Silverlight Knowledge Base

Using the ConverterParameter

The Binding object provides an additional property, which allows you to feed a parameter to the IValueConverter. This can be useful if you want to employ a converter in several related scenarios that are slightly different. Those familiar with formatting strings in .NET should be no stranger to the variety of FormatStrings available for built-in data types. The following example leverages the ConverterParameter to provide a FormatString.

The following example passes in the .NET short date format string '{0:d}' for display of the destination's start of peak season:

// Class for converting to a string based on the provided FormatString public class FormatStringConverter : IValueConverter {

public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

string formatString = (string)parameter; return String.Format(formatString, value);

public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)

throw new NotImplementedException();

<UserControl x:Class="Wrox.Silverlight30.Data.Convertion.Page"

xmlns="http://schemas.microsoft.com/winfx/200 6/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/200 6/xaml" xmlns:data="clr-namespace:Wrox.Silverlight3 0.Data.Convertion" Width="400" Height="3 00"> <UserControl.Resources>

<data:FormatStringConverter x:Key="FormatStringConverter" /> </UserControl.Resources>

<Grid x:Name="LayoutRoot" Background="White"> <StackPanel>

<TextBlock Text="{Binding PeakSeasonStart,

Converter={StaticResource FormatStringConverter}, ConverterParameter='{0:d}'}" /> </StackPanel> </Grid> </UserControl>

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