MVC5并使用DropDownList，Cookie，用户配置文件设置来设置Culture / CultureUI

Question

I have partially implemented Globalization/Localization in my project. The project requires a database to be used for resource strings and I found an excellent NuGet package called WestWind.Globalization that does exactly what I needed.

This NuGet package allows you to display resource strings using several different methods. It provides an option to generate a strongly typed class that contains all of your resource strings so you can use it like:

@Html.Encode( Resources.lblResourceName )

or

object Value = this.GetLocalResourceObject("ResourceName");

or

object GlobalValue = this.GetGlobalResourceObject("Resources","ResourceKey");

and even:

dbRes.T(resourceName, resourceSet, culture)

I didn't want to specify the culture manually, so I opted for this method:

<p class="pageprompt">@AccountRequestAccount.pagePrompt</p>

For me, Westwind.Globalization is magical. It resolved a huge issue for me, but I ran into a snag that I wasn't sure how to overcome. That was, how to set the Culture/CultureUI so that the package would automatically use a specified language resource.

I created a PartialView that contains a dropdown list of languages. It is contained in the ~/Views/Shared/ folder and gets included in _Layout.cshtml. I coded the GET and POST Controller Actions which work as intended, except that I was unable to persist the Culture/CultureUI settings. I suspect that it was due to a redirect immediately following language selection (explained below)

So, I found an SO question that had an answer that seemed viable. I integrated that answer into my project. The relevant code is:

RouteConfig.cs:

 routes.MapRoute("DefaultLocalized",
 "{language}-{culture}/{controller}/{action}/{id}",
 new
 {
     controller = "Home",
     action = "Index",
     id = "",
     language = "en",
     culture = "US"
 });

~/Helpers/InternationalizationAttribute.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using System.Threading;
using System.Web;
using System.Web.Mvc;

namespace GPS_Web_App.Helpers
{
    public class InternationalizationAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            string language = 
                (string)filterContext.RouteData.Values["language"] ?? "en";

            string culture = 
                (string)filterContext.RouteData.Values["culture"] ?? "US";

            Thread.CurrentThread.CurrentCulture =
                CultureInfo.GetCultureInfo(string.Format("{0}-{1}",
                language, culture));

            Thread.CurrentThread.CurrentUICulture = 
                CultureInfo.GetCultureInfo(string.Format("{0}-{1}",
                language, culture));
        }
    }
}

In my Controllers:

[Authorize]
[Internationalization]
public class AccountController : Controller
{
    ...
}

So far so good. This works in that I am able to go to a URL of http://example.com/en-mx/Account/Login/ and see the page being localized by Westwind.Globalization and the resource strings I've created.

The problems I have with this are:

1. If the user is anonymous their language preference should be controlled by cookie (if it exists) otherwise default to en-US.

2. If the user is authenticated their language preference should be controlled by the Language field in their profile settings. (Simple Membership using ASP.NET Identity 2.0).

3. There is a language selection dropdown in a global header. The user should be able to choose their language preference from the dropdown and if they do, the setting gets written to cookie (for both anonymous and authenticated users) and if the user is authenticated their Language setting in the user profile gets updated.

4. Not the end of the world, but it would be highly preferable that the language not be included in the URL. Some might ask, well why did I install @jao's solution? Let me explain that.

All of the code was in place for the dropdown to allow a user to make a language selection. The logic for #1, #2, and #3 above were working correctly, but wouldn't take effect and trigger Westwind.Globalization's DbResourceProvider to pass the selected language resource strings.

What I discovered through debugging was that my settings were not persisting in:

System.Threading.Thread.CurrentThread.CurrentCulture = 
    System.Globalization.CultureInfo.GetCultureInfo(SelectedLanguage);
System.Threading.Thread.CurrentThread.CurrentUICulture = 
    System.Globalization.CultureInfo.GetCultureInfo(SelectedLanguage);

Through responses provided by my question here on SO I learned that those settings would not persist/take effect if a redirect was made prior to the original View rendering. Yet a redirect back to the original View seemed sensible since the language was being changed and needed to be rendered again. I think @jao's solution overcomes the redirect problem, but it forces Globalization/Localization to be specified by the URL? Somewhat of a catch-22...

I have asked @jao to review this question and provide any hints on this. I think my question is best summed up as this:

How can I use the user's cookie/profile settings to set the Culture/CultureUI once and for all so that Westwind.Globalization can read Globalization/Localization instead of relying on the Culture being passed in the URL?

Answer 1

I am posting this answer as an alternate, custom way of doing localization with ASP.NET MVC5 with asynchronous controller. Perhaps you may find some gotchas in my solution especially when it comes to routing and setting cookies.

