【WPF】转换器Converter

作用：完成源值和绑定目标的值之间的转换

Convert:将原值转换为绑定目标的值。数据绑定引擎在将该值从源绑定传播到绑定目标时会调用到此方法

ConvertBack：将绑定目标值转换为源绑定值

值转换器：实现 IValueConverter 接口

    <Window.Resources>
        <local:Converter x:Key="convert"/>
    </Window.Resources>
    <StackPanel Orientation="Vertical">
        <TextBlock Text="0" x:Name="_text1" FontSize="50"/>
        <TextBlock Text="{Binding Path=Text,ElementName=_text1,Converter={StaticResource convert}}" FontSize="50"/>
        <TextBlock Text="1" x:Name="_text2" FontSize="50"/>
        <TextBlock Text="{Binding Path=Text,ElementName=_text2,Converter={StaticResource convert}}" FontSize="50"/>
    </StackPanel>

    public class Converter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            if (value == null) return null;
            return value.ToString() == "0" ? "Yes" : "No";
        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }

 多值转换器：实现IMultiValueConverter

    <Window.Resources>
        <local:Converter x:Key="convert"/>
    </Window.Resources>
    <StackPanel Orientation="Vertical">
        <Slider x:Name="_sliderR" Minimum="0" Maximum="255" Width="200"  Height="30" Margin="10"/>
        <Slider x:Name="_sliderG" Minimum="0" Maximum="255" Width="200"  Height="30" Margin="10"/>
        <Slider x:Name="_sliderB" Minimum="0" Maximum="255" Width="200"  Height="30" Margin="10"/>
        <Path HorizontalAlignment="Center">
            <Path.Data>
                <EllipseGeometry RadiusX="50" RadiusY="50" Center="100,100"/>
            </Path.Data>
            <Path.Fill>
                <MultiBinding Converter="{StaticResource convert}">
                    <Binding ElementName="_sliderR" Path="Value"/>
                    <Binding ElementName="_sliderG" Path="Value"/>
                    <Binding ElementName="_sliderB" Path="Value"/>
                </MultiBinding>
            </Path.Fill>
        </Path>
    </StackPanel>

    public class Converter : IMultiValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            if (values == null || values.Length < 3) return null;
            return new SolidColorBrush(Color.FromRgb(System.Convert.ToByte(values[0]), System.Convert.ToByte(values[1]), System.Convert.ToByte(values[2])));
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }