ASP.NET核心:以编程方式为本地化视图设置资源文件

首先,我不太确定你的要求是否必要。但通过深入研究源代码,我发现这是可能的,并在这里提出了一个解决方案。

其实 IViewLocalizer IHtmlLocalizerFactory 登记为单身人士。这取决于 IStringLocalizerFactory ResourceManager ResourceManagerStringLocalizerFactory . LocalizationOptions 要获得配置的 ResourcesPath 用于创建的实例 IStringLocalizer HtmlLocalizer 最后裹上 ViewLocalizer . 这里的要点是,结果由缓存键缓存,具体取决于视图/页面路径&程序集的名称(资源嵌入其中)。所以在第一次创建 视图定位器 (通过DI提供),它将被缓存,您没有机会更改配置的 资源量 或者拦截来改变它。

这意味着我们需要一个定制 ResourceManagerStringLocalizerFactory 覆盖 Create 方法(实际上它不是虚拟的,但我们可以重新实现它)。我们需要在缓存键中包含另外一个因素(运行时资源路径),以便缓存能够正常工作。还有一个虚拟方法 ResourceManagerStringLocalizerFactory 可以重写以提供运行时资源路径的: GetResourceLocationAttribute . 最小化自定义的实现代码 ResourceManagerStringLocalizerFactory

这是核心原则。然而,当涉及到完整解决方案的实现时,它并没有那么简单。以下是完整的代码:

/// <summary>
/// A ViewLocalizer that can be aware of the request feature IActiveViewLocalizerFeature to use instead of 
/// basing on the default implementation of ViewLocalizer
/// </summary>
public class ActiveLocalizerAwareViewLocalizer : ViewLocalizer
{
    readonly IHttpContextAccessor _httpContextAccessor;
    public ActiveLocalizerAwareViewLocalizer(IHtmlLocalizerFactory localizerFactory, IHostingEnvironment hostingEnvironment,
        IHttpContextAccessor httpContextAccessor) : base(localizerFactory, hostingEnvironment)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    public override LocalizedHtmlString this[string key, params object[] arguments]
    {
        get
        {
            var localizer = _getActiveLocalizer();
            return localizer == null ? base[key, arguments] : localizer[key, arguments];
        }
    }

    public override LocalizedHtmlString this[string key]
    {
        get
        {
            var localizer = _getActiveLocalizer();
            return localizer == null ? base[key] : localizer[key];
        }
    }
    IHtmlLocalizer _getActiveLocalizer()
    {
        return _httpContextAccessor.HttpContext.Features.Get<IActiveViewLocalizerFeature>()?.ViewLocalizer;
    }
}

public static class HtmlLocalizerFactoryWithRuntimeResourcesPathExtensions
{
    public static T WithResourcesPath<T>(this T factory, string resourcesPath) where T : IHtmlLocalizerFactory
    {
        if (factory is IRuntimeResourcesPath overridableFactory)
        {
            overridableFactory.SetRuntimeResourcesPath(resourcesPath);
        }
        return factory;
    }
}

public interface IActiveViewLocalizerFeature
{
    IHtmlLocalizer ViewLocalizer { get; }
}

public class ActiveViewLocalizerFeature : IActiveViewLocalizerFeature
{
    public ActiveViewLocalizerFeature(IHtmlLocalizer viewLocalizer)
    {
        ViewLocalizer = viewLocalizer;
    }
    public IHtmlLocalizer ViewLocalizer { get; }
}

public interface IRuntimeResourcesPath
{
    string ResourcesPath { get; }
    void SetRuntimeResourcesPath(string resourcesPath);
}

public class RuntimeResourcesPathHtmlLocalizerFactory : HtmlLocalizerFactory, IRuntimeResourcesPath
{
    readonly IStringLocalizerFactory _stringLocalizerFactory;
    public RuntimeResourcesPathHtmlLocalizerFactory(IStringLocalizerFactory localizerFactory) : base(localizerFactory)
    {
        _stringLocalizerFactory = localizerFactory;
    }
    //NOTE: the factory is registered as a singleton, so we need this to manage different resource paths used on different tasks
    readonly AsyncLocal<string> _asyncResourcePath = new AsyncLocal<string>();
    public string ResourcesPath => _asyncResourcePath.Value;

