Threading in C# , value types and reference types clarification?
Neither thread simply "runs DoWork
"; they run DoWork
on a particular object. If the two threads are created targeting different instances, then mp
and g
will be completely separate fields. If the two threads are created targeting the same instance, then mp
and g
will be shared but it is not guaranteed that the threads will see changes made by the other thread unless you use synchronization or volatile
access.
For example:
var obj = new SomeObject();Thread thread1 = new Thread(obj.DoWork);Thread thread2 = new Thread(obj.DoWork); // clearly targeting the same instance
vs
var obj = new SomeObject();Thread thread1 = new Thread(obj.DoWork);obj = new SomeObject();Thread thread2 = new Thread(obj.DoWork); // targeting a different instance
The local variables i
and mp2
are strictly specific to each thread.
Additional note: even if they are separate fields/locals, if some of the code in the ...
later reassigns mp
or mp2
to refer to the same object, then they will be squabbling over the same object; the same synchronization / volatile
rules will apply.
The variables g
and mp
are 'global' to the containing class, so these will be the same objects seen by both threads. i
is a local variable that is declared in the DoWork
event; subsequently this will only be 'visible' to the background/alternative thread.
They don't 'see' the same, so the static
keyword in this case has no relevence.
I hope this helps.