EntityChangedParams Class
Encapsulates the arguments of a PropertyChanged delegate
Assembly: System.Data.Services.Client (in System.Data.Services.Client.dll)
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(Of 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
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 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) 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_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 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(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 False End If End Function Private Sub deleteButton_Click(ByVal sender As Object, ByVal e As RoutedEventArgs) If customerIDComboBox.SelectedItem IsNot Nothing Then ' 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 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
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>
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.