WPF3.5 使用BINDINGGROUP进行实体类和集合验证

前文介绍了自定义或系统自带的ValidationRule进行验证，这种方法对于单个元素的验证不错。很多时候，我们需要对表单(Form)进行验证，也就是对一个实体类进行验证，或者对一个集合的每项进行验证，则显得不尽人意（每次只能验证一次）。WPF3.5中提供了BindingGroup用来验证多个绑定元素，可以对表单(form)和实体类进行验证。另外BindingGroup提供了Transcational的支持，就是说可以让操作回滚(BeginEdit,CancelEdit,CommitEdit)。BindingGroup的验证是同时进行的。可以设置BindingGroupName把一个Binding加入已存在的BindingGroup(就是BindingGroupName指定的)。

MSDN上是这样说的：

BindingGroup 在多个绑定之间创建关系，从而可一起验证和更新这些绑定。例如，假定某应用程序提示用户输入地址。然后该应用程序使用用户提供的值填充 Address 类型的对象，该对象具有 Street、City、ZipCode 和 Country 属性。该应用程序有一个包含四个 TextBox 控件的面板，其中每个控件均数据绑定到对象的属性之一。可以使用 BindingGroup 中的 ValidationRule 验证 Address 对象。如果绑定加入相同的 BindingGroup，则可以确保邮政编码对于地址所在国家/地区有效。

设置 FrameworkElement 或 FrameworkContentElement 上的 BindingGroup 属性。正如任何其他可继承属性一样，子元素从其父元素继承 BindingGroup。如果发生以下情况之一，则会将子代元素上的绑定添加到 BindingGroup：

绑定的源和具有 BindingGroup 的元素的 DataContext 是同一对象，并且未设置 BindingGroupName 属性。
绑定的 BindingGroupName 属性等于 BindingGroup 的 Name，并且它们没有显式设置为 null引用（在 Visual Basic 中为 Nothing）。

在地址示例中，假定将 Panel 的 DataContext 设置为 Address 类型的对象。每个 TextBox 的绑定均添加到面板的 BindingGroup 中。

将 ValidationRule 对象添加到 BindingGroup 中。在运行 ValidationRule 时，将 BindingGroup 作为 Validate 方法的第一个参数传递。可以使用该 BindingGroup 上的 TryGetValue 或 GetValue(Object, String) 方法获取对象的建议值，使用 Items 属性获取绑定的源。

BindingGroup 在同一时间更新绑定的源，而不是分别更新每个绑定。在调用任一方法（ValidateWithoutUpdate、UpdateSources 或 CommitEdit）验证数据时，将验证并可能会更新示例中的每个 TextBox 的绑定。当绑定是 BindingGroup 的一部分时，除非显式设置 UpdateSourceTrigger 属性，否则在对 BindingGroup 调用 UpdateSources 或 CommitEdit 之前，不会更新绑定的源。

BindGroup常用成员：

public class BindingGroup : DependencyObject

{

  public Collection<BindingExpressionBase> BindingExpressions { get; }

  public bool CanRestoreValues { get; }

  public IList Items { get; }

  public string Name { get; set; }

  public bool NotifyOnValidationError { get; set; }

  public Collection<ValidationRule> ValidationRules { get; } 

  public void BeginEdit();

  public void CancelEdit();

  public bool CommitEdit();

  public object GetValue(object item, string propertyName);

  public bool TryGetValue(object item, string propertyName, out object value);

  public bool UpdateSources();

  public bool ValidateWithoutUpdate();

}

Items：BindingGroup 中的绑定对象所使用的源，是个List。所有作为源的对象都会被包含在Items中。通常，Items 中只有一项，即作为使用 BindingGroup 的元素的 DataContext 的对象。

但是，BindingGroup 也可以包含多个源。例如，如果绑定对象共享同一 BindingGroupName 但使用不同的源对象，则用作源的每个对象均在 Items 中。
如果绑定路径可解析为源的嵌套属性，则 Items 中也可有多个对象。例如，假定 TextBox 控件的绑定是 BindingGroup 的一部分，并且其 DataContext 是 Customer 对象，该对象具有 Address 类型的属性。
如果 Binding 的 Path 为 Address.ZipCode 属性，则 Address 会添加到 Items 属性中。

