TextBlock MultiBinding throws exception

Question

A TextBlock, should only be visible if a CheckBox is checked (x:Name=DisplaySubscriber) or the Binding string is not null or empty.

This is my approach:

<CheckBox Content="Display Subscriber" x:Name="DisplaySubscriber" />

<TextBlock Text="{Binding Path=SubscriberString, Mode=OneWay}" >
        <TextBlock.Visibility>
            <MultiBinding>
                <Binding ElementName="DisplaySubscriber" Path="IsChecked" Mode="OneWay" Converter="{StaticResource BooleanToVisibleConverter}"/>                        
                <Binding Path="SubscriberString" Mode="OneWay" Converter="{StaticResource StringIsNullEmptyConverter}"/>    
            </MultiBinding>
        </TextBlock.Visibility>
</TextBlock>

But I got this error:

Provide value on 'System.Windows.Data.MultiBinding' threw an exception.

Answer 1

converter:

public class TextBlockVisibilityConverter : IMultiValueConverter
{
    #region IMultiValueConverter Members

    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if((value[0] != null && (bool)value[0]) || (value[1]!=null && !String.IsNullOrEmpty(value[1].ToString())))
        {
            return Visibility.Visible;
        }    
        return Visibility.Collapsed;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        return null;
    }
    #endregion
}

xaml: define the converter in resource:

<local:TextBlockVisibilityConverter x:Key="TextBlockVisibilityConverter"/>

use it in the multibinding

<MultiBinding Converter="{StaticResource TextBlockVisibilityConverter}">
                <Binding ElementName="DisplaySubscriber" Path="IsChecked"/>                        
                <Binding Path="SubscriberString" />    
</MultiBinding>