BindingExpressionBase.ValidateWithoutUpdate Método
Definição
Importante
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Executa quaisquer objetos ValidationRule no Binding associado que têm a propriedade ValidationStep definida como RawProposedValue ou ConvertedProposedValue. Este método não atualiza a origem.
public:
bool ValidateWithoutUpdate();
public bool ValidateWithoutUpdate ();
member this.ValidateWithoutUpdate : unit -> bool
Public Function ValidateWithoutUpdate () As Boolean
Retornos
true
se as regras de validação tiverem sido bem-sucedidas; caso contrário, false
.
Exemplos
O exemplo a seguir demonstra o cenário discutido na seção Comentários. O exemplo permite que um usuário insira dados para um item de biblioteca e envie os dados. A associação para o TextBox nomeado callNum
tem um ValidationRule associado a ele. Quando o perde o TextBox foco, o exemplo chama ValidateWithoutUpdate. Quando o usuário clica no botão enviar, o exemplo chama UpdateSource para confirmar as alterações. O XAML a seguir cria a interface do usuário para o aplicativo.
<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>
O exemplo a seguir mostra a lógica da interface do usuário.
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
O exemplo a seguir mostra o objeto de dados e ValidationRule para o aplicativo.
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
Comentários
O ValidateWithoutUpdate método permite executar regras de validação em uma associação sem atualizar a origem da associação. Isso é útil quando você deseja validar a entrada do usuário e atualizar a origem em momentos diferentes em um aplicativo.
Por exemplo, suponha que você tenha um formulário para atualizar uma fonte de dados que contém um botão enviar. Você deseja fornecer comentários ao usuário se um valor inválido for inserido antes que o usuário tente enviar o formulário. Você pode verificar a validade de um campo definindo a propriedade da UpdateSourceTrigger associação Explicit como e chamando ValidateWithoutUpdate quando o perde o TextBox foco.