How to correctly inherit thread culture in a parallel block?

Question

I'm using automatic globalization on an ASP MVC website. It works fine until it reached a parallel block:

public ActionResult Index() 
{
     // Thread.CurrentThread.CurrentCulture is automatically set to "fr-FR"
     // according to the requested "Accept-Language" header

     Parallel.Foreach(ids, id => {
        // Not every thread in this block has the correct culture. 
        // Some of them still have the default culture "en-GB"
     }) ; 

     return View()
}

What is the best way to make the parallel block inherit the culture? apart from this solution:

public ActionResult Index() 
{
     var currentCulture = Thread.CurrentThread.CurrentCulture  ;

     Parallel.Foreach(ids, id => {
         // I don't know if it's threadsafe or not. 
         Thread.CurrentThread.CurrentCulture = currentCulture ; 

     }) ; 

     return View()
}

Jester

Probably, one of them has the culture of the request because of task inlining. The other ones should follow thread pool behavior whatever that is (I never found out). – Biflagellate

Answer 1

You can create your own Parallel.ForEach handling thread culture :

public static class ParallelInheritCulture
{
    public static ParallelLoopResult ForEach<T>(IEnumerable<T> source, Action<T> body)
    {
        var parentThreadCulture = Thread.CurrentThread.CurrentCulture; 
        var parentThreadUICulture = Thread.CurrentThread.CurrentUICulture; 

        return Parallel.ForEach(source, e =>
        {
            var currentCulture = Thread.CurrentThread.CurrentCulture; 
            var currentUICulture = Thread.CurrentThread.CurrentUICulture; 

            try
            {
                Thread.CurrentThread.CurrentCulture = parentThreadCulture;
                Thread.CurrentThread.CurrentUICulture = parentThreadUICulture;

                body(e); 
            }
            finally
            {
                Thread.CurrentThread.CurrentCulture = currentCulture;
                Thread.CurrentThread.CurrentUICulture = currentUICulture;
            }
        }); 
    }
}

Then:

 ParallelInheritCulture.Foreach(ids, id => {
    // Whatever

 }) ; 

Ostium

What's the need to revert the culture inside parallel.? – Brook