DateTimeFormatterConverter for WinRT

With there being no StringFormat on a binding in WinRT yet you can use this converter to leverage the crazy (different) DateTimeFormatter object:

    public class DateTimeFormatterConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, string language)
        {
            var formatter = new Windows.Globalization.DateTimeFormatting.DateTimeFormatter(parameter.ToString());
            return formatter.Format((DateTime)value);
        }

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

Usage:

<converters1:DateTimeFormatterConverter x:Key="DateTimeFormatterConverter" />

<TextBlock Text="{Binding DealDate, 
                               Converter={StaticResource DateTimeFormatterConverter},
                               ConverterParameter=day month year}"

Setting format for Telerik RadDatePicker

First up remember there are two date pickers the RadDatePicker and the RadDateTimePicker.

You can specialise with your date hardcoded, or have a property that lets the developer set the value:

public class RadDatePickerWithSwissDates : RadDatePicker
{
    public RadDatePickerWithSwissDates()
    {
        var ci = new CultureInfo("")
        {
            DateTimeFormat = { ShortDatePattern = "dd.MM.yyyy" }
        };

        this.Culture = ci;
    }
}

Or you can use this approach:

public class TelerikDateFormatWorkaround
{
  public CultureInfo CultureWithSwissFormat
  {
      //Hack to get around the fact that there is no custom date format in the Telerik DatePicker
      //http://www.telerik.com/community/forums/wpf/datepicker/changing-dateformat.aspx
      get
      {
          var tempCultureInfo = (CultureInfo)CultureInfo.CurrentCulture.Clone();
          tempCultureInfo.DateTimeFormat.ShortDatePattern = "dd.MM.yyyy";
          return tempCultureInfo;
      }
  }
}

// add it to the usercontrol resources in the usual way and then...

<Style TargetType="telerik1:RadDatePicker">
   <Setter Property="Culture" Value="{Binding Source={StaticResource TelerikDateFormatWorkaround}, Path=CultureWithSwissFormat}"/>
</Style>

Silverlight DateTime converter