Updated: February 2009
Namespace:
System.Windows.Data
Assembly:
PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
'Usage
Dim instance As Binding
Dim value As Boolean
value = instance.ValidatesOnDataErrors
instance.ValidatesOnDataErrors = value
'Declaration
Public Property ValidatesOnDataErrors As Boolean
<object ValidatesOnDataErrors="bool" .../>
Setting this property provides an alternative to using the DataErrorValidationRule element explicitly. The DataErrorValidationRule is a built-in validation rule that checks for errors that are raised by the IDataErrorInfo implementation of the source object. If an error is raised, the binding engine creates a ValidationError with the error and adds it to the Validation..::.Errors collection of the bound element. The lack of an error clears this validation feedback, unless another rule raises a validation issue.
ValidatesOnDataErrors is introduced in the .NET Framework version 3.5. For more information, see .NET Framework 3.5 Architecture.
The following examples uses IDataErrorInfo and ValidatesOnDataErrors to validate user input in a TextBox. The first example creates a data type that implements IDataErrorInfo to report validation errors.
Public Class PersonImplementsIDataErrorInfo
Implements System.ComponentModel.IDataErrorInfo
Private m_age As Integer
Public Property Age() As Integer
Get
Return m_age
End Get
Set(ByVal value As Integer)
m_age = value
End Set
End Property
Public ReadOnly Property [Error]() As String _
Implements System.ComponentModel.IDataErrorInfo.Error
Get
Return Nothing
End Get
End Property
Default Public ReadOnly Property Item(ByVal name As String) As String _
Implements System.ComponentModel.IDataErrorInfo.Item
Get
Dim result As String = Nothing
If name = "Age" Then
If Me.m_age < 0 OrElse Me.m_age > 150 Then
result = "Age must not be less than 0 or greater than 150."
End If
End If
Return result
End Get
End Property
End Class
The following example binds the Age property to the TextBox and sets ValidatesOnDataErrors to true on the Binding. When the user enters an invalid value, a red border appears in the TextBox and the [System.Windows.Controls.ToolTip] reports the error message.
<StackPanel>
<StackPanel Margin="20">
<StackPanel.Resources>
<src:PersonImplementsIDataErrorInfo x:Key="data"/>
<!--The tool tip for the TextBox to display the validation error message.-->
<Style x:Key="textBoxInError" TargetType="TextBox">
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={x:Static RelativeSource.Self},
Path=(Validation.Errors)[0].ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>
</StackPanel.Resources>
<TextBlock>Enter your age:</TextBlock>
<TextBox Style="{StaticResource textBoxInError}">
<TextBox.Text>
<!--ValidatesOnDataErrors to is set to True, so the Binding
checks for errors raised by the IDataErrorInfo object.
An alternative syntax is to add <DataErrorValidationRule/> within
the <Binding.ValidationRules> section.-->
<Binding Path="Age" Source="{StaticResource data}"
ValidatesOnDataErrors="True"
UpdateSourceTrigger="PropertyChanged">
</Binding>
</TextBox.Text>
</TextBox>
<TextBlock>Mouse-over to see the validation error message.</TextBlock>
</StackPanel>
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5 SP1, 3.0 SP1
Reference
Other Resources
Date | History | Reason |
|---|
February 2009
| Added example. |
Customer feedback.
|