C# – WPF DataBinding: Nullable Int still gets a validation error

cdata-bindingvalidationwpf

I have a textbox databound to a nullable int through code. If I erase the data from the textbox it gives me a validation error (red border around it).

Here is my binding code:

ZipBinding = new Binding("Zip");
ZipBinding.Source = Address;
zipTextBox.SetBinding(TextBox.TextProperty, ZipBinding);

public Int32? Zip { get { ... } set { ... } }

It's clearly marked as a Nullable so why does WPF wanna give me a validation issue when I clear the textbox?

Best Answer

Validation is failing because it can't convert the empty string to a nullable integer. Set TargetNullValue to string.empty on the Binding and it will convert the empty string to null, which will be valid.

Related Solutions

C# – How to get rid of the red rectangle when the wpf binding validation has failed and the containing panel is no longer visible

If I remember correctly, this is a known issue. We re-templated textbox to include the following:

<Setter Property="Validation.ErrorTemplate">
    <Setter.Value>
        <ControlTemplate>
            <ControlTemplate.Resources>
                <BooleanToVisibilityConverter x:Key="converter" />
        </ControlTemplate.Resources>
            <DockPanel LastChildFill="True">
                <Border 
                    BorderThickness="1"
                    BorderBrush="Red"
                    Visibility="{Binding ElementName=placeholder, Mode=OneWay, Path=AdornedElement.IsVisible, Converter={StaticResource converter}}">
                    <AdornedElementPlaceholder x:Name="placeholder" />
                </Border>
             </DockPanel>
         </ControlTemplate>
    </Setter.Value>
</Setter>

Wpf – Show the validation error template on a different control in WPF

to accomplish this task I've used this solution. It uses converter, that "hides" border by converting (Validation.Errors).CurrentItem to Thickness.

<Grid>
    <Grid.Resources>
        <data:ValidationBorderConverter
            x:Key="ValidationBorderConverter" />
    </Grid.Resources>
    <Border
        BorderBrush="#ff0000"
        BorderThickness="{Binding 
            ElementName=myControl, 
            Path=(Validation.Errors).CurrentItem, 
            onverter={StaticResource ValidationBorderConverter}}">
        <TextBox
            ToolTip="{Binding 
                ElementName=myControl, 
                Path=(Validation.Errors).CurrentItem.ErrorContent}" />
    </Border>
</Grid>

ValidationBorderConverter class is pretty simple:

[ValueConversion(typeof(object), typeof(ValidationError))]
public sealed class ValidationBorderConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, 
            System.Globalization.CultureInfo culture)
    {
        return (value == null) ? new Thickness(0) : new Thickness(1);
    }

    public object ConvertBack(object value, Type targetType, object parameter, 
            System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

Best Answer

Related Solutions

C# – How to get rid of the red rectangle when the wpf binding validation has failed and the containing panel is no longer visible

Wpf – Show the validation error template on a different control in WPF

Related Topic