    void IRuntimeResourcesPath.SetRuntimeResourcesPath(string resourcesPath)
    {
        _asyncResourcePath.Value = resourcesPath;
    }
    public override IHtmlLocalizer Create(string baseName, string location)
    {
        if (_stringLocalizerFactory is IRuntimeResourcesPath overridableFactory)
        {
            overridableFactory.SetRuntimeResourcesPath(ResourcesPath);
        }
        return base.Create(baseName, location);
    }
}

public static class RuntimeResourcesPathHtmlLocalizerFactoryExtensions
{
    /// <summary>
    /// Creates an IHtmlLocalizer with a runtime resources path (instead of using the configured ResourcesPath)
    /// </summary>
    public static IHtmlLocalizer CreateWithResourcesPath(this IHtmlLocalizerFactory factory, string resourcesPath, string baseName, string location = null)
    {
        location = location ?? Assembly.GetEntryAssembly().GetName().Name;
        var result = factory.WithResourcesPath(resourcesPath).Create(baseName, location);
        factory.WithResourcesPath(null);
        return result;
    }
}

public static class RuntimeResourcesPathLocalizationExtensions
{
    static IHtmlLocalizer _useLocalizer(ActionContext actionContext, string resourcesPath, string viewPath)
    {
        var factory = actionContext.HttpContext.RequestServices.GetRequiredService<IHtmlLocalizerFactory>();

        viewPath = viewPath.Substring(0, viewPath.Length - Path.GetExtension(viewPath).Length).TrimStart('/', '\\')
                   .Replace("/", ".").Replace("\\", ".");

        var location = Assembly.GetEntryAssembly().GetName().Name;

        var localizer = factory.CreateWithResourcesPath(resourcesPath, viewPath, location);
        actionContext.HttpContext.Features.Set<IActiveViewLocalizerFeature>(new ActiveViewLocalizerFeature(localizer));
        return localizer;
    }
    /// <summary>
    /// Can be used inside Controller
    /// </summary>
    public static IHtmlLocalizer UseLocalizer(this ActionContext actionContext, string resourcesPath, string viewOrPageName = null)
    {
        //find the view before getting the path
        var razorViewEngine = actionContext.HttpContext.RequestServices.GetRequiredService<IRazorViewEngine>();
        if (actionContext is ControllerContext cc)
        {
            viewOrPageName = viewOrPageName ?? cc.ActionDescriptor.ActionName;
            var viewResult = razorViewEngine.FindView(actionContext, viewOrPageName, false);
            return _useLocalizer(actionContext, resourcesPath, viewResult.View.Path);
        }
        var pageResult = razorViewEngine.FindPage(actionContext, viewOrPageName);
        //NOTE: here we have pageResult.Page is an IRazorPage but we don't use that to call UseLocalizer
        //because that IRazorPage instance has very less info (lacking ViewContext, PageContext ...)
        //The only precious info we have here is the Page.Path
        return _useLocalizer(actionContext, resourcesPath, pageResult.Page.Path);
    }
    /// <summary>
    /// Can be used inside Razor View or Razor Page
    /// </summary>
    public static IHtmlLocalizer UseLocalizer(this IRazorPage razorPage, string resourcesPath)
    {
        var path = razorPage.ViewContext.ExecutingFilePath;
        if (string.IsNullOrEmpty(path))
        {
            path = razorPage.ViewContext.View.Path;
        }
        if (path == null) return null;
        return _useLocalizer(razorPage.ViewContext, resourcesPath, path);
    }
    /// <summary>
    /// Can be used inside PageModel
    /// </summary>
    public static IHtmlLocalizer UseLocalizer(this PageModel pageModel, string resourcesPath)
    {
        return pageModel.PageContext.UseLocalizer(resourcesPath, pageModel.RouteData.Values["page"]?.ToString()?.TrimStart('/'));
    }
}

