Binding.ValidatesOnExceptions Property

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

public bool ValidatesOnExceptions { get; set; }

member this.ValidatesOnExceptions : bool with get, set

Public Property ValidatesOnExceptions As Boolean

Property Value

true to include the ExceptionValidationRule; otherwise, false.

Examples

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;
 }
 }
}

Public Class PersonThrowException
 Private m_age As Integer

 Public Property Age() As Integer
 Get
 Return m_age
 End Get
 Set(ByVal value As Integer)

 If value < 0 OrElse value > 150 Then
 Throw New ArgumentException("Age must not be less than 0 or greater than 150.")
 End If
 m_age = value
 End Set
 End Property
End Class

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>

Remarks

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 Versions and Dependencies.

See also

• ValidatesOnDataErrors