封装WPF中转换器常用用法封装

• 代码经常碰到范例A转换到范例C，但是已经写好范例A转换到范例B、范例B转换范例C。通常碰到这种环境，通常会重新写过一个转换器来举行满足需求。以下是办理该痛点。
  

1. /// <summary>
2. /// 转换器组转换器
3. /// </summary>
4. [ContentProperty(nameof(Converters))]
5. public class ValueConverterGroup : IValueConverter
6. {
7.     public List<IValueConverter> Converters { get; set; } = new List<IValueConverter>();
8.     public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
9.     {
10.         if (this.Converters is IEnumerable<IValueConverter> converters)
11.         {
12.             return converters.Aggregate(value, (current, converter) => converter.Convert(current, targetType, parameter, culture));
13.         }
14.         return DependencyProperty.UnsetValue;
15.     }
17.     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
18.     {
19.         if (this.Converters is IEnumerable<IValueConverter> converters)
20.         {
21.             return converters.Reverse().Aggregate(value, (current, converter) => converter.ConvertBack(current, targetType, parameter, culture));
22.         }
23.         return DependencyProperty.UnsetValue;
24.     }
25. }

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1.         <local:ValueConverterGroup x:Key="StringToVisibilityConvert">
2.             <local:StringToUpperConvert />
3.             <local:StringToVisibilityConvert />
4.         </local:ValueConverterGroup>

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• 使用MarkupExtension举行封装转换器
  

1.     public abstract class ValueConverterBase : MarkupExtension, IValueConverter
2.     {
3.         public abstract object Convert(object value, Type targetType, object parameter, CultureInfo culture);
4.         public virtual object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
5.         {
6.             return Binding.DoNothing;
7.         }
8.         public override object ProvideValue(IServiceProvider serviceProvider)
9.         {
10.             return this;
11.         }
12.     }

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使用该类封装StringToUpperConvert

1.         //使用： <TextBlock Text="{Binding TestText, Mode=OneWay, UpdateSourceTrigger=PropertyChanged, Converter={local:StringToUpperConvert}}" />
2.     public class StringToUpperConvert : ValueConverterBase
3.     {
4.         public override object Convert(object value, Type targetType, object parameter, CultureInfo culture)
5.         {
6.             if (value is not null && value is string)
7.             {
8.                 return ((string)value).ToUpper();
9.             }
10.             return Binding.DoNothing;
11.         }
12.     }

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3.转换器单例

1.     //使用：<TextBlock Text="{Binding TestText, Converter={x:Static local:StringToUpperConvert.Instance}}" />
2.    public class StringToUpperConvert : IValueConverter
3.    {
4.        public static StringToUpperConvert Instance { get;set; } = new StringToUpperConvert();
6.        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
7.        {
8.            if (value is not null && value is string)
9.            {
10.                return ((string)value).ToUpper();
11.            }
12.            return Binding.DoNothing;
13.        }
14.        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
15.        {
16.            return DependencyProperty.UnsetValue;
17.        }
18.    }

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