DataServiceCollection<T>.Continuation Property
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Gets a continuation object that is used to return the next set of paged results.
public:
property System::Data::Services::Client::DataServiceQueryContinuation<T> ^ Continuation { System::Data::Services::Client::DataServiceQueryContinuation<T> ^ get(); void set(System::Data::Services::Client::DataServiceQueryContinuation<T> ^ value); };public System.Data.Services.Client.DataServiceQueryContinuation<T> Continuation { get; set; }member this.Continuation : System.Data.Services.Client.DataServiceQueryContinuation<'T> with get, setPublic Property Continuation As DataServiceQueryContinuation(Of T)Property Value
A DataServiceQueryContinuation<T> object that contains the URI to return the next set of paged results.
Examples
The following example is from the code-behind page for an Extensible Application Markup Language (XAML) page that defines the SalesOrders window in WPF. When the window is loaded, a DataServiceCollection<T> is created based on the result of a query that returns customers, filtered by country/region. All of the pages of this paged result are loaded, along with the related orders, and are bound to the DataContext property of the StackPanel that is the root layout control for the WPF window. For more information, see How to: Bind Data to Windows Presentation Foundation Elements.
using System;
using System.Data.Services.Client;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
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 = "http://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());
}
}
}
}
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 = "http://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
Remarks
The Continuation property returns a link that is used to access the next set of paged results when paging is enabled in the data service. For more information, see Configuring the Data Service.
When loading a paged result into a DataServiceCollection<T>, you must explicitly load pages by calling the Load(IEnumerable<T>) method on the DataServiceCollection<T> by passing the result of the execution of the URI that was obtained from the Continuation property.
