BindingExpressionBase.ValidateWithoutUpdate 方法

参考

定义

命名空间:: System.Windows.Data

程序集:: PresentationFramework.dll

重要

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对关联的 ValidationRule 运行 Binding 属性设置为 ValidationStep 或 RawProposedValue 的任何 ConvertedProposedValue 对象。此方法不更新源。

public:
 bool ValidateWithoutUpdate();

public bool ValidateWithoutUpdate ();

member this.ValidateWithoutUpdate : unit -> bool

Public Function ValidateWithoutUpdate () As Boolean

Boolean

如果验证规则成功，则为 true；否则为 false。

示例

以下示例演示了“备注”部分中讨论的方案。该示例允许用户输入库项的数据并提交数据。命名callNum的TextBox绑定具有ValidationRule与之关联的绑定。 TextBox当失去焦点时，示例调用 ValidateWithoutUpdate。当用户单击“提交”按钮时，示例将调用 UpdateSource 提交更改。以下 XAML 为应用程序创建用户界面。

<StackPanel>
    <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>

</StackPanel.Resources>
    <HeaderedContentControl Header="Title">
        <TextBox Width="150" Text="{Binding Path=Title, Mode=TwoWay}"/>
    </HeaderedContentControl>
    <HeaderedContentControl Header="Due Date">
        <TextBox Width="150" Text="{Binding Path=DueDate, StringFormat=d, Mode=TwoWay}">

        </TextBox>
    </HeaderedContentControl>
    
    <HeaderedContentControl Header="Call Number">
        <TextBox Name="CallNum" Width="150"
                 LostFocus="CallNum_LostFocus"
                 Validation.Error="CallNum_Error">
            <TextBox.Text>
                <Binding xmlns:src="clr-namespace:BindingExpressionBaseValidateWithoutUpdating"
                    Path="CallNumber" Mode="TwoWay"
                    NotifyOnValidationError="True"
                    UpdateSourceTrigger="Explicit">
                    <Binding.ValidationRules>
                        <src:CallNumberRule ValidationStep="ConvertedProposedValue"/>
                    </Binding.ValidationRules>
                </Binding>
            </TextBox.Text>
        </TextBox>
    </HeaderedContentControl>

    <Button Click="Button_Click">Submit</Button>
    
    <HeaderedContentControl Header="Title">
        <TextBlock Text="{Binding Path=Title, Mode=TwoWay}"/>
    </HeaderedContentControl>
    
    <HeaderedContentControl Header="Due Date">
        <TextBlock Text="{Binding Path=DueDate, StringFormat=d, Mode=TwoWay}"/>
    </HeaderedContentControl>
    
    <HeaderedContentControl Header="Call Number">
        <TextBlock Text="{Binding CallNumber}"/>
    </HeaderedContentControl>

</StackPanel>

以下示例显示了用户界面的逻辑。

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;

namespace BindingExpressionBaseValidateWithoutUpdating
{

    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            // Create an object and set it to the window's DataContext.
            LibraryItem item = new LibraryItem("Enter the title",
                    "Enter the call number",  DateTime.Now + new TimeSpan(14, 0, 0, 0));

            this.DataContext = item;
        }

        // Check whether the call number is valid when the
        // TextBox loses foces.
        private void CallNum_LostFocus(object sender, RoutedEventArgs e)
        {
            BindingExpression be = CallNum.GetBindingExpression(TextBox.TextProperty);

            be.ValidateWithoutUpdate();
        }

        // Show the validation error when one occurs.
        private void CallNum_Error(object sender, ValidationErrorEventArgs e)
        {
            if (e.Action == ValidationErrorEventAction.Added)
            {
                MessageBox.Show(e.Error.ErrorContent.ToString());
            }
        }

        // Update the source data object when the user clicks
        // the submit button.
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            BindingExpression be = CallNum.GetBindingExpression(TextBox.TextProperty);

            be.UpdateSource();
        }
    }
}

Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Data


Partial Public Class Window1
    Inherits Window
    Public Sub New()
        InitializeComponent()

        ' Create an object and set it to the window's DataContext.
        Dim item As New LibraryItem("Enter the title", "Enter the call number", DateTime.Now + New TimeSpan(14, 0, 0, 0))

        Me.DataContext = item
    End Sub

    ' Check whether the call number is valid when the
    ' TextBox loses foces.
    Private Sub CallNum_LostFocus(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim be As BindingExpression = CallNum.GetBindingExpression(TextBox.TextProperty)

        be.ValidateWithoutUpdate()
    End Sub


    ' Show the validation error when one occurs.
    Private Sub CallNum_Error(ByVal sender As Object, ByVal e As ValidationErrorEventArgs)
        If e.Action = ValidationErrorEventAction.Added Then
            MessageBox.Show(e.[Error].ErrorContent.ToString())

        End If
    End Sub

    ' Update the source data object when the user clicks
    ' the submit button.
    Private Sub Button_Click(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Dim be As BindingExpression = CallNum.GetBindingExpression(TextBox.TextProperty)

        be.UpdateSource()
    End Sub
End Class

以下示例显示了数据对象和 ValidationRule 应用程序。

using System;
using System.ComponentModel;
using System.Windows.Controls;
using System.Globalization;

namespace BindingExpressionBaseValidateWithoutUpdating
{
    // LibraryItem implements INotifyPropertyChanged so that the 
    // application is notified when a property changes.  It 
    // implements IEditableObject so that pending changes can be discarded.
    // In this example, the application does not discard changes.
    public class LibraryItem : INotifyPropertyChanged, IEditableObject
    {
        struct ItemData
        {
            internal string Title;
            internal string CallNumber;
            internal DateTime DueDate;
        }

