Formatting a Data Bound TimeSpan on WP7

Today, I was attempting to format a data bound TimeSpan for our upcoming application using the Custom TimeSpan Format Strings provided on MSDN

Much to my surprise, no matter what I tried, it didn’t appear to format the text, and I’m not the only one to find this.

TimeSpan ts = TimeSpan.FromSeconds(1.24);
string st = string.Format(@"{0:hh\:mm\:ss}", dt);
// st = "00:00:01.2400000"

Clearly the seconds formatting is not working correctly.  And worse, the documentation states that the time separators are not placeholders.

In my case, I know my TimeSpan is always less than 24 hours, so I thought the best solution was to convert it to a DateTime using a converter.

public class TimespanToDateTimeConverter : IValueConverter
{
  public object Convert(object value, Type targetType, 
      object parameter, CultureInfo culture)
  {
    return new DateTime(((TimeSpan) value).Ticks);
  }

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

Now in my xaml, I do this to bind to an object named Elapsed:

 

<Grid>
  <Grid.Resources>
    <fwk:TimespanToDateTimeConverter x:Key="asDate" />
  </Grid.Resources>  ...
  <TextBlock Text="{Binding Elapsed, 
      Converter={StaticResource asDate}, 
      StringFormat='{0:HH\:mm\:ss\}'}" />

</Grid>

This neatly solves the problem, and in the process, delivers locale specific separators as well.