NotifyOnValidationError：获取或设置在 ValidationRule 的状态更改时是否发生 Validation.Error 事件。

BeginEdit：开始编辑事务。

CommitEdit：运行所有的Rule，如果成功，则保存更改，更新源。

CancelEdit：取消更改。

以上三个，如果源对应的类继承自IEditableObject， 会调用IEditableObject中的相应方法。

UpdateSources：运行所有ValidationStep设置为RawProposedValue、ConvertedProposedValue 或 UpdatedValue的Rule。如果成功，更新源。此方法不会挂起事务并结束事务，也就是说调用完该方法后事务还是处于运行中。

ValidateWithoutUpdate：如同UpdateSources，但是不会更新源。

所以有三个方法可以用作验证：CommitEdit，UpdateSources，ValidateWithoutUpdate。

先看看验证实体类的示例：

<Window x:Class="ValidateItemSample.Window1"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:src="clr-namespace:ValidateItemSample"

    Title="Validating an Object" Width="400" Height="500" ResizeMode="NoResize">

  <StackPanel Name="stackPanel1"  Margin="10"

              Loaded="stackPanel1_Loaded"

              Validation.Error="ItemError"><!--验证的错误在ItemError中处理，要求NotifyOnValidationError="True"--> 

    <StackPanel.Resources>

      <Style TargetType="HeaderedContentControl">

        <Setter Property="Margin" Value="2"/>

        <Setter Property="Focusable" Value="False"/>

        <Setter Property="Template">

          <Setter.Value>

            <ControlTemplate TargetType="HeaderedContentControl">

              <DockPanel LastChildFill="False">

                <ContentPresenter ContentSource="Header" DockPanel.Dock="Left" Focusable="False" VerticalAlignment="Center"/>

                <ContentPresenter ContentSource="Content" Margin="5,0,0,0" DockPanel.Dock="Right" VerticalAlignment="Center"/>

              </DockPanel>

            </ControlTemplate>

          </Setter.Value>

        </Setter>

      </Style>

      <Style TargetType="Button">

        <Setter Property="Width" Value="100"/>

        <Setter Property="Margin" Value="10,15,15,15"/>

      </Style>

    </StackPanel.Resources>

    <!--BindingGroup-->

    <StackPanel.BindingGroup>

      <BindingGroup NotifyOnValidationError="True">

        <BindingGroup.ValidationRules>

          <src:ValidateDateAndPrice ValidationStep="ConvertedProposedValue" />

        </BindingGroup.ValidationRules>

      </BindingGroup>

    </StackPanel.BindingGroup>

    <TextBlock FontSize="12" TextWrapping="Wrap" Margin="5">

      This sample demonstrates how to validate an object by checking

      multiple properties in a ValidationRule.  When a ValidationRule

      is added to a BindingGroup, the rule can get the properties of

      the source item in the Validate method.

      <LineBreak/><LineBreak/>

      This sample checks that if an item costs more than 100 dollars,

      the item is available for at least 7 days.

    </TextBlock>

    <TextBlock FontSize="14" FontWeight="Bold"