        ItemData copyData;
        ItemData currentData;

        public LibraryItem(string title, string callNum, DateTime dueDate)
        {
            Title = title;
            CallNumber = callNum;
            DueDate = dueDate;
        }

        public string Title
        {
            get { return currentData.Title; }
            set
            {
                if (currentData.Title != value)
                {
                    currentData.Title = value;
                    NotifyPropertyChanged("Title");
                }
            }
        }

        public string CallNumber
        {
            get { return currentData.CallNumber; }
            set
            {
                if (currentData.CallNumber != value)
                {
                    currentData.CallNumber = value;
                    NotifyPropertyChanged("CallNumber");
                }
            }
        }

        public DateTime DueDate
        {
            get { return currentData.DueDate; }
            set
            {
                if (value != currentData.DueDate)
                {
                    currentData.DueDate = value;
                    NotifyPropertyChanged("DueDate");
                }
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        protected void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }

        #endregion

        #region IEditableObject Members

        public virtual void BeginEdit()
        {
            copyData = currentData;
        }

        public virtual void CancelEdit()
        {
            currentData = copyData;
            NotifyPropertyChanged("");
        }

        public virtual void EndEdit()
        {
            copyData = new ItemData();
        }

        #endregion

    }

    public class CallNumberRule : ValidationRule
    {
        // A valid call number contains a period (.)
        // and 6 characters after the period.
        public override ValidationResult Validate(object value, 
                                         CultureInfo cultureInfo)
        {
            string callNum = (string)value;

            int dotIndex = callNum.IndexOf(".");
            if (dotIndex == -1 || dotIndex == 0)
            {
                return new ValidationResult(false, 
                    "There must be characters followed by a period (.) in the call number.");
            }

            string substr = callNum.Substring(dotIndex + 1);

            if (substr.Length != 6)
            {
                return new ValidationResult(false, 
                    "The call number must have 6 characters after the period (.).");
            }

            return ValidationResult.ValidResult;
        }
    }
}

Imports System.ComponentModel
Imports System.Windows.Controls
Imports System.Globalization

' LibraryItem implements INotifyPropertyChanged so that the 
' application is notified when a property changes. It 
' implements IEditableObject so that pending changes can be discarded.
' In this example, the application does not discard changes.
Public Class LibraryItem
    Implements INotifyPropertyChanged
    Implements IEditableObject
    Private Structure ItemData
        Friend Title As String
        Friend CallNumber As String
        Friend DueDate As DateTime
    End Structure

    Private copyData As ItemData
    Private currentData As ItemData

    Public Sub New(ByVal title As String, ByVal callNum As String, ByVal dueDate As DateTime)
        Me.Title = title
        Me.CallNumber = callNum
        Me.DueDate = DueDate
    End Sub

    Public Property Title() As String
        Get
            Return currentData.Title
        End Get
        Set(ByVal value As String)
            If currentData.Title <> value Then
                currentData.Title = value
                NotifyPropertyChanged("Title")
            End If
        End Set
    End Property

    Public Property CallNumber() As String
        Get
            Return currentData.CallNumber
        End Get
        Set(ByVal value As String)
            If currentData.CallNumber <> value Then
                currentData.CallNumber = value
                NotifyPropertyChanged("CallNumber")
            End If
        End Set
    End Property

    Public Property DueDate() As DateTime
        Get
            Return currentData.DueDate
        End Get
        Set(ByVal value As DateTime)
            If value <> currentData.DueDate Then
                currentData.DueDate = value
                NotifyPropertyChanged("DueDate")
            End If
        End Set
    End Property

#Region "INotifyPropertyChanged Members"

    Public Event PropertyChanged As PropertyChangedEventHandler _
        Implements INotifyPropertyChanged.PropertyChanged

    Protected Sub NotifyPropertyChanged(ByVal info As [String])
        RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(info))
    End Sub

#End Region

#Region "IEditableObject Members"

    Public Overridable Sub BeginEdit() _
        Implements IEditableObject.BeginEdit

        copyData = currentData
    End Sub

    Public Overridable Sub CancelEdit() _
        Implements IEditableObject.CancelEdit

        currentData = copyData

        NotifyPropertyChanged("")
    End Sub

    Public Overridable Sub EndEdit() _
        Implements IEditableObject.EndEdit

        copyData = New ItemData()
    End Sub

#End Region

End Class

Public Class CallNumberRule
    Inherits ValidationRule

    ' A valid call number contains a period (.)
    ' and 6 characters after the period.
    Public Overloads Overrides Function Validate(ByVal value As Object,
                               ByVal cultureInfo As CultureInfo) As ValidationResult

        Dim callNum As String = DirectCast(value, String)

        Dim dotIndex As Integer = callNum.IndexOf(".")

        If dotIndex = -1 OrElse dotIndex = 0 Then
            Return New ValidationResult(False,
                "There must be characters followed by a period (.) in the call number.")
        End If

        Dim substr As String = callNum.Substring(dotIndex + 1)

        If substr.Length <> 6 Then
            Return New ValidationResult(False,
                "The call number must have 6 characters after the period (.).")
        End If

        Return ValidationResult.ValidResult
    End Function
End Class

注解

使用此方法 ValidateWithoutUpdate 可以在绑定上运行验证规则，而无需更新绑定的源。如果要验证用户输入并在应用程序中的不同时间更新源，这非常有用。

例如，假设你有一个表单来更新包含提交按钮的数据源。如果用户尝试提交表单之前输入了无效值，则希望向用户提供反馈。可以通过将绑定UpdateSourceTrigger的属性Explicit设置为失去焦点时TextBox调用来ValidateWithoutUpdate检查字段的有效性。

适用于

通过

BindingExpressionBase.ValidateWithoutUpdate 方法

定义

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示例

注解

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