < DateTime.Today)
{
throw new ApplicationException(string.Format(
"The order {0} cannot be changed because it shipped on {1}.",
((Order)(entityChangedInfo.Entity)).OrderID,
((Order)(entityChangedInfo.Entity)).ShippedDate));
}
return false;
}
private void deleteButton_Click(object sender, RoutedEventArgs e)
{
if (customerIDComboBox.SelectedItem != null)
{
// Get the Orders binding collection.
DataServiceCollection<Order> trackedOrders =
((Customer)(customerIDComboBox.SelectedItem)).Orders;
// Remove the currently selected order.
trackedOrders.Remove((Order)(ordersDataGrid.SelectedItem));
}
}
private void saveChangesButton_Click(object sender, RoutedEventArgs e)
{
try
{
// Save changes to the data service.
context.SaveChanges();
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
}
Le code XAML suivant définit la fenêtre de l'exemple précédent.
<Window x:Class="CustomerOrdersCustom"
xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="https://schemas.openxmlformats.org/markup-compatibility/2006"
Height="423" Width="679" Loaded="Window_Loaded" >
<StackPanel Orientation="Vertical" Height="Auto" Name="LayoutRoot" Width="Auto">
<Label Content="Customer ID" Margin="20,0,0,0" />
<ComboBox Name="customerIDComboBox" DisplayMemberPath="CustomerID" ItemsSource="{Binding}"
IsSynchronizedWithCurrentItem="True" SelectedIndex="0" Height="23" Width="120"
HorizontalAlignment="Left" Margin="20,0,0,0" VerticalAlignment="Center" />
<ListView ItemsSource="{Binding Path=Orders}" Name="ordersDataGrid" Margin="34,46,34,50">
<ListView.View>
<GridView AllowsColumnReorder="False" ColumnHeaderToolTip="Line Items">
<GridViewColumn DisplayMemberBinding="{Binding Path=OrderID, Mode=OneWay}"
Header="Order ID" Width="50"/>
<GridViewColumn DisplayMemberBinding="{Binding Path=OrderDate, Mode=TwoWay}"
Header="Order Date" Width="50"/>
<GridViewColumn DisplayMemberBinding="{Binding Path=Freight, Mode=TwoWay}"
Header="Freight Cost" Width="50"/>
</GridView>
</ListView.View>
</ListView>
<StackPanel Orientation="Horizontal">
<Button Name="deleteButton" Content="Delete Order" Click="deleteButton_Click"
Width="80" Height="30" Margin="450,0,10,0"/>
<Button Name="saveChangesButton" Content="Save Changes" Click="saveChangesButton_Click"
Width="80" Height="30" Margin="10,0,0,0"/>
</StackPanel>
</StackPanel>
</Window>