Converter

Built-in converter

BooleanToVisibilityConverter

BooleanToVisibilityConverter is located in System.Windows.Controls.

<Window> <Window.Resources> <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" /> </Window.Resources> <TextBlock Visibility="{Binding IsVisible, Converter={StaticResource BooleanToVisibilityConverter}}" />

ValueConverter

<UserControl xmlns:conversion="clr-namespace:MyNamespace.Conversion"> <UserControl.Resources> <conversion:ListToVisibilityConverter x:Key="ListToVisibilityConverter" /> </UserControl.Resources> <TextBlock Visibility="{Binding MyList, Converter={StaticResource ListToVisibilityConverter}}" />

namespace MyNamespace.Conversion { // L'attribut ValueConversion est optionel, // il permet de spécifier le type d'entrée et le type de sortie [ValueConversion(typeof(IEnumerable), typeof(Visibility))] public class ListToVisibilityConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { if (value is IEnumerable itemCollection) { return itemCollection.Cast<object>().Any() ? Visibility.Visible : Visibility.Collapsed; } return Visibility.Collapsed; } // Conversion inverse non-implémentée public object ConvertBack(object value, Type targetTypes, object parameter, CultureInfo culture) { throw new NotSupportedException(); throw new NotImplementedException(); return null; } } }

Inverted convertion

<TextBlock Visibility="{Binding MyProperty, Converter={StaticResource BooleanToVisibilityConverter}, ConverterParameter=Inverted}" />

BooleanToVisibilityConverter.cs

[ValueConversion(typeof(bool), typeof(Visibility))] public sealed class BooleanToVisibilityConverter : IValueConverter { public object IValueConverter.Convert(object value, Type targetType, object parameter, CultureInfo culture) { bool visibleFlag; if (value is bool b) { visibleFlag = b; } else { return DependencyProperty.UnsetValue; } if (parameter != null && Enum.TryParse(parameter.ToString(), true, out Parameters invert) && invert == Parameters.Inverted) { visibleFlag = !visibleFlag; } return visibleFlag ? Visibility.Visible : Visibility.Collapsed; } public object IValueConverter.ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { throw new NotSupportedException(); } private enum Parameters { Normal, Inverted }

MultiValueConverter

<UserControl xmlns:conversion="clr-namespace:MyNamespace.Conversion"> <UserControl.Resources> <conversion:TakeItemsConverter x:Key="TakeItemsConverter"/> </UserControl.Resources> <ItemsControl> <ItemsControl.ItemsSource> <MultiBinding Converter="{StaticResource TakeItemsConverter}"> <Binding Path="Items" /> <Binding Path="MaxNumberOfItemsToDisplay" /> </MultiBinding> </ItemsControl.ItemsSource> </ItemsControl>

namespace MyNamespace.Conversion { // L'attribut ValueConversion n'est pas utilisé ici car il n'est pas adapté // au MultiValueConverter : il ne peut définir qu'un seul type d'entrée public class TakeItemsConverter : IMultiValueConverter { public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture) { // expect 2 values, an IEnumerable and an int if (values != null && values.Length == 2 && values[0] is IEnumerable itemCollection && values[1] != null && int.TryParse(values[1].ToString(), NumberStyles.Integer, culture, out var numberOfItemsToTake)) { return itemCollection.Cast<object>().Take(numberOfItemsToTake); } return DependencyProperty.UnsetValue; } // Conversion inverse non-implémentée public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture) { throw new NotImplementedException(); } } }