Converter to toggle visibility when content is empty #wpdev #wp8dev #wp7dev #win8dev

Recently Gustavo Guerra posted a question on StackOverflow.com stating that behaviour of TextBlock was different on Windows Phone 7 and Windows Phone 8. If the Text is empty, WP7 renders TextBlock with Height set to 0. On WP8, it occupies full height.

I replied back stating that he should consider using a Converter for the same. Of course I had a similar issue with Cineworld app. The screenshot shows ratings & review screen I implemented – its almost a copy of Windows Phone Store ratings & review.

what I noticed was that if user chose to not review it, the textbox would be fully render. So I did what I suggested Gustavo do. Created two converters – StringLengthInvisibilityConverter and StringLengthVisibilityConverter. Almost identical but doing the opposite thing.

 

public class StringLengthInvisibilityConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string itemVal = value as String;
        if (String.IsNullOrWhiteSpace(itemVal))
            return Visibility.Collapsed;
        else
            return Visibility.Visible;
    }

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

public class StringLengthVisibilityConverter : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string itemVal = value as String;
        if (String.IsNullOrWhiteSpace(itemVal))
            return Visibility.Visible;
        else
            return Visibility.Collapsed;
    }

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

<TextBlock Text="{Binding Review}" Visibility="{Binding Review, Converter={StaticResource InvisibilityConverter}}" TextWrapping="Wrap" Style="{StaticResource PhoneTextNormalStyle}" Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="2"/>
<TextBlock Text="(rating only)" Visibility="{Binding Review, Converter={StaticResource VisibilityConverter}}" Foreground="{StaticResource PhoneSubtleBrush}" TextWrapping="Wrap" Style="{StaticResource PhoneTextNormalStyle}" Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="2"/>

 

Now I know one of you clever person is going to tell me I could have just used one 😛 Let me tell you this:

1. I thought of it
2. I could have searched around
3. Realised no one really cares
4. Created two converters and got the job done 🙂
5. Submitted update and nap time

.

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