ValidatesOnDataErrors Property

Binding.ValidatesOnDataErrors Property

 

Gets or sets a value that indicates whether to include the DataErrorValidationRule.

Namespace:   System.Windows.Data
Assembly:  PresentationFramework (in PresentationFramework.dll)

Public Property ValidatesOnDataErrors As Boolean

Property Value

Type: System.Boolean

true to include the DataErrorValidationRule; otherwise, false.

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 Versions and Dependencies.

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 ""
        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 ToolTip reports the error message.

<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>

.NET Framework
Available since 3.0
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 7.1
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