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>

BooleanToVisibilityConverterMarkupExtension

public class BooleanToVisibilityConverterMarkupExtension : MarkupExtension, IValueConverter
{
    private static BooleanToVisibilityConverterMarkupExtension converter;

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
       return converter ?? (converter = new BooleanToVisibilityConverterMarkupExtension());
    }

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var v = (bool?)value;
        return v.HasValue && v.Value ? Visibility.Visible : Visibility.Collapsed;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var v = (Visibility)value;
        return v == Visibility.Visible;
    }
}
 
<!-- usage in xaml -->
Visibility="{Binding IsVisible, Converter={converters:BooleanToVisibilityConverterMarkupExtension}}">>