Binding常用辅助属性、多重绑定、优先级绑定

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Binding常用辅助属性、多重绑定、优先级绑定

Binding常用辅助属性

StringFormat

<Window.Resources>
    <sys:Int32 x:Key="myInt">200</sys:Int32>
    <sys:Single x:Key="mySingle">100.123456</sys:Single>
</Window.Resources>
<StackPanel>
    <!--货币-->
    <TextBlock Text="{Binding Source={StaticResource myInt}, StringFormat={}{0:C}}"/>
    <!--中文货币符号-->
    <TextBlock Text="{Binding Source={StaticResource myInt}, StringFormat={}{0:C} ,ConverterCulture=zh-CN}"/>
    <!--文字拼接-->
    <TextBlock Text="{Binding Source={StaticResource myInt}, StringFormat=单价{0:C} ,ConverterCulture=zh-CN}"/>
    <!--数字-->
    <TextBlock Text="{Binding Source={StaticResource mySingle}, StringFormat={}{0:F2}}"/>
    <!--时间-->
    <TextBlock Text="{Binding Path=DateTimeDateTime,  RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=Window}, StringFormat={}{0:yyyy-MM-dd HH:mm:ss}}"/>
</StackPanel>

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FallbackValue :bingding无法返回值时所显示的默认值
TargetNullValue:当绑定源为null时绑定目标所显示的值
Delay:从绑定目标修改到绑定源更新的延迟时间

多重绑定

当需要的信息不止一个数据源时可以使用MultiBindingMultiBinding具有一个Bindings的属性类型是Collection处在这个集合中的Binding对象可以拥有自己的数据校验和转换机制他们汇总起来的数据将传递到Target上。

public class Data
{
    private int _value1 =2;

    public int Value1
    {
        get { return _value1; }
        set { _value1 = value; }
    }

    private int _value2 =2;

    public int Value2
    {
        get { return _value2; }
        set { _value2 = value; }
    }

    // 有些情况数据需要进行计算得到一个新的结果 
    private int _value3;

    public int Value3
    {
        get { return Value1 + Value2; }
        set { _value3 = value; }
    }

}

在XAML中使用多重绑定

<!--MultiBinding-->
<TextBlock>
    <TextBlock.Text>
        <MultiBinding StringFormat="{}{0}-{1}-{2}">
            <Binding Path="Value1"/>
            <Binding Path="Value2"/>
            <Binding Path="Value3" FallbackValue="异常"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

另一种实现方式

<!--两一种实现方式-->
<TextBlock>
    <Run Text="{Binding Value1}"/><Run Text="{Binding Value2 ,StringFormat=-{0}}"/><Run Text="{Binding Value3 ,StringFormat=-{0}}"/>
</TextBlock>

使用IMultiValueConverter

// 多重绑定值转换器
public class MyValueConverter : IMultiValueConverter
{
    /// <summary>
    /// 从源到目标
    /// </summary>
    /// <param name="values">数组绑定的所有值</param>
    /// <param name="targetType">目标控件的目标属性</param>
    /// <param name="parameter"></param>
    /// <param name="culture"></param>
    /// <returns></returns>
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        return values[0].ToString() +"-"+ values[1].ToString() +"-IMultiValueConverter";
    }

    /// <summary>
    /// 从目标到源
    /// </summary>
    /// <param name="value">单值</param>
    /// <param name="targetTypes">类型数组</param>
    /// <param name="parameter"></param>
    /// <param name="culture"></param>
    /// <returns>返回数组</returns>
    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
    {
        return null;
    }
}

<TextBlock>
    <TextBlock.Text>
        <MultiBinding Converter="{StaticResource myConverter}">
            <Binding Path="Value1"/>
            <Binding Path="Value2"/>
        </MultiBinding>
    </TextBlock.Text>
</TextBlock>

多重绑定转换器的详细说明参见5-3Binding对数据的转换和校验

三种方式的展示效果

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优先级绑定

绑定是确定优先顺序

public class Data
{
    private int _value1 = 1;

    public int Value1
    {
        get
        {
            Thread.Sleep(10000);// 耗时操作
            return _value1;
        }
        set { _value1 = value; }
    }

    private int _value2 = 2;

    public int Value2
    {
        get
        {
            Thread.Sleep(8000);// 耗时操作
            return _value2;
        }
        set { _value2 = value; }
    }

    private int _value3 = 3;

    public int Value3
    {
        get
        {
            Thread.Sleep(5000);// 耗时操作
            return _value3;
        }
        set { _value3 = value; }
    }
}

XAML

<TextBox>
    <PriorityBinding FallbackValue="正在获取数据...">
        <!--并不是全部显示 而是以优先级顺序来显示-->
        <Binding Path="Value1" IsAsync="True" UpdateSourceTrigger="PropertyChanged"/>
        <Binding Path="Value2" IsAsync="True" UpdateSourceTrigger="PropertyChanged"/>
        <Binding Path="Value3" IsAsync="True" UpdateSourceTrigger="PropertyChanged"/>
    </PriorityBinding>
</TextBox>