C#: Adding context to Parallel.ForEach() in ASP.NET

Question

I have a static class with a static get property, and in this property, I do this:

// property body
{
    // HttpContext.Current is NOT null
    ...

    Parallel.ForEach(files, file =>
    {
        // HttpContext.Current is null
        var promo = new Promotion();
        ...
    });
    ...

    // HttpContext.Current is NOT null
}

This static class doesn't undergone type initialization until a view uses this property.

The problem is that Promotion's static constructor, which is initialized the first time a new Promotion() is created within the Parallel.ForEach(), uses HttpContext.Current. When promo is instantiated within the scope of this Parallel.ForEach(), HttpContext.Current is null, and new Promotion() therefore causes an exception.

HttpContext.Current is not null within the static get property because it's not called until the view uses it (and there is therefore a HttpContext.Current).

If Promotion used HttpContext.Current in its instances instead of its static members, I could probably just pass HttpContext.Current into the new Promotion() constructor:

 var context = HttpContext.Current;
 Parallel.ForEach(files, file =>
 {
     var promo = new Promotion(context);
 });

But since static members of Promotion need HttpContext.Current, I can't. I could probably redesign the Promotion class to change the static members that need it to be instance members, but they are static for a reason--there would be a large performance penalty if all the members that were static had to be defined instead on each instance each time a new Promotion was instantiated.

What are the possible workarounds for this? I didn't realize HttpContext.Current would be null within the scope of Parallel.ForEach().

Answer 1

Just pass any context you have from outside the Parallel.ForEach call down into any functions you call inside that rely on said context.

var context = HttpContext.Current;
Parallel.ForEach(items, item =>
    {
        DoSomething(item, context);
    }
);



private static void DoSomething(item, context = null) {
    if (context == null) context = HttpContext.Current;

    ...
}

I like to have fallback to null so I don't have to worry about passing around the context all the time. I only make sure to remember that my functions need context when calling from another thread, and then I slap that baby right in there.