http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660This is actally in the docs: You must manually keep the delegate from being collected by the garbage collector from managed code. The garbage collector does not track reference to unmanaged code. See: [msdn.microsoft.com/.../...npointerfordelegate.aspx](http://msdn.microsoft.com/en-us/library/system.runtime.interopservices.marshal.getfunctionpointerfordelegate.aspx) http://ayende.com/4485/talk-about-nasty-bugs#comment14http://ayende.com/4485/talk-about-nasty-bugs#comment14Wed, 05 May 2010 19:39:45 GMTYes, it does. The only important thing is that it isn't rooted http://ayende.com/4485/talk-about-nasty-bugs#comment13http://ayende.com/4485/talk-about-nasty-bugs#comment13Wed, 05 May 2010 06:08:32 GMTHmmm, looks familiar ;-) Is this actually broken with a static method as well as member methods? What does reflector say the actual code looks like? http://ayende.com/4485/talk-about-nasty-bugs#comment12http://ayende.com/4485/talk-about-nasty-bugs#comment12Wed, 05 May 2010 04:04:20 GMTI suspect that if you were to run this on Mono, you WOULDN'T see this problem because it employs a conservative GC. http://ayende.com/4485/talk-about-nasty-bugs#comment11http://ayende.com/4485/talk-about-nasty-bugs#comment11Tue, 04 May 2010 23:49:05 GMT1. I've never used Marshall methods. I take it that the GetFunctionPointerForDelegate method causes the callback method to be invoked in a thread-safe manner? 2. What is the solution? Make var lpProgressRoutineIntPtr a class variable instead of a local? http://ayende.com/4485/talk-about-nasty-bugs#comment10http://ayende.com/4485/talk-about-nasty-bugs#comment10Tue, 04 May 2010 22:49:22 GMTThe reason why it only crashes if there is additional work done is that the garbage collector only runs if an allocation occurs. http://ayende.com/4485/talk-about-nasty-bugs#comment9http://ayende.com/4485/talk-about-nasty-bugs#comment9Tue, 04 May 2010 22:23:43 GMTDude! You blog so much that I wonder how you ever get work done. http://ayende.com/4485/talk-about-nasty-bugs#comment8http://ayende.com/4485/talk-about-nasty-bugs#comment8Tue, 04 May 2010 21:44:08 GMTOmariO & Michael, Wow, that was fast. Yep that is the problem. http://ayende.com/4485/talk-about-nasty-bugs#comment7http://ayende.com/4485/talk-about-nasty-bugs#comment7Tue, 04 May 2010 21:28:32 GMTYou're not using a SafeHandle? http://ayende.com/4485/talk-about-nasty-bugs#comment6http://ayende.com/4485/talk-about-nasty-bugs#comment6Tue, 04 May 2010 21:18:38 GMTCould it be that you've got SetLastError set to true, are not calling GetLastWin32Error() anywhere, and when more than one thread is running there are errors trying to be set? http://ayende.com/4485/talk-about-nasty-bugs#comment5http://ayende.com/4485/talk-about-nasty-bugs#comment5Tue, 04 May 2010 20:58:58 GMTSeconding that not keeping a reference to the delegate to prevent it from being garbage collected before CopyFileEx() is done with it could be a potential problem. I've been burned by that before myself. By the way, is there really a need to manually call Marshal.GetFunctionPointerForDelegate()? I'm pretty sure I've been able to specify an actual delegate type in a P/Invoke signature and the framework handled the conversion on its own. http://ayende.com/4485/talk-about-nasty-bugs#comment4http://ayende.com/4485/talk-about-nasty-bugs#comment4Tue, 04 May 2010 20:52:50 GMTIf you were updating a graphical progress bar, the call to update it would have to be invoked to avoid cross-threading issues. Does that also apply when writing to the console? http://ayende.com/4485/talk-about-nasty-bugs#comment3http://ayende.com/4485/talk-about-nasty-bugs#comment3Tue, 04 May 2010 20:52:25 GMTI don't know how it related to threading but one of the reasons can be that you don't keep reference to the delegate. http://ayende.com/4485/talk-about-nasty-bugs#comment2http://ayende.com/4485/talk-about-nasty-bugs#comment2Tue, 04 May 2010 20:43:44 GMTstatic & threading = trouble http://ayende.com/4485/talk-about-nasty-bugs#comment1http://ayende.com/4485/talk-about-nasty-bugs#comment1Tue, 04 May 2010 20:41:35 GMT