WPF中如何为绑定List的字符串大写字符设置不同字号

方案一：使用 IValueConverter 生成带格式的 InlineCollection #

利用 TextBlock 的 Inlines 属性可接受 InlineCollection 的特性，通过转换器将设备名字符串拆分为多个 Run 对象，分别为大写、小写字符设置不同字号。

转换器代码

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Data;
using System.Windows.Documents;

public class StringToMixedCaseInlinesConverter : IValueConverter
{
    // 可通过XAML绑定自定义字号
    public double UpperCaseFontSize { get; set; } = 14;
    public double LowerCaseFontSize { get; set; } = 12;

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value is not string deviceName) return DependencyProperty.UnsetValue;

        var inlines = new InlineCollection();
        foreach (char c in deviceName)
        {
            var run = new Run(c.ToString());
            run.FontSize = char.IsUpper(c) ? UpperCaseFontSize : LowerCaseFontSize;
            // 如需额外样式（如加粗）可在此扩展
            inlines.Add(run);
        }
        return inlines;
    }

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

XAML 使用示例

先在资源中声明转换器：

<Window.Resources>
    <local:StringToMixedCaseInlinesConverter x:Key="MixedCaseConverter" 
                                             UpperCaseFontSize="14" 
                                             LowerCaseFontSize="12"/>
</Window.Resources>

然后在 ComboBox 的 ItemTemplate（或自定义 ControlTemplate 的内容区域）中使用：

<ComboBox ItemsSource="{Binding AudioDevices}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock>
                <TextBlock.Inlines>
                    <Binding Path="DeviceName" Converter="{StaticResource MixedCaseConverter}"/>
                </TextBlock.Inlines>
            </TextBlock>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>

方案二：使用附加属性实现灵活绑定 #

通过自定义附加属性，直接为 TextBlock 注入大小写区分的文本样式，无需手动处理 Inlines 绑定逻辑。

附加属性代码

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;

public static class TextBlockHelper
{
    public static readonly DependencyProperty MixedCaseTextProperty =
        DependencyProperty.RegisterAttached(
            "MixedCaseText",
            typeof(string),
            typeof(TextBlockHelper),
            new PropertyMetadata(null, OnMixedCaseTextChanged));

    public static readonly DependencyProperty UpperCaseFontSizeProperty =
        DependencyProperty.RegisterAttached(
            "UpperCaseFontSize",
            typeof(double),
            typeof(TextBlockHelper),
            new PropertyMetadata(14.0, OnMixedCaseTextChanged));

    public static readonly DependencyProperty LowerCaseFontSizeProperty =
        DependencyProperty.RegisterAttached(
            "LowerCaseFontSize",
            typeof(double),
            typeof(TextBlockHelper),
            new PropertyMetadata(12.0, OnMixedCaseTextChanged));

    public static string GetMixedCaseText(TextBlock obj) => (string)obj.GetValue(MixedCaseTextProperty);
    public static void SetMixedCaseText(TextBlock obj, string value) => obj.SetValue(MixedCaseTextProperty, value);

    public static double GetUpperCaseFontSize(TextBlock obj) => (double)obj.GetValue(UpperCaseFontSizeProperty);
    public static void SetUpperCaseFontSize(TextBlock obj, double value) => obj.SetValue(UpperCaseFontSizeProperty, value);

    public static double GetLowerCaseFontSize(TextBlock obj) => (double)obj.GetValue(LowerCaseFontSizeProperty);
    public static void SetLowerCaseFontSize(TextBlock obj, double value) => obj.SetValue(LowerCaseFontSizeProperty, value);

    private static void OnMixedCaseTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is not TextBlock textBlock) return;

        textBlock.Inlines.Clear();
        var text = GetMixedCaseText(textBlock);
        if (string.IsNullOrEmpty(text)) return;

        double upperSize = GetUpperCaseFontSize(textBlock);
        double lowerSize = GetLowerCaseFontSize(textBlock);

        foreach (char c in text)
        {
            var run = new Run(c.ToString());
            run.FontSize = char.IsUpper(c) ? upperSize : lowerSize;
            textBlock.Inlines.Add(run);
        }
    }
}

XAML 使用示例

<TextBlock local:TextBlockHelper.MixedCaseText="{Binding DeviceName}"
           local:TextBlockHelper.UpperCaseFontSize="14"
           local:TextBlockHelper.LowerCaseFontSize="12"/>

关于之前转换器失败的可能原因 #

你之前的转换器大概率是返回了拆分后的字符串集合（而非 InlineCollection），或错误绑定到了 TextBlock.Text 属性（该属性仅接受纯文本，无法识别富文本格式）。上述两种方案均直接操作 Inlines 集合，可解决该问题。

内容的提问来源于stack exchange，提问作者MERUN KUMAR MAITY