               Text="Enter an item for sale"/>

    <HeaderedContentControl Header="Description">

      <TextBox Width="150" Text="{Binding Path=Description, Mode=TwoWay}"/>

    </HeaderedContentControl>

    <HeaderedContentControl Header="Price">

      <TextBox Name="priceField"  Width="150">

        <TextBox.Text>

          <Binding Path="Price" Mode="TwoWay" >

            <!--自定义的ValidationRule-->

            <Binding.ValidationRules>

              <src:PriceIsAPositiveNumber/>

            </Binding.ValidationRules>

          </Binding>

        </TextBox.Text>

      </TextBox>

    </HeaderedContentControl>

    <HeaderedContentControl Header="Date Offer Ends">

      <TextBox Name="dateField" Width="150" >

        <TextBox.Text>

          <Binding Path="OfferExpires" StringFormat="d" >

            <!--自定义的ValidationRule-->

            <Binding.ValidationRules>

              <src:FutureDateRule/>

            </Binding.ValidationRules>

          </Binding>

        </TextBox.Text>

      </TextBox>

    </HeaderedContentControl>

    <StackPanel Orientation="Horizontal">

      <Button IsDefault="True" Click="Submit_Click">_Submit</Button>

      <Button IsCancel="True" Click="Cancel_Click">_Cancel</Button>

    </StackPanel>

    <HeaderedContentControl Header="Description">

      <TextBlock Width="150" Text="{Binding Path=Description}"/>

    </HeaderedContentControl>

    <HeaderedContentControl Header="Price">

      <TextBlock Width="150" Text="{Binding Path=Price, StringFormat=c}"/>

    </HeaderedContentControl>

    <HeaderedContentControl Header="Date Offer Ends">

      <TextBlock Width="150" Text="{Binding Path=OfferExpires, StringFormat=d}"/>

    </HeaderedContentControl>

  </StackPanel>

</Window>

        void stackPanel1_Loaded(object sender, RoutedEventArgs e)

        {

            // Set the DataContext to a PurchaseItem object.

            // The BindingGroup and Binding objects use this as

            // the source.

            stackPanel1.DataContext = new PurchaseItem();

            // Begin an edit transaction that enables

            // the object to accept or roll back changes.

            stackPanel1.BindingGroup.BeginEdit();

        }

        private void Submit_Click(object sender, RoutedEventArgs e)

        {

            //验证并提交

            if (stackPanel1.BindingGroup.CommitEdit())

            {

                MessageBox.Show("Item submitted");

                //提交成功后继续接收edit信息

                stackPanel1.BindingGroup.BeginEdit();

            }

        }

        private void Cancel_Click(object sender, RoutedEventArgs e)

        {

            // Cancel the pending changes and begin a new edit transaction.

            stackPanel1.BindingGroup.CancelEdit();

            stackPanel1.BindingGroup.BeginEdit();

        }

        // This event occurs when a ValidationRule in the BindingGroup

        // or in a Binding fails.

        private void ItemError(object sender, ValidationErrorEventArgs e)

        {

            if (e.Action == ValidationErrorEventAction.Added)//描述是添加还是清除了 ValidationError 对象

            {

                MessageBox.Show(e.Error.ErrorContent.ToString());

            }

        }

ValidationRule文件：

    public class ValidateDateAndPrice : ValidationRule

    {

        // Ensure that an item over $100 is available for at least 7 days.

        public override ValidationResult Validate(object value, CultureInfo cultureInfo)

        {

            BindingGroup bg = value as BindingGroup;

            // Get the source object.

            PurchaseItem item = bg.Items[0] as PurchaseItem;

            object doubleValue;

            object dateTimeValue;

            // Get the proposed values for Price and OfferExpires.

            bool priceResult = bg.TryGetValue(item, "Price", out doubleValue);

            bool dateResult = bg.TryGetValue(item, "OfferExpires", out dateTimeValue);

            if (!priceResult || !dateResult)

            {

                return new ValidationResult(false, "Properties not found");

            }

            double price = (double)doubleValue;

            DateTime offerExpires = (DateTime)dateTimeValue;

            // Check that an item over $100 is available for at least 7 days.

            if (price > 100)

            {

                if (offerExpires < DateTime.Today + new TimeSpan(7, 0, 0, 0))

                {

                    return new ValidationResult(false, "Items over $100 must be available for at least 7 days.");

                }

            }

            return ValidationResult.ValidResult;

        }

    }

    //Ensure that the price is positive.

    public class PriceIsAPositiveNumber : ValidationRule

    {

        public override ValidationResult Validate(object value, CultureInfo cultureInfo)

        {

            try

            {

                double price = Convert.ToDouble(value);

                if (price < 0)

                {

                    return new ValidationResult(false, "Price must be positive.");

                }

                else

                {

                    return ValidationResult.ValidResult;

