Question

所以我试图在我的Viewmodel（Enum和Strings的混合）上将TextBlock绑定到多个值。当转换器返回文本为null时，我有一个假定的DataTrigger。但事实并非如此！起初，我认为我的风格没有抓住（因此改变了风格的背景以表明它的确如此）。无论如何这里是代码

XAML

<TextBlock x:Name="MyTextBlock" Grid.Column="2" Grid.ColumnSpan="3"  VerticalAlignment="Center" DataContext="{StaticResource ViewModelLocator}"
                   Margin="{Binding RelativeSource={RelativeSource Self}, Path=(params:General.BoldPadding), Mode=OneWay}">

            <TextBlock.Text>
                <MultiBinding Converter="{StaticResource GeneralMultiStringDisplayConverter}">
                    <Binding Path="RatesViewModel.Instrument.Currency" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
                    <Binding Path="RatesViewModel.Instrument.Underlying" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
                    <Binding Path="RatesViewModel.Instrument.ProductType" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
                </MultiBinding>
            </TextBlock.Text>
            <TextBlock.Resources>
                <Style TargetType="{x:Type TextBlock}" BasedOn="{StaticResource HeaderTextStyle}">
                    <Setter Property="Background" Value="Blue"/>
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding ElementName=MyTextBlock, Path=Text}" Value="{x:Null}"> <!--THIS SHOULD FIRE-->
                            <Setter Property="Text" Value="ThisShouldFireOnStart"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </TextBlock.Resources>
        </TextBlock>

转换器如下：

class GeneralMultiStringDisplayConverter:IMultiValueConverter
{

    public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        var AS = DependencyProperty.UnsetValue;    
        if (values[0] != AS )
        {
            int count = values.Count();
            string result = string.Empty;
            for (int i = 0; i < count - 1; ++i)
            {
                try
                {
                    var A = Enum.GetName((values[i].GetType()), values[i]);
                    result = String.Format("{0}{1}.", result, A);
                }
                catch (Exception ex)
                {

                    result = String.Format("{0}{1}.", result, values[i]);
                }
            }
            result = String.Format("{0}{1}", result, values[count - 1]);
            return result;
        }
        return null;
    }

    public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
    {
        return null;
        //TODO:
    }
}

调试我已采取的步骤

    `<Setter Property="Text" Value="ABC"/>
         <Style.Triggers>
<DataTrigger Binding="{Binding ElementName=MyTextBlock, Path=Text}" Value="ABC"> 
<Setter Property="Text" Value="ThisShouldFireOnStart"/>
 </DataTrigger>
   </Style.Triggers>
                           `

在Styles DataTrigger绑定中添加了转换器。它总是将“”作为参数，并且由于某种原因不是null。将触发器值设置为“”不起作用。
在样式中添加了默认的Text属性，并尝试更改基于该值的值。（见上面的例子）

我希望得到一些帮助，让这个工作谢谢！

Answer 1

您无法使用Style中的DataTrigger覆盖这些本地绑定。见Why doesn’t my WPF Trigger work?

如果您只需要显示字符串，如果您的绑定为null，请使用TargetNullValue="MyNullValueString"

也许您需要在转换器中使用if(value[0] != null)条件来识别未设置的属性。由于我没有您的RatesViewModel的任何细节，我无法肯定地说。

<MultiBinding Converter="{StaticResource GeneralMultiStringDisplayConverter}" TargetNullValue="ThisIsNull">
    <Binding Path="RatesViewModel.Instrument.Currency" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
    <Binding Path="RatesViewModel.Instrument.Underlying" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
    <Binding Path="RatesViewModel.Instrument.ProductType" NotifyOnSourceUpdated="True" UpdateSourceTrigger="PropertyChanged"/>
</MultiBinding>

多值绑定文本块DataTrigger未触发

1 个答案: