Question

So I’m trying to do something along this example: http://www.codeproject.com/KB/WPF/wpfvalidation.aspx

My Textbox currently looks like this:

<TextBox Height="23" HorizontalAlignment="Left" Margin="118,60,0,0" Name="CreateUserCPRTextbox" VerticalAlignment="Top" Width="120"  >
                <TextBox.Text>

                    <Binding Path="Name" UpdateSourceTrigger="LostFocus">
                        <Binding.ValidationRules>
                            <validators:TextRangeValidator
                        MinimumLength="10"
                        MaximumLength="10"
                        ErrorMessage="ID has to be 10 letters" />
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>

            </TextBox>

I’ve directly copied my TextRangeValidator from the example on that website. Nothing happens when I lose focus on the textbox. No matter what I type in it. Any Ideas? 🙂

Answer 1

Have you set the Validation.ErrorTemplate? It is defined as below in the Application.Resources in the example.You may have missed that

<Application.Resources>

        <Style TargetType="{x:Type TextBox}">
            <Setter Property="Validation.ErrorTemplate">
                <Setter.Value>
                    <ControlTemplate>
                        <DockPanel LastChildFill="True">

                            <TextBlock DockPanel.Dock="Right"
                                Foreground="Orange"
                                Margin="5" 
                                FontSize="12pt"
                                Text="{Binding ElementName=MyAdorner, 
                           Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">
                            </TextBlock>

                            <Border BorderBrush="Green" BorderThickness="3">
                                <AdornedElementPlaceholder Name="MyAdorner" />
                            </Border>

                        </DockPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <Style.Triggers>
                <Trigger Property="Validation.HasError" Value="true">
                    <Setter Property="ToolTip"
                        Value="{Binding RelativeSource={RelativeSource Self}, 
                   Path=(Validation.Errors)[0].ErrorContent}"/>
                </Trigger>
            </Style.Triggers>
        </Style>

    </Application.Resources>

EDIT

Your default value is not triggering the validation routine.To force it to validate for default value you have to set

<validators:TextRangeValidator ValidatesOnTargetUpdated="True"
                        MinimumLength="10"
                        MaximumLength="10"
                        ErrorMessage="ID has to be 10 letters" />