ASP.NET Core MVC 路由问题答案

【问题标题】：ASP.NET Core MVC Route issueASP.NET Core MVC 路由问题
【发布时间】：2017-12-28 01:30:50
【问题描述】：

我正在尝试设置一个 ASP.NET Core MVC 站点以支持多个国家/地区的多语言，例如：

www.test.com/au/en（澳大利亚，英语）
www.test.com/au/de（澳大利亚、德语）

为当前用户设置文化，我找到了这段代码

public static class GetRoutesMiddlewareExtensions
{
    public static IApplicationBuilder UseGetRoutesMiddleware(this IApplicationBuilder app, Action<IRouteBuilder> configureRoutes)
    {
        if (app == null)
        {
            throw new ArgumentNullException(nameof(app));
        }

        var routes = new RouteBuilder(app)
        {
            DefaultHandler = app.ApplicationServices.GetRequiredService<MvcRouteHandler>(),
        };
        configureRoutes(routes);
        routes.Routes.Insert(0, AttributeRouting.CreateAttributeMegaRoute(app.ApplicationServices));
        var router = routes.Build();

        return app.UseMiddleware<GetRoutesMiddleware>(router);
    }
}

public class GetRoutesMiddleware
{
    private readonly RequestDelegate next;
    private readonly IRouter _router;

    public GetRoutesMiddleware(RequestDelegate next, IRouter router)
    {
        this.next = next;
        _router = router;
    }

    public async Task Invoke(HttpContext httpContext)
    {
        var context = new RouteContext(httpContext);
        context.RouteData.Routers.Add(_router);

        await _router.RouteAsync(context);

        if (context.Handler != null)
        {
            httpContext.Features[typeof(IRoutingFeature)] = new RoutingFeature()
            {
                RouteData = context.RouteData,
            };
        }

        // proceed to next...
        await next(httpContext);
    }
}

我创建了一个如下所示的 RequestCultureProvider：

public class RequestCultureProvider : IRequestCultureProvider
{
    public Task<ProviderCultureResult> DetermineProviderCultureResult(HttpContext httpContext)
    {
        if (httpContext.GetRouteValue("language") == null)
        {
            return Task.FromResult(new ProviderCultureResult("en", "en"));
        }
        var langauge = httpContext.GetRouteValue("language").ToString().ToLower();
        return Task.FromResult(new ProviderCultureResult(langauge, langauge));
    }
}

设置路线我有这个方法：

private readonly Action<IRouteBuilder> GetRoutes =
    routes =>
    {
        routes.MapRoute(name: "Default",
                        template: "{area}/{language}/{controller}/{action}",
                        defaults: new { area = "au", language = "en", controller = "home", action = "Index" },
                        constraints: new { area = new RequiredRouteConstraint(), language = new RegexRouteConstraint("^(en|de)$")  });
    };

然后在 Startup.cs 中，在 Configure 中，然后我有

// setup routes
app.UseGetRoutesMiddleware(GetRoutes);
// add localization
var supportedCultures = new List<CultureInfo>() {
                new CultureInfo("en"),
                new CultureInfo("de"),
            };

var requestLocalizationOptions = new RequestLocalizationOptions
{
    DefaultRequestCulture = new RequestCulture(supportedCultures.First()),
    SupportedCultures = supportedCultures,
    SupportedUICultures = supportedCultures,
};
requestLocalizationOptions.RequestCultureProviders.Clear();
requestLocalizationOptions.RequestCultureProviders.Add(
    new RequestCultureProvider()
);
app.UseRequestLocalization(requestLocalizationOptions);

我不确定它是否相关，但为了以更有条理的方式布局我的视图，我设置了一个如下所示的 CultureViewExpander：

public class CultureViewExpander : IViewLocationExpander
{
    public IEnumerable<string> ExpandViewLocations(ViewLocationExpanderContext context, IEnumerable<string> viewLocations)
    {
        return viewLocations.Select(s => s.Replace("%1", CultureInfo.CurrentUICulture.TwoLetterISOLanguageName));
    }

    public void PopulateValues(ViewLocationExpanderContext context)
    {
        context.Values.Add("Language", CultureInfo.CurrentUICulture.TwoLetterISOLanguageName);
    }
}

它是在 Startup.cs 中的 ConfigureServices 中实现的

services.Configure<RazorViewEngineOptions>(o =>
{
    o.ViewLocationExpanders.Add(new CultureViewExpander());

    // {0} for the action
    // {1} for the controller
    // {2} for the area
    // %1 for language
    o.ViewLocationFormats.Clear();
    o.ViewLocationFormats.Add("/Views/Shared/{0}" + RazorViewEngine.ViewExtension);

    o.AreaViewLocationFormats.Clear();
    o.AreaViewLocationFormats.Insert(0, "/Areas/{2}/Views/{1}/%1/{0}" + RazorViewEngine.ViewExtension);
});

支持的语言工作正常，但是当我导航到 www.test.com/au/fr 时，我只是得到一个空白屏幕，但我需要它来返回 404。我怎样才能让它返回 404路由值无效？

【问题讨论】：

您能否展示将language 映射到UI 文化的代码部分？

标签： asp.net-mvc asp.net-core asp.net-core-mvc asp.net-core-2.0

【解决方案1】：

ASP.NET Core 对于不匹配的 URL 正确返回 404 错误，例如 www.test.com/fr。如何处理这种响应取决于浏览器。如您所述，Firefox 仅显示空白页面。 IE、Chrome 和 Opera 显示带有错误描述的页面，例如：

当应返回错误代码时，您可以自定义 ASP.NET Core 行为。您可以通过将UseStatusCodePages 添加到应用程序配置来使用简单的短信：

app.UseStatusCodePages("text/plain", "Status code page, status code: {0}");

如果请求失败，您还可以将用户重定向到自定义错误页面：

app.UseStatusCodePagesWithRedirects("/error/{0}");

确保路径 /error/404 已正确解析，否则您将无限重定向到此页面。

查看这篇文章了解更多详情：Error Handling in ASP.NET Core

【讨论】：