WPF: TextBox Error Notification Through Style
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By default, WPF doesn’t provide any visual indication when ValidationRules aren’t met for TextBoxes. When I was learning WPF, I read a post about providing error notification for TextBoxes through the user of a style. I can’t find the article/post, but it never worked properly for me so I’ve modified and fixed what I had. This only works if there are ValidationRules bound to the TextBox, and it only displays the first failed rule.
<Style TargetType="{x:Type TextBoxBase}" x:Key="{x:Type TextBox}"> <Setter Property="Margin" Value="2" /> <Setter Property="SnapsToDevicePixels" Value="True"/> <Setter Property="OverridesDefaultStyle" Value="false"/> <Setter Property="KeyboardNavigation.TabNavigation" Value="None"/> <Setter Property="FocusVisualStyle" Value="{x:Null}"/> <Setter Property="MinWidth" Value="80"/> <Setter Property="MinHeight" Value="20"/> <Setter Property="AllowDrop" Value="true"/> <Setter Property="Background" Value="{StaticResource WindowBackgroundBrush}" /> <Setter Property="BorderBrush" Value="{StaticResource SolidBorderBrush}" /> <Setter Property="Template"> ...
The rest is after the jump.
<Setter.Value> <ControlTemplate TargetType="{x:Type TextBoxBase}"> <Border Name="Border" CornerRadius="1" Padding="2" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="1"> <Border Name="ErrorContainer"> <ScrollViewer Margin="0" x:Name="PART_ContentHost" Background="Transparent"/> </Border> </Border> <ControlTemplate.Triggers> <Trigger Property="IsEnabled" Value="False"> <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}"/> <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}"/> </Trigger> <Trigger Property="Validation.HasError" Value="true"> <Setter TargetName="PART_ContentHost" Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=(Validation.Errors)[0].ErrorContent}" /> <Setter TargetName="ErrorContainer" Property="Padding" Value="0,0,18,0" /> <Setter TargetName="ErrorContainer" Property="Background"> <Setter.Value> <ImageBrush ImageSource="pack://application:,,,/Resources/images/error_16.png" Stretch="None" AlignmentX="Right" AlignmentY="Center" /> </Setter.Value> </Setter> </Trigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style>
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