                }

            }

            catch (Exception)

            {

                // Exception thrown by Conversion - value is not a number.

                return new ValidationResult(false, "Price must be a number.");

            }

        }

    }

    // Ensure that the date is in the future.

    class FutureDateRule : ValidationRule

    {

        public override ValidationResult Validate(object value, CultureInfo cultureInfo)

        {

            DateTime date;

            try

            {

                date = DateTime.Parse(value.ToString());

            }

            catch (FormatException)

            {

                return new ValidationResult(false, "Value is not a valid date.");

            }

            if (DateTime.Now.Date > date)

            {

                return new ValidationResult(false, "Please enter a date in the future.");

            }

            else

            {

                return ValidationResult.ValidResult;

            }

        }

    }

    // PurchaseItem implements INotifyPropertyChanged and IEditableObject

    // to support edit transactions, which enable users to cancel pending changes.

    public class PurchaseItem : INotifyPropertyChanged, IEditableObject

    {

        struct ItemData

        {

            internal string Description;

            internal double Price;

            internal DateTime OfferExpires;

            static internal ItemData NewItem()

            {

                ItemData data = new ItemData();

                data.Description = "New item";

                data.Price = 0;

                data.OfferExpires = DateTime.Now + new TimeSpan(7, 0, 0, 0);

                return data;

            }

        }

        ItemData copyData = ItemData.NewItem();

        ItemData currentData = ItemData.NewItem();

        public PurchaseItem()

        {

        }

        public PurchaseItem(string desc, double price, DateTime endDate)

        {

            Description = desc;

            Price = price;

            OfferExpires = endDate;

        }

        public override string ToString()

        {

            return String.Format("{0}, {1:c}, {2:D}", Description, Price, OfferExpires);

        }

        public string Description

        {

            get { return currentData.Description; }

            set

            {

                if (currentData.Description != value)

                {

                    currentData.Description = value;

                    NotifyPropertyChanged("Description");

                }

            }

        }

        public double Price

        {

            get { return currentData.Price; }

            set

            {

                if (currentData.Price != value)

                {

                    currentData.Price = value;

                    NotifyPropertyChanged("Price");

                }

            }

        }

        public DateTime OfferExpires

        {

            get { return currentData.OfferExpires; }

            set

            {

                if (value != currentData.OfferExpires)

                {

                    currentData.OfferExpires = value;

                    NotifyPropertyChanged("OfferExpires");

                }

            }

        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged(String info)

        {

            if (PropertyChanged != null)

            {

                PropertyChanged(this, new PropertyChangedEventArgs(info));

            }

        }

        #endregion

        #region IEditableObject Members

        public void BeginEdit()

        {

            copyData = currentData;

        }

        public void CancelEdit()

        {

            currentData = copyData;

            NotifyPropertyChanged("");

        }

        public void EndEdit()

        {

            copyData = ItemData.NewItem();

        }

        #endregion

    }

此例中PurchaseItem继承了IEditableObject，那么BindingGroup使用的BeginEdit,CancelEdit, EndEdit会使用IEditableObject中的相应方法。

对集合的验证：

下例点击Add Customer时，验证通过后会在集合中增加一个Customer对象，要求Customer所在区域与客服代表所在区域一致。

<Window x:Class="ValidateItemInItemsControlSample.Window1"

    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

    xmlns:sys="clr-namespace:System;assembly=mscorlib"

    xmlns:src="clr-namespace:ValidateItemInItemsControlSample"

    xmlns:diag="clr-namespace:System.Diagnostics;assembly=WindowsBase"

    Title="Window1">

  <StackPanel>

    <StackPanel.Resources>

      <!--枚举值做数据源，使用ObjectDataProvider，这里有介绍-->

      <!--方法原型是Enum.GetValues(Type)，返回值是一数组-->

      <ObjectDataProvider MethodName="GetValues"

                          ObjectType="{x:Type sys:Enum}"

