EntityChangedParams 類別

定義

命名空間:

System.Data.Services.Client

組件:

System.Data.Services.Client.dll

封裝 PropertyChanged 委派的引數。

public ref class EntityChangedParams sealed

public sealed class EntityChangedParams

type EntityChangedParams = class

Public NotInheritable Class EntityChangedParams

繼承

Object

EntityChangedParams

範例

XAML 檔案的下列程式代碼後置頁面會使用自定義方法建立 ， DataServiceCollection<T> 這些方法會在系結至系結集合的數據發生變更時呼叫。 發生 CollectionChanged 事件時，所提供的方法會防止已從繫結集合移除的項目從資料服務中刪除。 發生 PropertyChanged 事件時，會驗證 ShipDate 值，確保已出貨的訂單不會遭到變更。

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

下列 XAML 程式代碼會定義上一個範例的視窗。

<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>

屬性

Context	與已變更之實體物件相關聯的內容。
Entity	已變更的實體物件。
PropertyName	實體物件上參考目標物件的屬性名稱。
PropertyValue	實體物件上已變更之屬性目前所參考的物件。
SourceEntitySet	來源物件的實體集。
TargetEntitySet	目標實體物件所屬的實體集。

方法

Equals(Object)	判斷指定的物件是否等於目前的物件。 (繼承來源 Object)
GetHashCode()	做為預設雜湊函式。 (繼承來源 Object)
GetType()	取得目前執行個體的 Type。 (繼承來源 Object)
MemberwiseClone()	建立目前 Object 的淺層複製。 (繼承來源 Object)
ToString()	傳回代表目前物件的字串。 (繼承來源 Object)

另請參閱

• 將資料繫結至控制項 (WCF 資料服務)
• 如何：自訂資料繫結行為 (WCF 資料服務)