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Binding.ValidatesOnExceptions Property

Updated: June 2010

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

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

public bool ValidatesOnExceptions { get; set; }
<object ValidatesOnExceptions="bool" .../>

Property Value

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

Setting this property provides an alternative to using the ExceptionValidationRule element explicitly. The ExceptionValidationRule is a built-in validation rule that checks for exceptions that are thrown during the update of the source property. If an exception is thrown, the binding engine creates a ValidationError with the exception 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.

ValidatesOnExceptions is introduced in the .NET Framework version 3.5. For more information, see .NET Framework 3.5 Architecture.

The following examples use ValidatesOnExceptions to validate user input in a TextBox. The first example creates a data type that throws an exception when the Age property is set to an invalid property.

public class PersonThrowException
{
    private int age;

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

            if (value < 0 || value > 150)
            {
                throw new ArgumentException("Age must not be less than 0 or greater than 150.");
            }
            age = value;
        }
    }
}

The following example binds the Age property to the TextBox and sets ValidatesOnExceptions 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:PersonThrowException 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>
      <!--By setting ValidatesOnExceptions to True, it checks for exceptions
        that are thrown during the update of the source property.
        An alternative syntax is to add <ExceptionValidationRule/> within
        the <Binding.ValidationRules> section.-->
      <Binding Path="Age" Source="{StaticResource data}"
               ValidatesOnExceptions="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

Date

History

Reason

June 2010

Fixed example.

January 2010

Added correct example.

Content bug fix.

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