The cross-thread usage of "HttpContext.Current" property and related things
- by smwikipedia
I read from < Essential ASP.NET with Examples in C# the following statement:
Another useful property to know about is the static Current property
of the HttpContext class. This property always points to the current
instance of the HttpContext class for the request being serviced. This
can be convenient if you are writing helper classes that will be used
from pages or other pipeline classes and may need to access the
context for whatever reason. By using the static Current property to
retrieve the context, you can avoid passing a reference to it to
helper classes. For example, the class shown in Listing 4-1 uses the
Current property of the context to access the QueryString and print
something to the current response buffer. Note that for this static
property to be correctly initialized, the caller must be executing on
the original request thread, so if you have spawned additional threads
to perform work during a request, you must take care to provide access
to the context class yourself.
I am wondering about the root cause of the bold part, and one thing leads to another, here is my thoughts:
We know that a process can have multiple threads. Each of these threads have their own stacks, respectively. These threads also have access to a shared memory area, the heap.
The stack then, as I understand it, is kind of where all the context for that thread is stored. For a thread to access something in the heap it must use a pointer, and the pointer is stored on its stack.
So when we make some cross-thread calls, we must make sure that all the necessary context info is passed from the caller thread's stack to the callee thread's stack.
But I am not quite sure if I made any mistake.
Any comments will be deeply appreciated.
Thanks.
ADD
Here the stack is limited to user stack.
