WPF 可见性绑定到具有多个变量的布尔表达式

Question

我有两个布尔值，我想根据它们的值显示 Image，如下所示：

   <Window.Resources>
    <BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter"/>
</Window.Resources>

<Image Visibility="{Binding (Boolean1 && Boolean2),Converter={StaticResource BooleanToVisibilityConverter}}" />

注意 Boolean1 和 Boolean2 表达式。

Answer 1

XAML 中没有定义&& 运算符，但您可以绑定到多个属性并使用IMultiValueConverter：

<Image>
    <Image.Visibility>
        <MultiBinding Converter="{StaticResource YourMultiConverter}">
            <Binding Path="Boolean1" />
            <Binding Path="Boolean2" />
        </MultiBinding>
    </Image.Visibility>
</Image>

---

public class YourMultiValueConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool a = (bool)values[0];
        bool b = (bool)values[1];

        return a && b ? Visibility.Visible : Visibility.Collapsed;
    }

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

或者您可以使用带有条件的Image 样式：

<Image>
    <Image.Style>
        <Style TargetType="Image">
            <Setter Property="Visibility" Value="Collapsed" />
            <Style.Triggers>
                <MultiDataTrigger>
                    <MultiDataTrigger.Conditions>
                        <Condition Binding="{Binding Boolean1}" Value="True" />
                        <Condition Binding="{Binding Boolean2}" Value="True" />
                    </MultiDataTrigger.Conditions>
                    <Setter Property="Visibility" Value="Visible" />
                </MultiDataTrigger>
            </Style.Triggers>
        </Style>
    </Image.Style>
</Image>

Answer 2

mm8 提供了正确的答案，但是会有一点改进

public class LogicalAndConverter : IMultiValueConverter
{
    public IValueConverter FinalConverter{get;set;}

    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        bool rtn = values.All(v=>(bool)v);

        if(FinalConverter==null)    
            return rtn;
        else
            return FinalConverter.Convert(rtn,targetType,parameter,culture);
    }

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

这允许您使用不同的转换器而无需重写多转换器

<local:LogicalAndConverter x:Key="LogicalAndConverter ">
    <local:LogicalAndConverter.FinalConverter>
        <BooleanToVisibilityConverter />
    </local:LogicalAndConverter.FinalConverter>
</local:LogicalAndConverter>

Answer 3

如果您不介意在您的项目中添加另一个包，DevExpress 的 MVVM 框架（可免费获得）有一个名为 DXBinding 的绑定标记扩展，允许您编写绑定函数/表达式。

<Image Visibility="{DXBinding 'Boolean1 and Boolean2', Converter={StaticResource BooleanToVisibilityConverter}}"/>

Answer 4

你可以使用多值转换器来解决这个问题

XAML：

 <TextBlock Name="textBlockOutput" Grid.Row="4" Grid.Column="2">
        <TextBlock.Text>
            <MultiBinding Converter="{StaticResource MultiValueConverter}">
                <Binding Path="TextOne" />
                <Binding Path="TextTwo" />
                <Binding Path="TextThree" />
            </MultiBinding>
        </TextBlock.Text>
    </TextBlock>




 public class MultiValueConverter : IMultiValueConverter
{
    public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
    {
        string one = values[0] as string;
        string two = values[1] as string;
        string three = values[2] as string;
        if(!string.IsNullOrEmpty(one) && !string.IsNullOrEmpty(two) && !string.IsNullOrEmpty(three))
        {
            return one + two + three;
        }
        return null;
    }

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