This is sort of a short tutorial I scribbled down for my heterogeneous/custom approach. So I preferred SO over WordPress. :)

Sorry for not giving the precise and discrete answer to your problem. Hopefully it will help you in some other way, and other folks as well; who are looking to do the same sort of setup.

---

In his blog post , Nadeem Afana described a strategy of creating a separate project Resource in the solution to implement internationalization using static resource files. In the blog sequel , he detailed on extending the same project to handle resources via Databases and XML-driven approaches. For the former one, he used ADO.NET, decoupled from Entity Framework.

We needed to implement both static and dynamic resources within the MVC project, respecting the concepts of MVC conventions.

First lets add a Resources folder in project root, with the desired language variants: ~/Resources/Resources.resx (the default resource file corresponds to en-US culture), ~/Resources/Resources.fi.resx and ~/Resources/Resources.nl.resx . Mark the resources as public, so to make them available in Views.

In ~/Views/Web.config , add the resources namespace under <namespace> element: <add namespace="YourMainNamespace.Reousrces" /> . Under controllers, create a base controller class:

Here comes the cookies

namespace YourNamespace.Controllers
{
    // Don't forget to inherit other controllers with this
    public class BaseController : Controller
    {
        protected override IAsyncResult BeginExecuteCore(AsyncCallback callback, object state)
        {
            string cultureName = null;

            // Attempt to read the culture cookie from Request
            HttpCookie cultureCookie = Request.Cookies["_culture"];
            if (cultureCookie != null)
                cultureName = cultureCookie.Value;
            else
                cultureName = Request.UserLanguages != null && Request.UserLanguages.Length > 0 ?
                        Request.UserLanguages[0] :  // obtain it from HTTP header AcceptLanguages
                        null;
            // Validate culture name
            cultureName = CultureHelper.GetImplementedCulture(cultureName); // This is safe

            // Modify current thread's cultures            
            Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo(cultureName);
            Thread.CurrentThread.CurrentUICulture = Thread.CurrentThread.CurrentCulture;

            return base.BeginExecuteCore(callback, state);
        }
    }
}

Next, register a global filter to in ~/Global.asax.cs to ensure that every action should use the correct culture before executing:

Here comes the cookies again!

public class SetCultureActionFilterAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
       base.OnActionExecuting(filterContext);

        var response = filterContext.RequestContext.HttpContext.Response;
        var culture = filterContext.RouteData.Values["culture"].ToString();

        // Validate input
        culture = CultureHelper.GetImplementedCulture(culture);

        Thread.CurrentThread.CurrentUICulture = new CultureInfo(culture);

        // Save culture in a cookie
        HttpCookie cookie = filterContext.RequestContext.HttpContext.Request.Cookies["_culture"];
        if (cookie != null)
            cookie.Value = culture;   // update cookie value
        else
        {
            cookie = new HttpCookie("_culture");
            cookie.Value = culture;
            cookie.Expires = DateTime.Now.AddYears(1);
        }
        response.Cookies.Add(cookie);
    }
}

And add GlobalFilters.Filters.Add(new SetCultureActionFilterAttribute()); in MyApplication.Application_Start() method.

In ~/App_Start/RoutesConfig.cs , change the default route to:

routes.MapRoute(
    name: "Default",
    url: "{culture}/{controller}/{action}/{id}",
    defaults: new { culture = "en-US", controller = "Home", action = "Index", id = UrlParameter.Optional }
);

At this point, we would be able to use resources in view. For instance; @Resources.Headline .

Next, we will create a custom attribute called Translatable for model properties.

class TranslatableAttribute : Attribute
{ }

This is enough. But if you want to be able to specify scope, you can use this class to implement it.

Now add a model called Resource with three properties and a helper method:

public class Resource
{
    [Key, Column(Order = 0)]
    public string Culture { get; set; }

    [Key, Column(Order = 1)]
    public string Name { get; set; }

    public string Value { get; set; }

    #region Helpers
    // Probably using reflection not the best approach.
    public static string GetPropertyValue<T>(string id, string propertyName) where T : class
    {
        return GetPropertyValue<T>(id, propertyName, Thread.CurrentThread.CurrentUICulture.Name);
    }
    public static string GetPropertyValue<T>(string id, string propertyName, string culture) where T : class
    {
        Type entityType = typeof(T);
        string[] segments = propertyName.Split('.');

        if (segments.Length > 1)
        {
            entityType = Type.GetType("YourNameSpace.Models." + segments[0]);
            propertyName = segments[1];
        }

        if (entityType == null)
            return "?<invalid type>";

        var propertyInfo = entityType.GetProperty(propertyName);
        var translateableAttribute = propertyInfo.GetCustomAttributes(typeof(TranslatableAttribute), true)
                                    .FirstOrDefault();
        /*var requiredAttribute = propertyInfo.GetCustomAttributes(typeof(RequiredAttribute), true)
                                .FirstOrDefault();*/

        if (translateableAttribute == null)
            return "?<this field has no translatable attribute>";

        var dbCtx = new YourNamespaceDbContext();
        var className = entityType.Name;
        Resource resource = dbCtx.Resources.Where(r =>
                            (r.Culture == culture) &&
                            r.Name == className + id + propertyName).FirstOrDefault();

        if (resource != null)
            return resource.Value;