                          x:Key="RegionValues">

        <ObjectDataProvider.MethodParameters>

          <x:Type TypeName="src:Region" />

        </ObjectDataProvider.MethodParameters>

      </ObjectDataProvider>

      <!—Representantives是ServiceRep(客服代表)实例的集合-->

      <src:Representantives x:Key="SaleReps"/>

      <!—集合中各项的模版-->

      <DataTemplate x:Key="ItemTemplate" >

        <StackPanel Orientation="Horizontal" >

          <TextBlock Text="Customer Name" Margin="5"/>

          <TextBox Width="100" Margin="5" Text="{Binding Name}"/>

          <TextBlock Text="Region" Margin="5"/>

          <ComboBox ItemsSource="{Binding Source={StaticResource RegionValues}}"

                    SelectedItem="{Binding Location}"  Width="100" Margin="5"/>

          <TextBlock Text="Service Representative" Margin="5"/>

          <ComboBox ItemsSource="{Binding Source={StaticResource SaleReps}}"

                    SelectedItem="{Binding ServiceRepresentative}"  Width="200" Margin="5"/>

          <Button Content="Save Customer" Click="saveCustomer_Click"/>

        </StackPanel>

      </DataTemplate>

    </StackPanel.Resources>

    <TextBlock FontSize="14" TextWrapping="Wrap" Margin="5">

      This sample demonstrates how to validate an object in an ItemsControl.

      The ValidationRule assigned to ItemsControl.ItemBindingGroup checks

      multiple properties in the item.

      This sample checks that a customer is assigned to a sales representative that serves their area.

    </TextBlock>

    <!—设置Itemtemplate和ItemSource--> 

//注意ItemsControl的使用，在界面上的显示效果

    <ItemsControl Margin="5"  Name="customerList"  ItemTemplate="{StaticResource ItemTemplate}"

                  ItemsSource="{Binding}">

      <ItemsControl.ItemBindingGroup>

        <BindingGroup>

          <BindingGroup.ValidationRules>

            <src:AreasMatch/>

          </BindingGroup.ValidationRules>

        </BindingGroup>

      </ItemsControl.ItemBindingGroup>

      <!—获取或设置 Style，它应用于为每个项生成的容器元素。这是一个依赖项属性-->

      <ItemsControl.ItemContainerStyle>

        <!—ItemsControl里的每项实际是以ContentPresenter作为UI显示的载体-->

        <Style TargetType="{x:Type ContentPresenter}">

          <Setter Property="Validation.ValidationAdornerSite"

                                                Value="{Binding ElementName=validationErrorReport}"/>

        </Style>

      </ItemsControl.ItemContainerStyle>

    </ItemsControl>

    <Label Name="validationErrorReport"

             Content="{Binding RelativeSource={RelativeSource Self},

           Path=(Validation.ValidationAdornerSiteFor).(Validation.Errors)[0].ErrorContent}"

           Margin="5" Foreground="Red" HorizontalAlignment="Center"/>

    <Button Content="Add Customer" Click="AddCustomer_Click" HorizontalAlignment="Center"/>

  </StackPanel>

</Window>

这里用了一个Label(validationErrorReport)来显示验证错误信息，验证的错误是以Validation.Errors这个Attached Property作为载体。

通过Validation.ValidationAdornerSite和Validation.ValidationAdornerSiteFor可以设置错误消息源(ItemsControl中的各项)和接收错误的载体(Label)。
但是这种做法是有点问题的，我在另一篇中会讲这个例子的运行效果。其有问题的原因是因为Validation类是静态类，里面的所有成员及方法都是静态的，只能对一个有效。

Backend code：

    public partial class Window1 : Window

    {

        Customers customerData;

        BindingGroup bindingGroupInError = null;

        public Window1()

        {

            InitializeComponent();

            customerData = new Customers();

            // 设置ItemsControl的源

            customerList.DataContext = customerData;

        }

        void AddCustomer_Click(object sender, RoutedEventArgs e)

        {

            if (bindingGroupInError == null)

            {

                customerData.Add(new Customer());

            }

            else

            {

                MessageBox.Show("Please correct the data in error before adding a new customer.");

