XAML Developer Chips: Composite Converters
The article will be devoted to a simple but effective pattern - Composite Converter [a composite converter ].
There are situations when there are already several converters, but there is a need to create a new one, which is a logical composition of the existing ones. In order not to create classes that partly duplicate the functionality, you can do the following. Note the PostConverter and PostConverterParameter properties .
This will allow converters into logical chains of various lengths and easily build new ones on the basis of existing ones.
Brilliant simple! Use on health!
Live samples are available from the Aero Framework library [ backup link ].
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Thank!
PS Previous article on embedded converters
There are situations when there are already several converters, but there is a need to create a new one, which is a logical composition of the existing ones. In order not to create classes that partly duplicate the functionality, you can do the following. Note the PostConverter and PostConverterParameter properties .
using System.Windows.Data; namespace Aero.Converters.Patterns { public interface ICompositeConverter : IValueConverter { IValueConverter PostConverter { get; set; } object PostConverterParameter { get; set; } } } Inline converter
using System; using System.Globalization; using System.Windows.Data; using Aero.Converters.Patterns; namespace Aero.Converters { public class InlineConverter : IInlineConverter, ICompositeConverter { public IValueConverter PostConverter { get; set; } public object PostConverterParameter { get; set; } public event EventHandler<ConverterEventArgs> Converting; public event EventHandler<ConverterEventArgs> ConvertingBack; public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { var args = new ConverterEventArgs(value, targetType, parameter, culture); var handler = Converting; if (handler != null) handler(this, args); return PostConverter == null ? args.ConvertedValue : PostConverter.Convert(args.ConvertedValue, targetType, PostConverterParameter, culture); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { var args = new ConverterEventArgs(value, targetType, parameter, culture); var handler = ConvertingBack; if (handler != null) handler(this, args); return PostConverter == null ? args.ConvertedValue : PostConverter.ConvertBack(args.ConvertedValue, targetType, PostConverterParameter, culture); } } } Switch converter
using System; using System.Globalization; using System.Linq; using System.Windows; using System.Windows.Data; using System.Windows.Markup; using Aero.Converters.Patterns; namespace Aero.Converters { [ContentProperty("Cases")] public class SwitchConverter : DependencyObject, ISwitchConverter, ICompositeConverter { public static readonly DependencyProperty DefaultProperty = DependencyProperty.Register( "Default", typeof(object), typeof(SwitchConverter), new PropertyMetadata(CaseSet.UndefinedObject)); public SwitchConverter() { Cases = new CaseSet(); } public object Default { get { return GetValue(DefaultProperty); } set { SetValue(DefaultProperty, value); } } public CaseSet Cases { get; private set; } public bool TypeMode { get; set; } public object Convert(object value, Type targetType, object parameter, CultureInfo culture) { if (TypeMode) value = value == null ? null : value.GetType(); var pair = Cases.FirstOrDefault(p => Equals(p.Key, value) || SafeCompareAsStrings(p.Key, value)); var result = pair == null ? Default : pair.Value; value = result == CaseSet.UndefinedObject ? value : result; return PostConverter == null ? value : PostConverter.Convert(value, targetType, PostConverterParameter, culture); } public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) { if (TypeMode) value = value == null ? null : value.GetType(); var pair = Cases.FirstOrDefault(p => Equals(p.Value, value) || SafeCompareAsStrings(p.Value, value)); value = pair == null ? Default : pair.Key; return PostConverter == null ? value : PostConverter.ConvertBack(value, targetType, PostConverterParameter, culture); } private static bool SafeCompareAsStrings(object a, object b) { if (a == null && b == null) return true; if (a == null || b == null) return false; return string.Compare(a.ToString(), b.ToString(), StringComparison.OrdinalIgnoreCase) == 0; } public IValueConverter PostConverter { get; set; } public object PostConverterParameter { get; set; } } } This will allow converters into logical chains of various lengths and easily build new ones on the basis of existing ones.
<Grid.Resources> <BooleanConverter x:Key="YesNoConverter" OnTrue="Yes" OnFalse="No"/> <SwitchConverter x:Key="CompositeSwitchConverter" PostConverter="{StaticResource YesNoConverter}"> <Case Key="0" Value="False"/> <Case Key="1" Value="True"/> </SwitchConverter> </Grid.Resources> <TextBlock Text="{Binding Number, Converter={StaticResource CompositeSwitchConverter}}"/> Number == 1 => out: Yes Number == 0 => out: No Brilliant simple! Use on health!
Live samples are available from the Aero Framework library [ backup link ].
')
Thank!
PS Previous article on embedded converters
Source: https://habr.com/ru/post/276273/
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