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Specify Validation Rules for a Binding

<Window      x:Class="WpfApplication1.Window1"     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"     xmlns:WpfApplication1="clr-namespace:WpfApplication1"     Title="WPF" Height="100" Width="280">     <Window.Resources>         <Style              x:Key="textBoxInErrorStyle"              TargetType="{x:Type 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>             <Setter Property="Validation.ErrorTemplate">                 <Setter.Value>                     <ControlTemplate>                         <DockPanel DockPanel.Dock="Right">                             <AdornedElementPlaceholder/>                             <Image Source="Error.png" Width="16" Height="16"                                ToolTip="{Binding Path=AdornedElement.ToolTip, RelativeSource={RelativeSource                                              Mode=FindAncestor,                                             AncestorType={x:Type Adorner}}}"/>                         </DockPanel>                     </ControlTemplate>                 </Setter.Value>             </Setter>         </Style>     </Window.Resources>     <StackPanel>         <Slider Name="slider" Margin="4" Interval="1" TickFrequency="1" IsSnapToTickEnabled="True" Minimum="0" Maximum="100"/>         <StackPanel Orientation="Horizontal" >             <TextBox Style="{StaticResource textBoxInErrorStyle}" HorizontalAlignment="Center" >               <TextBox.Text>                     <Binding ElementName="slider" Path="Value" Mode="TwoWay"                         UpdateSourceTrigger="PropertyChanged" >                        <Binding.ValidationRules>                             <WpfApplication1:PercentageRule/>                         </Binding.ValidationRules>                     </Binding>                 </TextBox.Text>             </TextBox>          </StackPanel>     </StackPanel> </Window> //File:Window.xaml.vb Imports System.Globalization Imports System.Windows.Controls Namespace WpfApplication1   Public Class PercentageRule     Inherits ValidationRule     Public Overrides Function Validate(value As Object, cultureInfo As CultureInfo) As ValidationResult       Dim stringValue As String = TryCast(value, String)       If Not String.IsNullOrEmpty(stringValue) Then         Dim doubleValue As Double         If Double.TryParse(stringValue, doubleValue) Then           If doubleValue >= 0 AndAlso doubleValue <= 100 Then             Return New ValidationResult(True, Nothing)           End If         End If       End If       Return New ValidationResult(False, "Must be a number between 0 and 100")     End Function   End Class End Namespace