            }

        }

        void saveCustomer_Click(object sender, RoutedEventArgs e)

        {

            Button btn = sender as Button;

            // ItemsControl.ContainerFromElement MSND上是这么说的：返回属于拥有给定元素的当前 ItemsControl 的容器。读起来和念易筋经一样
            FrameworkElement container = (FrameworkElement) customerList.ContainerFromElement(btn);

            // If the user is trying to change an items, when another item has an error,

            // display a message and cancel the currently edited item.

            if (bindingGroupInError != null && bindingGroupInError != container.BindingGroup)

            {

                MessageBox.Show("Please correct the data in error before changing another customer");

                container.BindingGroup.CancelEdit();

                return;

            }

            if (container.BindingGroup.ValidateWithoutUpdate())

            {

                container.BindingGroup.UpdateSources();

                bindingGroupInError = null;

                MessageBox.Show("Item Saved");

            }

            else

            {

                bindingGroupInError = container.BindingGroup;

            }

        }

ValicationRule文件：

    public class Customers : ObservableCollection<Customer>

    {

        public Customers()

        {

            Add(new Customer());

        }

    }

    public enum Region

    {

        Africa,

        Antartica,

        Australia,

        Asia,

        Europe,

        NorthAmerica,

        SouthAmerica

    }

    public class Customer

    {

        public string Name { get; set; }

        public ServiceRep ServiceRepresentative { get; set; }

        public Region Location { get; set; }

    }

    public class ServiceRep

    {

        public string Name { get; set; }

        public Region Area { get; set; }

        public ServiceRep()

        {

        }

        public ServiceRep(string name, Region area)

        {

            Name = name;

            Area = area;

        }

        public override string ToString()

        {

            return Name + " - " + Area.ToString();

        }

    }

    public class Representantives : ObservableCollection<ServiceRep>

    {

        public Representantives()

        {

            Add(new ServiceRep("Haluk Kocak", Region.Africa));

            Add(new ServiceRep("Reed Koch", Region.Antartica));

            Add(new ServiceRep("Christine Koch", Region.Asia));

            Add(new ServiceRep("Alisa Lawyer", Region.Australia));

            Add(new ServiceRep("Petr Lazecky", Region.Europe));

            Add(new ServiceRep("Karina Leal", Region.NorthAmerica));

            Add(new ServiceRep("Kelley LeBeau", Region.SouthAmerica));

            Add(new ServiceRep("Yoichiro Okada", Region.Africa));

            Add(new ServiceRep("T¨¹lin Oktay", Region.Antartica));

            Add(new ServiceRep("Preeda Ola", Region.Asia));

            Add(new ServiceRep("Carole Poland", Region.Australia));

            Add(new ServiceRep("Idan Plonsky", Region.Europe));

            Add(new ServiceRep("Josh Pollock", Region.NorthAmerica));

            Add(new ServiceRep("Daphna Porath", Region.SouthAmerica));

        }

    }

    // Check whether the customer and service representative are in the

    // same area.

    public class AreasMatch : ValidationRule

    {

        public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)

        {

            BindingGroup bg = value as BindingGroup;

            Customer cust = bg.Items[0] as Customer;

            if (cust == null)

            {

                return new ValidationResult(false, "Customer is not the source object");

            }

            Region region = (Region)bg.GetValue(cust, "Location");

            ServiceRep rep = bg.GetValue(cust, "ServiceRepresentative") as ServiceRep;

            string customerName = bg.GetValue(cust, "Name") as string;

            // 相等说明验证通过

            if (region == rep.Area)

            {

                return ValidationResult.ValidResult;

            }

            else

            {

                StringBuilder sb = new StringBuilder();

                sb.AppendFormat("{0} must be assigned a sales representative that serves the {1} region. \n ", customerName, region);

                return new ValidationResult(false, sb.ToString());

            }

        }

    }

http://www.cnblogs.com/iwteih/archive/2012/04/10/2441576.html

巴特西

WPF3.5 使用BINDINGGROUP进行实体类和集合验证

先看看验证实体类的示例：

对集合的验证：

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