        //return requiredAttribute == null ? string.Empty : "?<translation not found>";
        return string.Empty;
    }
    #endregion
}

This helper method will help you retrieve the translated content. For instance in view, you can say:

var name = Resource.GetPropertyValue<Product>(item.Id.ToString(), "Name");

Note that, at any point, the data in the translatable field column is unreliable; it will always hold the last updated value. On creating the record, we will mirror all the translatable properties' values in Resource model for all supported cultures.

We are using asynchronous controllers, so for insertion, modification and deletion we will be overriding SaveChangesAsync() in our DbContext class:

public override Task<int> SaveChangesAsync()
{
    ObjectContext ctx = ((IObjectContextAdapter)this).ObjectContext;

    List<ObjectStateEntry> objectDeletedStateEntryList =
        ctx.ObjectStateManager.GetObjectStateEntries(EntityState.Deleted)
        .ToList();

    List<ObjectStateEntry> objectCreateOrModifiedStateEntryList =
        ctx.ObjectStateManager.GetObjectStateEntries(EntityState.Added
                                                    | EntityState.Modified)
        .ToList();

    // First handle the delition case,
    // before making changes to entry state
    bool changed = UpdateResources(objectDeletedStateEntryList);

    // Now save the changes
    int result = base.SaveChangesAsync().Result;

    // Finally handle the remaining cases
    changed |= UpdateResources(objectCreateOrModifiedStateEntryList);

    if (changed)
        return base.SaveChangesAsync();

    return Task.FromResult<int>(result);
}

private bool UpdateResources(List<ObjectStateEntry> objectStateEntryList)
{
    bool changed = false;

    foreach (ObjectStateEntry entry in objectStateEntryList)
    {
        var typeName = entry.EntitySet.ElementType.Name;

        if (entry.IsRelationship || typeName == "Resource")
            return false;

        var type = Type.GetType("YourNamespace.Models." + typeName);

        if (type == null) // When seeds run (db created for the first-time), sometimes types might not be create
            return false;

        if (entry.State == EntityState.Deleted)
        {
            changed |= DeleteResources(type, typeName, entry);
            continue;
        }

        foreach (var propertyInfo in type.GetProperties())
        {
            var attribute = propertyInfo.GetCustomAttributes(typeof(TranslatableAttribute), true).FirstOrDefault();

            if (attribute == null)
                continue;

            CurrentValueRecord current = entry.CurrentValues;
            object idField = current.GetValue(current.GetOrdinal("Id"));

            if (idField == null)
                continue;

            var id = idField.ToString();
            var propertyName = propertyInfo.Name;
            string newValue = current.GetValue(current.GetOrdinal(propertyName)).ToString();
            var name = typeName + id + propertyName;

            Resource existingResource = this.Resources.Find(Thread.CurrentThread.CurrentUICulture.Name, name);

            if (existingResource == null)
            {
                foreach (var culture in CultureHelper.Cultures)
                {
                    this.Resources.Add(new Resource
                    {
                        Culture = culture,
                        Name = name,
                        Value = newValue
                    });

                    changed |= true;
                }
            }
            else
            {
                existingResource.Value = newValue;
                changed |= true;
            }
        }
    }

    return changed;
}

private bool DeleteResources(Type type, string typeName, ObjectStateEntry entry)
{
    bool changed = false;
    var firstKey = entry.EntityKey.EntityKeyValues.Where(k => k.Key.Equals("Id", StringComparison.InvariantCultureIgnoreCase)).FirstOrDefault();

    if (firstKey == null)
        return false;

    var id = firstKey.Value.ToString();

    foreach (var propertyInfo in type.GetProperties())
    {
        var name = typeName + id + propertyInfo.Name;

        foreach (var culture in CultureHelper.Cultures)
        {
            Resource existingResource = this.Resources.Find(culture, name);

            if (existingResource == null)
                continue;

            this.Resources.Remove(existingResource);
            changed |= true;
        }
    }

    return changed;
}

This will take care of update and delete.