EntityChangedParams 类

定义

public ref class EntityChangedParams sealed

public sealed class EntityChangedParams

type EntityChangedParams = class

Public NotInheritable Class EntityChangedParams

继承

Object

EntityChangedParams

示例

XAML 文件的以下代码隐藏页创建一个 DataServiceCollection<T> 自定义方法，这些方法在对绑定到绑定集合的数据进行更改时调用。 CollectionChanged事件发生时，提供的方法可防止从绑定集合中删除的项从数据服务中删除。 PropertyChanged事件发生时，ShipDate将验证该值，以确保不会对已发货的订单进行更改。

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.Specialized
Imports System.Data.Services.Client
Imports System.Windows
Imports northwindclientvb.Northwind

Partial Public Class CustomerOrdersCustom
    Inherits Window
    Private context As NorthwindEntities
    'Private trackedCustomers As DataServiceCollection(Of Customer)
    '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))

    '        '<snippetMasterDetailBinding>
    '        ' 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
    '        '</snippetMasterDetailBinding>
    '    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.Specialized
Imports System.Data.Services.Client
Imports System.Linq
Imports System.Windows
Imports northwindclientvb.Northwind
Imports northwindclientvb.NorthwindModel

Partial Public Class CustomerOrdersCustom
    Inherits Window
    Private _context As Northwind.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 Northwind.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
            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))
        End If
        Return True
    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

以下 XAML 代码定义上一示例的窗口。

<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>

另请参阅

• 将数据绑定到控件（WCF 数据服务）
• 如何：自定义数据绑定行为（WCF 数据服务）