WPF 本地化的最佳做法

资源文件
- 英文资源文件 en-US.xaml
- 中文资源文件 zh-CN.xaml
资源使用
- App.xaml
- 主界面布局
- cs代码
App.config
辅助类
- 语言切换操作类
- 资源 binding 解析类
实现效果

应用程序本地化有很多种方式，选择合适的才是最好的。这里只讨论一种方式，动态资源（DynamicResource） 这种方式可是在不重启应用程序的情况下进行资源的切换，不论是语言切换，还是更上层的主题切换。想要运行时切换不同的资源就必须使用 动态资源（DynamicResource） 这种方式。
图片是可以使用资源字典进行动态 binding 的不要被误导了

资源文件

确保不同语言环境中资源 Key 是同一个，且对用的资源类型是相同的。
在资源比较多的情况下，可以通过格式化的命名方式来规避 Key 冲突。

资源文件的属性可以设置成：
生成操作：内容
复制到输出目录：如果较新则复制

上面的操作可以在不重新编译程序的情况下编辑语言资源并应用。

如果不想让别人更改语言资源则
生成操作：页
复制到输出目录：不复制

英文资源文件 en-US.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib">

    <sys:String x:Key="WindowsTitle">MainWindow</sys:String>
    <ImageSource x:Key="icon">pack://SiteOfOrigin:,,,/Icons/en-USicon.png</ImageSource>
    <sys:String x:Key="LanguageButton">LanguageButton</sys:String>

    <sys:String x:Key="LockTime-OneMinute">1 Minute</sys:String>
    <sys:String x:Key="LockTime-FiveMinute">5 Minute</sys:String>
    <sys:String x:Key="LockTime-TenMinute">10 Minute</sys:String>
    <sys:String x:Key="LockTime-FifteenMinute">15 Minute</sys:String>
    <sys:String x:Key="LockTime-ThirtyMinute">30 Minute</sys:String>
    <sys:String x:Key="LockTime-OneHour">1 Hour</sys:String>
    <sys:String x:Key="LockTime-TwoHour">2 Hour</sys:String>
    <sys:String x:Key="LockTime-ThreeHour">3 Hour</sys:String>
    <sys:String x:Key="LockTime-Never">Never</sys:String>
</ResourceDictionary>

中文资源文件 zh-CN.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:sys="clr-namespace:System;assembly=mscorlib">

    <sys:String x:Key="WindowsTitle">主窗口</sys:String>
    <ImageSource x:Key="icon">pack://SiteOfOrigin:,,,/Icons/zh-CNicon.png</ImageSource>
    <sys:String x:Key="LanguageButton">语言按钮</sys:String>

    <sys:String x:Key="LockTime-OneMinute">1 分钟</sys:String>
    <sys:String x:Key="LockTime-FiveMinute">5 分钟</sys:String>
    <sys:String x:Key="LockTime-TenMinute">10 分钟</sys:String>
    <sys:String x:Key="LockTime-FifteenMinute">15 分钟</sys:String>
    <sys:String x:Key="LockTime-ThirtyMinute">30 分钟</sys:String>
    <sys:String x:Key="LockTime-OneHour">1 小时</sys:String>
    <sys:String x:Key="LockTime-TwoHour">2 小时</sys:String>
    <sys:String x:Key="LockTime-ThreeHour">3 小时</sys:String>
    <sys:String x:Key="LockTime-Never">永不</sys:String>
</ResourceDictionary>

资源使用

App.xaml

设置默认语言资源，用于在设计阶段预览，并利用 VS 智能提示资源的 Key 防止 Key编写出错。

<Application
    x:Class="Localization.Core.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:Localization.Core"
    StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="/I18nResources/en-US.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

主界面布局

<Window
    x:Class="Localization.Core.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:Localization.Core"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:operate="clr-namespace:Localization.Core.Operates"
    Title="{DynamicResource WindowsTitle}"
    Width="800"
    Height="450"
    Icon="{DynamicResource icon}"
    mc:Ignorable="d">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition />
        </Grid.RowDefinitions>
        <ComboBox
            x:Name="comLan"
            Width="{Binding SizeToContent.Width}"
            Height="{Binding SizeToContent.Width}"
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            SelectedValuePath="Tag"
            SelectionChanged="ComboBox_SelectionChanged">
            <ComboBoxItem Content="中文" Tag="zh-CN" />
            <ComboBoxItem Content="English" Tag="en-US" />
        </ComboBox>

        <StackPanel Grid.Row="1">

            <Button
                Margin="0,50,0,0"
                HorizontalAlignment="Center"
                VerticalAlignment="Center"
                Content="{DynamicResource LanguageButton}" />

