http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660Does the program become self-aware and try to take over the world? http://ayende.com/4210/a-thread-static-instance#comment22http://ayende.com/4210/a-thread-static-instance#comment22Sun, 04 Oct 2009 23:53:32 GMTIs the output "Hello World"? http://ayende.com/4210/a-thread-static-instance#comment21http://ayende.com/4210/a-thread-static-instance#comment21Thu, 24 Sep 2009 12:17:52 GMT It would have been *very* weird if a (thread) static variable could be set via : new Strange {Value = 1}; As that would seems static at all. So most obviously output *must* be 1,2, 1,2 Would have been a whole different when the static keyword was not commented as then we could only set it via: Strange.Value = 1; And *if* that was marked with [ThreadStatic] I would expect thread static behavior. Just as others imply. http://ayende.com/4210/a-thread-static-instance#comment20http://ayende.com/4210/a-thread-static-instance#comment20Thu, 24 Sep 2009 12:09:33 GMT@Chris Kemp It shouldn't throw a compiler error unless it is mentioned in the language spec; it *isn't* mentioned (it is an implementation feature) - and the only other escape-hatch is §17.5 which only applies to attributes under the System.Runtime.InteropServices namespace (ThreadStaticAttribute is in the System namespace). http://ayende.com/4210/a-thread-static-instance#comment19http://ayende.com/4210/a-thread-static-instance#comment19Thu, 24 Sep 2009 07:55:17 GMTI'd expect it to throw a compiler error, but if it did that then you'd not be posting it on here, would you? :) http://ayende.com/4210/a-thread-static-instance#comment18http://ayende.com/4210/a-thread-static-instance#comment18Thu, 24 Sep 2009 07:38:17 GMTIt behaves like I expected (1,2,1,2) - I guess the main problem is that there simply isn't a way of specifying that an attribute only applies to *static* (no AttributeTargets enum). http://ayende.com/4210/a-thread-static-instance#comment17http://ayende.com/4210/a-thread-static-instance#comment17Thu, 24 Sep 2009 06:03:23 GMTRan the code and got the expected 1 2 1 2 http://ayende.com/4210/a-thread-static-instance#comment16http://ayende.com/4210/a-thread-static-instance#comment16Thu, 24 Sep 2009 03:22:29 GMTOops just realized that the variable is not static...hmm, I don't know brain, what will happen here? http://ayende.com/4210/a-thread-static-instance#comment15http://ayende.com/4210/a-thread-static-instance#comment15Thu, 24 Sep 2009 02:26:05 GMTYou'll get 2 2 0 0 Becase it's thread static, the variable is shared among all instances for a given thread. The writelines on the main thread will use the last value assigned (2). The writelines in the threadpool thread are never initialized and have 0. http://ayende.com/4210/a-thread-static-instance#comment14http://ayende.com/4210/a-thread-static-instance#comment14Thu, 24 Sep 2009 02:21:18 GMTI'd expect either an error as ThreadStatic is only intended for static members, or it to be ignored, resulting in 1-2-1-2. However, if ThreadStatic did work on non-static fields (a bug I'd figure) then I'd expect 1-2-2-2. http://ayende.com/4210/a-thread-static-instance#comment13http://ayende.com/4210/a-thread-static-instance#comment13Thu, 24 Sep 2009 02:07:53 GMTI hope it prints 1,2,1,2 I would consider everything else a bug (if it is not documented somewhere).... The attribute should be ignored if not applied to a static field as others explained already, but as you are blogging about it, I guess this is not the actual result of the code, is it? http://ayende.com/4210/a-thread-static-instance#comment12http://ayende.com/4210/a-thread-static-instance#comment12Thu, 24 Sep 2009 01:06:53 GMTObviously 1, 2, 1, 2. Like Tommi said, ThreadStatic only affects static fields. If you add the static... Well the code wouldn't compile because you're calling a static field on an instance (s1.Value) but if you fix that you'd get 2, 2, 0, 0. http://ayende.com/4210/a-thread-static-instance#comment11http://ayende.com/4210/a-thread-static-instance#comment11Wed, 23 Sep 2009 22:06:03 GMTThe ThreadStaticAttribute only affects static members. So, this would do the same thing it would do if you didn't have the attribute at all: 1 2 1 2 http://ayende.com/4210/a-thread-static-instance#comment10http://ayende.com/4210/a-thread-static-instance#comment10Wed, 23 Sep 2009 22:05:15 GMTIn the example it will only print 1 2 Put a sleep or a ReadLine() and it will 1 2 1 2 Because instance variables are not thread static, so you're passing the same references to the threadpool. http://ayende.com/4210/a-thread-static-instance#comment9http://ayende.com/4210/a-thread-static-instance#comment9Wed, 23 Sep 2009 22:01:05 GMT2 2 0 0? http://ayende.com/4210/a-thread-static-instance#comment8http://ayende.com/4210/a-thread-static-instance#comment8Wed, 23 Sep 2009 21:46:30 GMT1-2-2-2 !??!?! http://ayende.com/4210/a-thread-static-instance#comment7http://ayende.com/4210/a-thread-static-instance#comment7Wed, 23 Sep 2009 21:32:24 GMTThe attribute will not make an instance field (thread) static, at least I hope it won't. http://ayende.com/4210/a-thread-static-instance#comment6http://ayende.com/4210/a-thread-static-instance#comment6Wed, 23 Sep 2009 21:22:56 GMTIt's obvious - with commented: /* static */ it will be 1212 - ThreadStatic attribute works only with static fields. http://ayende.com/4210/a-thread-static-instance#comment5http://ayende.com/4210/a-thread-static-instance#comment5Wed, 23 Sep 2009 20:44:33 GMTYou wouldn't ask it if the answer would not be 1-2-1-2 I guess, but I don't have any idea why. http://ayende.com/4210/a-thread-static-instance#comment4http://ayende.com/4210/a-thread-static-instance#comment4Wed, 23 Sep 2009 20:38:55 GMTit will input : 1 2 but if you want it to input them twice you need to keep the appliction running so if you add Console.Read(); at the end it will print 1 2 1 2 http://ayende.com/4210/a-thread-static-instance#comment3http://ayende.com/4210/a-thread-static-instance#comment3Wed, 23 Sep 2009 20:35:33 GMTand '1' and '2' before that... http://ayende.com/4210/a-thread-static-instance#comment2http://ayende.com/4210/a-thread-static-instance#comment2Wed, 23 Sep 2009 20:21:02 GMTI'd expect it to print '0' twice http://ayende.com/4210/a-thread-static-instance#comment1http://ayende.com/4210/a-thread-static-instance#comment1Wed, 23 Sep 2009 20:19:29 GMT