c# - ASP.NET CurrentUICulture 在任务和 WebAPI 延迟结果中的行为不同

Question

我正在处理一个 ASP.NET Web API 项目，在该项目中我遇到了一个问题，其中子项 Task异步运行的 s 不继承父线程的当前文化；即，即使在设置了 Thread.CurrentThread.CurrentUICulture 之后在 Controller 构造函数中，任何 Task created in the action 默认情况下具有不变文化，除非我单独设置它。这似乎已在框架 > 4.0 中修复，并且在从 3.5.2 升级目标框架后工作正常至 4.6.2 as mentioned here .

Starting with apps that target the .NET Framework 4.6, the calling thread's culture is inherited by each task, even if the task runs asynchronously on a thread pool thread.

现在任务中的文化继承按预期工作，我面临另一个奇怪的问题，该问题在 4.5.2 中不存在。如果 WebApi 操作结果的类型为 IEnumerable ，则结果将包含默认区域性。也许使用示例代码片段可以更好地解释这个问题:

public SampleController()
{
    System.Threading.Thread.CurrentThread.CurrentUICulture =
        new System.Globalization.CultureInfo("ar-AE");
}

[Route]
public IHttpActionResult Get()
{
    IEnumerable<Employee> employeesDeferred = BuildEmployees(true);
    return Ok(employeesDeferred);
}

private IEnumerable<Employee> BuildEmployees(bool isDeferred)
{
    var employees = Enumerable.Range(0, 2)
        .Select(count => new Employee
        {
            Id = count++,
            Culture = Thread.CurrentThread.CurrentUICulture.Name
        });

    if (isDeferred) { return employees; }

    return employees.ToList();
}

请注意，我在构造函数中将 UI 文化设置为“ar-AE”。 PFB结果:

• 框架 4.5.2 - Culture的所有员工都将达到预期的 AR-AE
• 框架 4.6.2 - Culture的所有员工将是 en-US(默认)
• 框架 4.6.2 通过执行 .ToList()在结果中(在上面的代码中调用 BuildEmployees(false) 而不是 BuildEmployees(true)) - Culture的所有员工都将达到预期的 AR-AE

我确实进行了一些研究并看到了建议设置 NoAsyncCurrentCulture 的答案开关，例如，通过在应用程序设置中添加开关 <add key="appContext.SetSwitch:Switch.System.Globalization.NoAsyncCurrentCulture" value="true" /> - 但这将有点回滚到我们在 <4.0 中的行为，并将导致第一段中提到的任务中的文化继承问题。

我错过了什么？

更新:已验证上下文文化未在 Web API 中发生 (JSON/XML) 序列化的线程中继承。

Answer 1

如问题中所述，调用线程的 UICulture 未流向执行序列化的线程。为了验证这一点，我创建了一个自定义 JsonConverter (NewtonSoft) 并将其作为默认转换器添加到我的 WebAPI 中，并在 WriteJson 方法中检查了 UICulture - 正如预期的那样，我的 UICulture设置被覆盖/丢失，并且该线程具有不变的文化。

我不想玩太多重写整个 JsonConverter 因此没有继续;相反，我需要的是在操作本身的上下文中(UI Culture 已正确设置)强制序列化 API 的响应。下面的自定义过滤器也实现了同样的效果，我在其中调用了响应内容的 LoadIntoBufferAsync():

    /// <summary>
    /// BUG Description and History:
    /// We had an issue where the child Tasks/async operations were not inheriting the the current culture of the parent thread;
    /// i.e., even after setting the Thread.CurrentThread.CurrentUICulture in the controller constructor, any Task created within the action was having the invariant culture by default 
    /// unless it is set it separately. This seems to have fixed in framework > 4.0 and was working fine after upgrading the target framework from 3.5.2 to 4.6.2
    /// ref - https://learn.microsoft.com/en-us/dotnet/standard/parallel-programming/task-based-asynchronous-programming
    /// But with this fix in framework, there introduced an unnoticed? bug where in the UI culture do not flow from the calling thread's context to the NewtonSoft Json Serializer write
    /// And hence, any deferred serialization (like IEnumerable) will run under the Invariant Culture (en-US) thus ending up picking the english resource file instead of the culture set for the thread.
    /// This works fine in framework 3.5.2 or if we enable the "Switch.System.Globalization.NoAsyncCurrentCulture" switch in 4.6.2. But using the switch will diable the flow of culture in async operations and will end up having the issue
    /// we had in 3.5.2.
    /// Inorder to fix this issue, the workaround is to force the serialization happen in the action context itself where the thread UI culture is the one we have set.
    /// </summary>
    public class ForceSerializeHttpContentFilter : ActionFilterAttribute
    {
        public override void OnActionExecuted(HttpActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);
            filterContext.Response.Content.LoadIntoBufferAsync().Wait();
        }
    }

不确定这是否是正确的解决方法；等待社区的更多回应。谢谢。