Binding.ValidatesOnDataErrors Property (System.Windows.Data)

.NET Framework Class Library

Binding..::.ValidatesOnDataErrors Property

Updated: February 2009

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

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

Syntax

Visual Basic (Declaration)

Public Property ValidatesOnDataErrors As Boolean

Visual Basic (Usage)

Dim instance As Binding
Dim value As Boolean

value = instance.ValidatesOnDataErrors

instance.ValidatesOnDataErrors = value

public bool ValidatesOnDataErrors { get; set; }

Visual C++

public:
property bool ValidatesOnDataErrors {
    bool get ();
    void set (bool value);
}

JScript

public function get ValidatesOnDataErrors () : boolean
public function set ValidatesOnDataErrors (value : boolean)

XAML Attribute Usage

<object ValidatesOnDataErrors="bool" .../>

Property Value

Type: System..::.Boolean
true to include the DataErrorValidationRule; otherwise, false.

Remarks

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.

Examples

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.

Visual Basic

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

public class PersonImplementsIDataErrorInfo : IDataErrorInfo
{
    private int age;

    public int Age
    {
        get { return age; }
        set { age = value; }
    }

    public string Error
    {
        get
        {
            return null;
        }
    }

    public string this[string name]
    {
        get
        {
            string result = null;

            if (name == "Age")
            {
                if (this.age < 0 || this.age > 150)
                {
                    result = "Age must not be less than 0 or greater than 150.";
                }
            }
            return result;
        }
    }
}

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.

XAML

<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>

Platforms

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.

Version Information