DataServiceCollection<T>.Continuation Proprietà

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, set

Public Property Continuation As DataServiceQueryContinuation(Of T)

Valore della proprietà

Oggetto DataServiceQueryContinuation<T> che contiene l'URI per restituire il set successivo di risultati di paging.

Esempio

L'esempio seguente è tratto dalla pagina code-behind per una pagina XAML (Extensible Application Markup Language) che definisce la finestra SalesOrders in WPF. Quando viene caricata la finestra, viene creato un oggetto DataServiceCollection<T> in base al risultato di una query che restituisce i clienti, filtrati per paese/area geografica. Tutte le pagine di questo risultato di paging vengono caricate insieme agli ordini correlati e vengono associate alla proprietà DataContext dell'oggetto StackPanel che rappresenta il controllo di layout radice per la finestra WPF. Per altre informazioni, vedere Procedura: Associare dati a elementi Windows Presentation Foundation.

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

Commenti

La proprietà Continuation restituisce un collegamento utilizzato per accedere al set successivo di risultati di paging se quest'ultimo è abilitato nel servizio dati. Per altre informazioni, vedere Configurazione del servizio dati.

Quando si carica un risultato di paging in un oggetto DataServiceCollection<T>, è necessario caricare pagine in modo esplicito chiamando il metodo Load(IEnumerable<T>) sull'oggetto DataServiceCollection<T> passando il risultato dell'esecuzione dell'URI ottenuto dalla proprietà Continuation.

Si applica a

Vedi anche

• Caricamento di contenuto posticipato (WCF Data Services)
• Associazione di dati a controlli (WCF Data Services)