ResourceManagerStringLocalizerFactory

public class RuntimeResourcesPathResourceManagerStringLocalizerFactory 
    : ResourceManagerStringLocalizerFactory, IRuntimeResourcesPath, IStringLocalizerFactory
{
    readonly AsyncLocal<string> _asyncResourcePath = new AsyncLocal<string>();
    public string ResourcesPath => _asyncResourcePath.Value;
    private readonly ConcurrentDictionary<string, ResourceManagerStringLocalizer> _localizerCache =
        new ConcurrentDictionary<string, ResourceManagerStringLocalizer>();

    public RuntimeResourcesPathResourceManagerStringLocalizerFactory(IOptions<LocalizationOptions> localizationOptions, ILoggerFactory loggerFactory) : base(localizationOptions, loggerFactory)
    {
    }
    protected override ResourceLocationAttribute GetResourceLocationAttribute(Assembly assembly)
    {
        //we is where we override the configured ResourcesPath and use the runtime ResourcesPath.
        return ResourcesPath == null ? base.GetResourceLocationAttribute(assembly) : new ResourceLocationAttribute(ResourcesPath);
    }        

    public void SetRuntimeResourcesPath(string resourcesPath)
    {
        _asyncResourcePath.Value = resourcesPath;
    }
    /// <summary>
    /// Almost cloned from the source code of ResourceManagerStringLocalizerFactory
    /// We need to re-implement this because the framework code caches the result of Create using a cache key depending on only baseName & location.
    /// But here we introduce one more parameter of (runtime) ResourcesPath, so we need to include that in the cache key as well for 
    /// it to work properly (otherwise each time changing the runtime ResourcesPath, the same cached result will be returned, which is wrong).
    /// </summary>        
    IStringLocalizer IStringLocalizerFactory.Create(string baseName, string location)
    {
        if (baseName == null)
        {
            throw new ArgumentNullException(nameof(baseName));
        }

        if (location == null)
        {
            throw new ArgumentNullException(nameof(location));
        }

        return _localizerCache.GetOrAdd($"B={baseName},L={location},R={ResourcesPath}", _ =>
        {
            var assemblyName = new AssemblyName(location);
            var assembly = Assembly.Load(assemblyName);
            baseName = GetResourcePrefix(baseName, location);

            return CreateResourceManagerStringLocalizer(assembly, baseName);
        });
    }
}

public static class RuntimeResourcesPathLocalizationServiceCollectionExtensions
{
    public static IServiceCollection AddRuntimeResourcesPathForLocalization(this IServiceCollection services)
    {
        services.AddSingleton<IStringLocalizerFactory, RuntimeResourcesPathResourceManagerStringLocalizerFactory>();
        services.AddSingleton<IHtmlLocalizerFactory, RuntimeResourcesPathHtmlLocalizerFactory>();
        return services.AddSingleton<IViewLocalizer, ActiveLocalizerAwareViewLocalizer>();
    }
}

我们实现了一个定制 IVEWLLOCALizer 这样它就可以无缝地用于您的代码中。它的工作只是检查是否有任何活动的 IHtmlLocalizer HttpContext (作为一个称为 IActiveViewLocalizerFeature . 每个不同的运行时资源路径将创建不同的 将作为活动定位器共享。通常在一个请求范围内(以及在视图上下文中),我们通常只需要使用一个运行时资源路径(在呈现视图之前的最开始处指定)。

要注册自定义服务,请执行以下操作:

services.AddRuntimeResourcesPathForLocalization();

要将定位器与运行时资源路径一起使用,请执行以下操作:

public async Task<IActionResult> ShowSomething([FromQuery] bool useDifferentResource)
{
  if (useDifferentResource)
  {
     this.UseLocalizer("resources path of your choice");
  }
    
  return View("MyView");
}

笔记 字体 UseLocalizer 在控制器或页面模型的作用域内,由于查找视图/页面的额外逻辑(使用 IRazorViewEngine 使用定位器 到 RazorPage 或 View