基于标签内容中未知索引处的字符的 WPF 标签样式触发器，是否可能? [英] WPF Label Style Trigger based on a char at unknown index in Contents of the Label, is it possible?

问题描述

当表单上的字段要求发生变化时，与其以编程方式设置样式，不如使用触发器来检查 Label.Contents 中的最后一个字符是否为*"，如果是，则在标签?

Rather than programatically set the the style when the requirement of a field on a form changes is it possible to use a trigger that checks the last char in a Label.Contents is a '*' and if so set a property on the Label?

类似这样，但如何检查 Content 属性的最后一个字符?

Something like this but how to check on the last char of the Content property?

  <Style x:Key="LabelStandard" TargetType="Label">
    <Setter Property="HorizontalAlignment"      Value="Left"/>
    <Setter Property="VerticalAlignment"        Value="Top"/>
    <Style.Triggers>
        <Trigger Property="Content" Value="*"> <!-TODO only check the last char -->
            <Setter Property="Foreground"      Value="Red"/>
        </Trigger>
    </Style.Triggers>
  </Style>

推荐答案

我认为您必须为此使用转换器.尝试这样的事情

I think you'll have to use a Converter for that. Try with something like this

<Style x:Key="LabelStandard" TargetType="Label">
    <Setter Property="HorizontalAlignment"      Value="Left"/>
    <Setter Property="VerticalAlignment"        Value="Top"/>
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource self},
                                       Path=Content,
                                       Converter={StaticResource LastCharConverter},
                                       ConverterParameter=*}"
                     Value="True">
            <Setter Property="Foreground" Value="Red"/>
        </DataTrigger>
    </Style.Triggers>
</Style>

public class LastCharConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        if (value == null)
        {
            return false;
        }
        string content = value.ToString();
        if (content.Length > 0 &&
            content[content.Length - 1] == (char)parameter)
        {
            return true;
        }
        return false;
    }
    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

更新

您可以绑定到 Content 字符串中的任何给定字符，只要您知道它的位置.

You can bind to any given character in the Content string as long as you know its position.

<Style x:Key="LabelStandard" TargetType="Label">
    <Setter Property="HorizontalAlignment"      Value="Left"/>
    <Setter Property="VerticalAlignment"        Value="Top"/>
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource self},
                                       Path=(Content)[2]}"
                        Value="*">
            <Setter Property="Foreground" Value="Red"/>
        </DataTrigger>
    </Style.Triggers>
</Style>

但是，如果您的字符串长度会有所不同(我认为是这种情况)，那对您没有多大好处，因为您无法在绑定中绑定 [2](以任何方式)我知道).

But if your string length will vary (which I assume is the case) that won't do you much good since you can't bind the [2] inside the binding (in any way that I'm aware of).

除此之外，我认为您必须像您自己指出的那样在解决方案背后编写代码

Other than this, I think you'll have to do a code behind solution as you pointed out yourself

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