EntityChangedParams Class

Encapsulates the arguments of a PropertyChanged delegate

Namespace:  System.Data.Services.Client
Assembly:  System.Data.Services.Client (in System.Data.Services.Client.dll)

public sealed class EntityChangedParams

This topic describes new functionality in ADO.NET Data Services that is available as an update to the .NET Framework version 3.5 Service Pack 1. You can download and install the update from the Microsoft Download Center.

The following code-behind page for the XAML file creates an DataServiceCollection<T> with custom methods that are called when changes occur to data that is bound to the binding collection. When the CollectionChanged event occurs, the supplied method prevents an item that has been removed from the binding collection from being deleted from the data service. When the PropertyChanged event occurs, the ShipDate value is validated to ensure that changes are not made to orders that have already shipped.

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.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 occured:\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
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 NorthwindModel;
using System.Collections.Specialized;

namespace NorthwindClient
{
    public partial class CustomerOrdersCustom : Window
    {
        private NorthwindEntities context;
        private DataServiceCollection<Customers> 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<Customers>(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 occured:\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(Orders))
                {
                    // Get the context and object from the supplied parameter.
                    DataServiceContext context = entityCollectionChangedinfo.Context;
                    Orders deletedOrder = entityCollectionChangedinfo.TargetEntity as Orders;

                    if (deletedOrder.Order_Details.Count == 0)
                    {
                        // Load the related OrderDetails.
                        context.LoadProperty(deletedOrder, "Order_Details");
                    }

                    // Delete the order and its related items; 
                    foreach (Order_Details item in deletedOrder.Order_Details)
                    {
                        //context.DeleteLink(deletedOrder, "Order_Details", item);
                        context.DeleteObject(item);
                    }

                    // Delete the order and then return false 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(Orders)) && 
                ((Orders)(entityChangedInfo.Entity)).ShippedDate < DateTime.Today)
            {
                throw new ApplicationException(string.Format(
                    "The order {0} cannot be changed because it shipped on {1}.",
                    ((Orders)(entityChangedInfo.Entity)).OrderID, 
                    ((Orders)(entityChangedInfo.Entity)).ShippedDate));
            }
            return false;
        }

        private void deleteButton_Click(object sender, RoutedEventArgs e)
        {
            if (customerIDComboBox.SelectedItem != null)
            {
                // Get the Orders binding collection.
                DataServiceCollection<Orders> trackedOrders =
                    ((Customers)(customerIDComboBox.SelectedItem)).Orders;

                // Remove the currently selected order.
                trackedOrders.Remove((Orders)(ordersDataGrid.SelectedItem));
            }
        }

        private void saveChangesButton_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                // Save changes to the data service.
                context.SaveChanges();
            }
            catch (DataServiceClientException ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }
    }
}

The following XAML code defines the window for the previous example.

    <Window x:Class="NorthwindClient.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>

System.Object
  System.Data.Services.Client.EntityChangedParams

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5 SP1
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