How do I access HttpContext.Current in Task.Factory.StartNew?

问题

I want to access HttpContext.Current in my asp.net application within

Task.Factory.Start(() =>{
    //HttpContext.Current is null here
});

How can I fix this error?

回答1:

Task.Factory.Start will fire up a new Thread and because the HttpContext.Context is local to a thread it won't be automaticly copied to the new Thread, so you need to pass it by hand:

var task = Task.Factory.StartNew(
    state =>
        {
            var context = (HttpContext) state;
            //use context
        },
    HttpContext.Current);

回答2:

You could use a closure to have it available on the newly created thread:

var currentContext = HttpContext.Current;

Task.Factory.Start(() => {
    // currentContext is not null here
});

But keep in mind that a task can outlive the lifetime of the HTTP request and could lead to funny results when accessing the HTTPContext after the request has completed.

回答3:

As David pointed out, HttpContext.Current will not work all the time. In my case, about 1 of 20 time, CurrentContext will be null. End up with below.

string UserName = Context.User.Identity.Name;

System.Threading.Tasks.Task.Factory.StartNew(() =>
{
    UserName ...
}

来源：https://stackoverflow.com/questions/10662456/how-do-i-access-httpcontext-current-in-task-factory-startnew