方法: データ バインディングの動作をカスタマイズする (WCF Data Services)
WCF Data Services では、バインディング コレクションにオブジェクトを追加したとき、バインディング コレクションからオブジェクトを削除したとき、またはプロパティ変更が検出されたときに、DataServiceCollection によって呼び出されるカスタム ロジックを指定できます。 このカスタム ロジックは、Func デリゲートと呼ばれるメソッドとして提供されています。これらは、カスタム メソッドの完了時にも既定の動作を実行する必要がある場合は false を返し、イベントの後続の処理を停止する必要がある場合は true を返します。
このトピックの例は、DataServiceCollection の entityChanged パラメーターと entityCollectionChanged パラメーターの両方のカスタム メソッドを示します。 このトピックの例では、Northwind サンプル データ サービスおよび自動生成されたクライアント データ サービス クラスを使用します。 このサービスおよびクライアント データ クラスは、WCF Data Services クイック スタートを完了したときに作成されます。
例
次の XAML ファイルの分離コード ページは、バインディング コレクションにバインドされたデータへの変更が発生すると呼び出される DataServiceCollection とカスタム メソッドを作成します。 CollectionChanged イベントが発生すると、指定したメソッドは、バインディング コレクションから削除された項目がデータ サービスから削除されることを防止します。 PropertyChanged イベントが発生すると、出荷済みの注文に対する変更がないことを確認するために、ShipDate の値が検証されます。
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());
}
}
}
}
次の XAML は、前の例のウィンドウを定義します。
<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>