            <ComboBox
                x:Name="cmTime"
                Width="120"
                Margin="20"
                VerticalAlignment="Center">
                <ComboBox.ItemTemplate>
                    <DataTemplate>
                        <TextBlock Text="{operate:ResourceBinding Key}" />
                    </DataTemplate>
                </ComboBox.ItemTemplate>
            </ComboBox>
        </StackPanel>

    </Grid>
</Window>

cs代码

public partial class MainWindow : Window
{
    ObservableCollection<KeyValuePair<string, int>>? TimeList { get; set; }

    public MainWindow()
    {
        InitializeComponent();

        var lan = Thread.CurrentThread.CurrentCulture.Name;
        comLan.SelectedValue = lan;

        Loaded += MainWindow_Loaded;
    }

    private void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        TimeList = new ObservableCollection<KeyValuePair<string, int>>()
        {
            new KeyValuePair<string, int>("LockTime-OneMinute", 1),
            new KeyValuePair<string, int>("LockTime-FiveMinute", 5),
            new KeyValuePair<string, int>("LockTime-TenMinute", 10),
            new KeyValuePair<string, int>("LockTime-FifteenMinute", 15),
            new KeyValuePair<string, int>("LockTime-ThirtyMinute", 30),
            new KeyValuePair<string, int>("LockTime-OneHour", 60),
            new KeyValuePair<string, int>("LockTime-TwoHour", 120),
            new KeyValuePair<string, int>("LockTime-ThreeHour", 180),
            new KeyValuePair<string, int>("LockTime-Never", 0),
        };

        cmTime.ItemsSource = TimeList;
        cmTime.SelectedValue = TimeList[0];
    }

    private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (e.AddedItems is null) return;

        LanguageOperate.SetLanguage((e.AddedItems[0] as ComboBoxItem)!.Tag.ToString()!);
    }
}

App.config

language 配置项用于保存用户选择的语言类型

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<appSettings>
		<add key="language" value=""/>
	</appSettings>
</configuration>

辅助类

语言切换操作类

检查方法入参，有值则切换到指定的资源，无值则读取配置文件中的值，若配置文件中仍无值，则获取当前线程运行的语言环境，切换到与语言环境相匹配的资源，如果没有找到与之匹配的资源则不做操作。

切换资源之后，将配置文件中的 language 的 value 改为当前所选的语言保存并刷新配置文件，直到下次更改。

重写 Application 类的 OnStartup 方法，在 OnStartup 中调用 SetLanguage 方法以实现应用程序启动对语言环境的判别。

/// <summary>
/// 语言操作
/// </summary>
public class LanguageOperate
{
    private const string KEY_OF_LANGUAGE = "language";

    /// <summary>
    /// 语言本地化
    /// </summary>
    /// <param name="language">语言环境</param>
    public static void SetLanguage(string language = "")
    {
        if (string.IsNullOrWhiteSpace(language))
        {
            language = ConfigurationManager.AppSettings[KEY_OF_LANGUAGE]!;

            if (string.IsNullOrWhiteSpace(language))
                language = System.Globalization.CultureInfo.CurrentCulture.ToString();
        }

        string languagePath = $@"I18nResources\{language}.xaml";

        if (!System.IO.File.Exists(languagePath)) return;

        var lanRd = Application.LoadComponent(new Uri(languagePath, UriKind.RelativeOrAbsolute)) as ResourceDictionary;
        var old = Application.Current.Resources.MergedDictionaries.FirstOrDefault(o => o.Contains("WindowsTitle"));

        if (old != null)
            Application.Current.Resources.MergedDictionaries.Remove(old);

        Application.Current.Resources.MergedDictionaries.Add(lanRd);

        Configuration configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
        configuration.AppSettings.Settings[KEY_OF_LANGUAGE].Value = language;
        configuration.Save();
        ConfigurationManager.RefreshSection("AppSettings");

        var culture = new System.Globalization.CultureInfo(language);
        System.Globalization.CultureInfo.CurrentCulture = culture;
        System.Globalization.CultureInfo.CurrentUICulture = culture;
    }
}

资源 binding 解析类

ComBox 控件通常是通过 ItemSource 进行绑定，默认情况下是无法对绑定的资源进行翻译的。
通过继承 MarkupExtension 类重写 ProvideValue 方法来实现，item 绑定资源的 Key 的解析。

/// <summary>
/// markup extension to allow binding to resourceKey in general case
/// </summary>
public class ResourceBinding : MarkupExtension
{
    #region properties

    private static DependencyObject resourceBindingKey;
    public static DependencyObject ResourceBindingKey
    {
        get => resourceBindingKey;
        set => resourceBindingKey = value;
    }

