DataServiceCollection<T>.Continuation-Eigenschaft
Ruft ein Fortsetzungsobjekt ab, das verwendet wird, um den nächsten Satz ausgelagerter Ergebnisse zurückzugeben.
Namespace: System.Data.Services.Client
Assembly: Microsoft.Data.Services.Client (in Microsoft.Data.Services.Client.dll)
Syntax
'Declaration
Public Property Continuation As DataServiceQueryContinuation(Of T)
Get
Set
'Usage
Dim instance As DataServiceCollection
Dim value As DataServiceQueryContinuation(Of T)
value = instance.Continuation
instance.Continuation = value
public DataServiceQueryContinuation<T> Continuation { get; set; }
public:
property DataServiceQueryContinuation<T>^ Continuation {
DataServiceQueryContinuation<T>^ get ();
void set (DataServiceQueryContinuation<T>^ value);
}
member Continuation : DataServiceQueryContinuation<'T> with get, set
function get Continuation () : DataServiceQueryContinuation<T>
function set Continuation (value : DataServiceQueryContinuation<T>)
Eigenschaftswert
Typ: System.Data.Services.Client.DataServiceQueryContinuation<T>
Ein DataServiceQueryContinuation<T>-Objekt, das den URI für die Rückgabe des nächsten Satzes ausgelagerter Ergebnisse enthält.
Hinweise
Die Continuation-Eigenschaft gibt einen Link zurück, der verwendet wird, um auf den nächsten Satz ausgelagerter Ergebnisse zuzugreifen, wenn Paging im Datendienst aktiviert ist. Weitere Informationen finden Sie unter Konfigurieren des Datendiensts (WCF Data Services).
Wenn Sie ein ausgelagertes Ergebnis in eine DataServiceCollection<T> laden, müssen Sie Seiten explizit laden, indem Sie die Load(IEnumerable<T>)-Methode auf der DataServiceCollection<T> aufrufen. Hierzu übergeben Sie das Ergebnis der Ausführung des URIs, der aus der Continuation-Eigenschaft abgerufen wurde.
Beispiele
Das folgende Beispiel stammt aus der Code-Behind-Seite für eine XAML (Extensible Application Markup Language)-Seite, die das Fenster SalesOrders in WPF definiert. Wenn das Fenster geladen wird, wird eine DataServiceCollection<T> basierend auf dem Ergebnis einer Abfrage erstellt, die Kunden nach Land gefiltert zurückgibt. Alle Seiten dieses ausgelagerten Ergebnisses werden zusammen mit den verknüpften Bestellungen geladen und an die DataContext-Eigenschaft des StackPanel gebunden, der das Stammlayoutsteuerelement für das WPF-Fenster ist. Weitere Informationen finden Sie unter Gewusst wie: Binden von Daten an Windows Presentation Foundation-Elemente (WCF Data Services).
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
Partial Public Class CustomerOrdersWpf3
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 _
Where cust.Country = customerCountry _
Select cust
' Create a new collection for binding based on the LINQ query.
trackedCustomers = New DataServiceCollection(Of Customer)(customerQuery)
' Load all pages of the response at once.
While trackedCustomers.Continuation IsNot Nothing
trackedCustomers.Load( _
context.Execute(Of Customer)(trackedCustomers.Continuation.NextLinkUri))
End While
' 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
Private Sub customerIDComboBox_SelectionChanged(ByVal sender As Object, ByVal e As SelectionChangedEventArgs)
Dim selectedCustomer As Customer = _
CType(Me.customerIDComboBox.SelectedItem, Customer)
Try
If selectedCustomer.Orders.Count = 0 Then
' Load the first page of related orders for the selected customer.
context.LoadProperty(selectedCustomer, "Orders")
End If
' Load all remaining pages.
While selectedCustomer.Orders.Continuation IsNot Nothing
selectedCustomer.Orders.Load( _
context.Execute(Of Order)(selectedCustomer.Orders.Continuation.NextLinkUri))
End While
Catch ex As Exception
MessageBox.Show(ex.ToString())
End Try
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;
namespace NorthwindClient
{
public partial class CustomerOrdersWpf3 : Window
{
private NorthwindEntities context;
private DataServiceCollection<Customer> trackedCustomers;
private const string customerCountry = "Germany";
private const string svcUri = "https://localhost:12345/Northwind.svc/";
public CustomerOrdersWpf3()
{
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
where cust.Country == customerCountry
select cust;
// Create a new collection for binding based on the LINQ query.
trackedCustomers = new DataServiceCollection<Customer>(customerQuery);
// Load all pages of the response at once.
while (trackedCustomers.Continuation != null)
{
trackedCustomers.Load(
context.Execute<Customer>(trackedCustomers.Continuation.NextLinkUri));
}
// Bind the root StackPanel element to the collection;
// related object binding paths are defined in the XAML.
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());
}
}
private void customerIDComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
Customer selectedCustomer =
this.customerIDComboBox.SelectedItem as Customer;
try
{
// Load the first page of related orders for the selected customer.
context.LoadProperty(selectedCustomer, "Orders");
// Load all remaining pages.
while (selectedCustomer.Orders.Continuation != null)
{
selectedCustomer.Orders.Load(
context.Execute<Order>(selectedCustomer.Orders.Continuation.NextLinkUri));
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
private void saveChangesButton_Click(object sender, RoutedEventArgs e)
{
try
{
// Save changes to the data service.
context.SaveChanges();
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
}
Siehe auch
Verweis
DataServiceCollection<T> Klasse
System.Data.Services.Client-Namespace