EntityCollectionChangedParams Klasse

Definition

Namespace:

System.Data.Services.Client

Assembly:

System.Data.Services.Client.dll

Kapselt die Argumente eines CollectionChanged-Delegaten.

public ref class EntityCollectionChangedParams sealed

public sealed class EntityCollectionChangedParams

type EntityCollectionChangedParams = class

Public NotInheritable Class EntityCollectionChangedParams

Vererbung

Object

EntityCollectionChangedParams

Beispiele

Die folgende Code-Behind-Seite für die XAML-Datei erstellt eine DataServiceCollection<T>-Instanz mit benutzerdefinierten Methoden, die aufgerufen werden, wenn Änderungen an Daten auftreten, die an die Bindungssammlung gebunden sind. Wenn das CollectionChanged-Ereignis eintritt, verhindert die angegebene Methode, dass ein aus der Bindungsauflistung entferntes Element aus dem Datendienst gelöscht wird. Wenn das PropertyChanged-Ereignis eintritt, wird der ShipDate-Wert überprüft, um sicherzustellen, dass keine Änderungen an bereits ausgelieferten Bestellungen vorgenommen werden.

using System;
using System.Collections.Specialized;
using System.Data.Services.Client;
using System.Linq;
using System.Windows;
using NorthwindClient.Northwind;

namespace NorthwindClient
{
    public partial class CustomerOrdersCustom : Window
    {
        private NorthwindEntities context;
        private DataServiceCollection<Customer> trackedCustomers;
        private const string customerCountry = "Germany";
        private const string svcUri = "http://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.
                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());
            }
        }
    }
}

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 = "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.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

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.NorthwindModel
Imports System.Collections.Specialized

Partial Public Class CustomerOrdersCustom
    Inherits Window
    Private context As NorthwindEntities
    Private trackedCustomers As DataServiceCollection(Of Customers)
    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.Expand("Orders") _
                                    Where cust.Country = customerCountry _
                                    Select cust

            ' Create a new collection for binding based on the LINQ query.
            trackedCustomers = New DataServiceCollection(Of Customers)(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
                Me.LayoutRoot.UpdateLayout()
        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(Orders) Then

                ' Get the context and object from the supplied parameter.
                Dim context = entityCollectionChangedinfo.Context
                Dim deletedOrder As Orders = _
                CType(entityCollectionChangedinfo.TargetEntity, Orders)

                ' Load the related OrderDetails.
                context.LoadProperty(deletedOrder, "Order_Details")

                ' Delete the order and its related items
                For Each item As Order_Details In deletedOrder.Order_Details
                    'context.DeleteLink(deletedOrder, "Order_Details", item)
                    context.DeleteObject(item)
                Next

                ' Delete the order and then return false since the object is already deleted.
                context.DeleteObject(deletedOrder)

                Return False
            Else
                Return True
            End If
        Else
            ' Use the default behavior.
            Return True
        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(Orders) AndAlso _
            (CType(entityChangedInfo.Entity, Orders).ShippedDate < DateTime.Today) Then
            Throw New ApplicationException(String.Format( _
                "The order {0} cannot be changed because it shipped on {1}.", _
                CType(entityChangedInfo.Entity, Orders).OrderID, _
                CType(entityChangedInfo.Entity, Orders).ShippedDate))
            Return True
        End If
    End Function
    Private Sub deleteButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
        ' Get the Orders binding collection.
        Dim trackedOrders As DataServiceCollection(Of Orders) = _
            (CType(customerIDComboBox.SelectedItem, Customers)).Orders

        ' Remove the currently selected order.
        trackedOrders.Remove(CType(ordersDataGrid.SelectedItem, Orders))
    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

Der folgende XAML-Code definiert das Fenster für das vorherige Beispiel.

<Window x:Class="CustomerOrdersCustom"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://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>

Eigenschaften

Action	Ein NotifyCollectionChangedAction-Wert, der angibt, wie die Auflistung geändert wurde.
Collection	Die DataServiceCollection<T>, die geändert wurde.
Context	Der DataServiceContext der DataServiceCollection<T>, die geändert wurde.
PropertyName	Die Navigationseigenschaft im Quellobjekt, die auf die geänderte Auflistung verweist.
SourceEntity	Das Quellobjekt, das in der Auflistung mit einer Navigationseigenschaft auf das Zielobjekt verweist.
SourceEntitySet	Die Entitätenmenge des Quellobjekts.
TargetEntity	Das Entitätsobjekt in der Auflistung, die geändert wurde.
TargetEntitySet	Der Entitätenmengenname des Objekts in der Auflistung.

Methoden

Equals(Object)	Bestimmt, ob das angegebene Objekt gleich dem aktuellen Objekt ist. (Geerbt von Object)
GetHashCode()	Fungiert als Standardhashfunktion. (Geerbt von Object)
GetType()	Ruft den Type der aktuellen Instanz ab. (Geerbt von Object)
MemberwiseClone()	Erstellt eine flache Kopie des aktuellen Object. (Geerbt von Object)
ToString()	Gibt eine Zeichenfolge zurück, die das aktuelle Objekt darstellt. (Geerbt von Object)

Weitere Informationen

• Binden von Daten an Steuerelemente (WCF Data Services)
• Gewusst wie: Anpassen des Datenbindungsverhaltens (WCF Data Services)