    // Using a DependencyProperty as the backing store for ResourceBindingKeyHelper.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty ResourceBindingKeyHelperProperty =
        DependencyProperty.RegisterAttached(nameof(ResourceBindingKey),
            typeof(object),
            typeof(ResourceBinding),
            new PropertyMetadata(null, ResourceKeyChanged));

    static void ResourceKeyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (!(d is FrameworkElement target) || !(e.NewValue is Tuple<object, DependencyProperty> newVal)) return;

        var dp = newVal.Item2;

        if (newVal.Item1 == null)
        {
            target.SetValue(dp, dp.GetMetadata(target).DefaultValue);
            return;
        }

        target.SetResourceReference(dp, newVal.Item1);
    }
    #endregion

    public ResourceBinding() { }

    public ResourceBinding(string path) => Path = new PropertyPath(path);

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        if ((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget)) == null) return null;

        if (((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget))).TargetObject != null && ((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget))).TargetObject.GetType().FullName is "System.Windows.SharedDp") return this;


        if (!(((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget))).TargetObject is FrameworkElement targetObject) || !(((IProvideValueTarget)serviceProvider.GetService(typeof(IProvideValueTarget))).TargetProperty is DependencyProperty targetProperty)) return null;

        #region binding
        Binding binding = new Binding
        {
            Path = Path,
            XPath = XPath,
            Mode = Mode,
            UpdateSourceTrigger = UpdateSourceTrigger,
            Converter = Converter,
            ConverterParameter = ConverterParameter,
            ConverterCulture = ConverterCulture,
            FallbackValue = FallbackValue
        };

        if (RelativeSource != null)
            binding.RelativeSource = RelativeSource;

        if (ElementName != null)
            binding.ElementName = ElementName;

        if (Source != null)
            binding.Source = Source;
        #endregion

        var multiBinding = new MultiBinding
        {
            Converter = HelperConverter.Current,
            ConverterParameter = targetProperty
        };

        multiBinding.Bindings.Add(binding);
        multiBinding.NotifyOnSourceUpdated = true;
        targetObject.SetBinding(ResourceBindingKeyHelperProperty, multiBinding);

        return null;
    }

    #region Binding Members
    /// <summary>
    /// The source path (for CLR bindings).
    /// </summary>
    public object Source { get; set; }
    /// <summary>
    /// The source path (for CLR bindings).
    /// </summary>
    public PropertyPath Path { get; set; }
    /// <summary>
    /// The XPath path (for XML bindings).
    /// </summary>
    [DefaultValue(null)]
    public string XPath { get; set; }
    /// <summary>
    /// Binding mode
    /// </summary>
    [DefaultValue(BindingMode.Default)]
    public BindingMode Mode { get; set; }
    /// <summary>
    /// Update type
    /// </summary>
    [DefaultValue(UpdateSourceTrigger.Default)]
    public UpdateSourceTrigger UpdateSourceTrigger { get; set; }
    /// <summary>
    /// The Converter to apply
    /// </summary>
    [DefaultValue(null)]
    public IValueConverter Converter { get; set; }
    /// <summary>
    /// The parameter to pass to converter.
    /// </summary>
    /// <value></value>
    [DefaultValue(null)]
    public object ConverterParameter { get; set; }
    /// <summary>
    /// Culture in which to evaluate the converter
    /// </summary>
    [DefaultValue(null)]
    [TypeConverter(typeof(System.Windows.CultureInfoIetfLanguageTagConverter))]
    public CultureInfo ConverterCulture { get; set; }
    /// <summary>
    /// Description of the object to use as the source, relative to the target element.
    /// </summary>
    [DefaultValue(null)]
    public RelativeSource RelativeSource { get; set; }
    /// <summary>
    /// Name of the element to use as the source
    /// </summary>
    [DefaultValue(null)]
    public string ElementName { get; set; }
    #endregion

    #region BindingBase Members
    /// <summary>
    /// Value to use when source cannot provide a value
    /// </summary>
    /// <remarks>
    /// Initialized to DependencyProperty.UnsetValue; if FallbackValue is not set, BindingExpression
    /// will return target property's default when Binding cannot get a real value.
    /// </remarks>
    public object FallbackValue { get; set; }
    #endregion

    #region Nested types
    private class HelperConverter : IMultiValueConverter
    {
        public static readonly HelperConverter Current = new HelperConverter();

        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
        {
            return Tuple.Create(values[0], (DependencyProperty)parameter);
        }

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