Develop Reference

How does running C# app inside a code profiler differ from running one outside code profiler?

I'm trying to understand how a code profiler (in this case the Drone Profiler) runs a .NET app differently from just running it directly. The reason I need to know this is because I have a very strange problem/corruption with my dev computer's .NET install which manifests itself outside of the profiler but very strangely not inside and if I can understand why I can probably fix my computer's issue.
The issue ONLY seems to affect calls to System.Net.NetworkInformation's methods (and only within .NET 3.5 to 2.0, if I build something against 4 all is well). I built a little test app which only does one thing, it calls System.Net.NetworkInformation.IsNetworkAvailable(). Outside of the profiler I get "Fatal Execution Engine Error" occurred in System.dll, and that's all the info it gives. From what I understand that error usually results from native method calls, which presumably occur when the System.dll lets some native DLL perform the IsNetworkAvailable() logic.
I tried to figure out the inside and outside the profiler difference using Process Monitor, recording events from both situations and comparing them. Both logs were the same until just a moment after iphlpapi.dll and winnsi.dll were called and just before the profiler-run code called dnsapi.dll and the non-profiler code began loading crash reporting related stuff. At that moment when it seemed to go wrong the profiler-run code created 4-6 new threads and the non-profiler (crashing) code only created 1 or 2. I don't know what that means, if anything.
Arguably unnecessary background
My Windows 7 included .NET installation (3.5 to 2.0) was working fine until my hard drive suffered some corruption and checkdisk began finding bad clusters. I imaged the drive to a new one and everything works fine except this one issue with .NET.
I need to resolve this problem reinstalling Windows or reverting to image backups.
Here are some of the things I've looked into:
I have diffed the files/directories which seemed most relevant (the .NET stuff under Windows and Program Files) pre- and post- disk trouble and seen no changes where I didn't expect any (no obvious file corruption).
I have diffed the software and system registry hives pre- and post- disk trouble and seen no changes which seemed relevant.
I have created a new user account and cleaned up any environment variables in case environment was related. No change.
I did "sfc /scannow" and it found no integrity problems.
I tried "ngen update" to regenerate pre-compiled code in case I missed something that might be damaged and nothing changed.
I removed my virus scanner to see if it was interfering, no difference.
I tried running the test code in Safe Mode, same crash issue.
I assume I need to repair my .NET installation but because Windows 7 included .NET 3.5 - 2.0 you can't just re-run a .NET installer to redo it. I do not have access to the Windows disks to try to re-install Windows over itself (the computer has a recovery partition but it is unusable); also the drive uses a whole-disk encryption solution and re-installing would be difficult.
I absolutely do not want to start from scratch here and install a fresh Windows, reinstall dozens of software packages, try and remember dozens of development-related customizations/etc.
Given all that... does anyone have any helpful advice? I need .NET 3.5 - 2.0 working as I am a developer and need to build and test against it.
Thanks!
Quinxy

The short answer is that my System.ni.dll file was damaged, I replaced it and all is well.
The long answer might help someone else by way of its approach to the solution...
My problem related to .Net being damaged in such a way that apps wouldn't run except through a profiler. I downloaded the source for the SlimTune open source profiler, built it locally, and set a break point right before the call to Process.Start(). I then compared all the parameters involved in starting the app successfully through the profiler versus manually. The only meaningful difference I found was the addition of the .NET profile parameters added to the environment variables:
cor_enable_profiling=1
cor_profiler={38A7EA35-B221-425a-AD07-D058C581611D}
I then tried setting these in my own user's environment, and voila! Now any app I ran manually would work. (I had actually tried doing the same thing a few hours earlier but I used a GUID that was included in an example and which didn't point to a real profiler and apparently .NET knew I had given it a bogus GUID and didn't run in profiling mode.)
I now went back and began reading about just how a PE file is executed by CLR hoping to figure out why it mattered that my app was run with profiling enabled. I learned a lot but nothing which seemed to apply.
I did however remember that I should recheck the chkdsk log I kept listing the files that were damaged by the drive failure. After the failure I had turned all the listed file ids into file paths/names and I had replaced all the 100+ files I could from backup but sure enough when I went back now and looked I found a note that while I had replaced 4 or 5 .NET related files successfully there was one such file I wasn't able to replace because it was "in use". That file? System.ni.dll!!! I was now able to replace this file from backup and voila my .NET install is back to normal, apps work whether profiled or not.
The frustrating thing is that when this incident first occurred I fully expected the problem to relate to a damaged file, and specifically to a file called System.dll which housed the methods that failed. And so I diffed and rediffed all files named System.dll. But I did not realize at that time that System.ni.dll was a native compiled manifestation of System.dll (or somesuch). And because I had diffed and rediffed the .NET related directories and not noticed this (no idea how I missed it) I'd given up on that approach.
Anyway... long story short, it was a damaged System.ni.dll that caused my problems, one or more clusters within it had their content replaced with 0x0 and it just so happened to manifest as the odd problem I observed.

This sounds like a timing issue, which the profiler "fixed" by making it just a little slower.
Many profilers use instrumentation (more info here), which slightly slows down the application. Apparently it slows one thread down enough that another thread can do a little bit more work, preventing that crash. Errors like these often do not manifest themselves directly on the developers machine, but surface as soon as they run on a processors with more cores or hyper-threading. Sometimes they only occur in release builds (or vice-versa in debug builds). Timing issues can be difficult to track down since the same code may give different results in different conditions (in profiler or debugger).
From your description I'll attempt to do a wild guess on how it may be fixed:
Try to find in the source where the new threads are started. Then after they are spawned add a System.Threading.Thread.Sleep(500); line there to pause the main thread and give the new threads some time to start.
Without the source code and a few stack traces of the crashes, this is quite a bit of guesswork.

Testing and debuggin application crashes C#

I have an application that after a few times if running it crashes. (application not responding).
when I try to attach my code to process I get assembly debugging, with no helpfull stack trace.
I'm unable to reproduce this from running in VS but only as an application. (therefor intellitrace - which I just read about but not very familiar is irrelevant)
Is there any tool I can use to assist understanding the root cause of the crash
Thanks!

Check the event log or any other logs that your app might be writing to.
Find out if you can narrow down the minimal circumstances to repeat the crash/behavior so you can read the source code to trace the minimal scenario.
If the app does crash when running from VS check whether you are ignoring any exceptions. Look at the Debug | Exceptions dialog and have a look at the output view.
Check your code for Debug.Asserts that are removed from the Release build.

The most common way is to use some kind of Logging system.
Log4Net is very popular these days, you should have a look at it.
Furthermore, if you fix this bug but another one arises on your clients machines, you won't ask them to run a debugger for you, but they can provide you the log file ;-)

The documentation cache is still being constructed... message won't go away in VS 2010

I recently found out that trying to see the documentation on any method or property in Visual Studio just stopped working and it always comes with the message:
The documentation cache is still being constructed. Please try again in a few seconds.
Before, it was just a second and then it worked, now it just won't show the documentation anymore.
How dows this documentation cache works but more important, what can cause it to stop working?.
Any suggestions are welcome. Thanks

The documentation cache is built as a part of idle processing. There are commonly 2 reasons why this operation may never complete
Some other plugin / component is hogging the processor or IDLE queue preventing the documentation cache service from completing.
The documentation is corrupt / deleted from the machine. This is less likely as it's parsing files out of the framework directory.
Most likely case is #1. Have you opened up devenv.exe under task manager and seen if it's actively doing any work?

What could cause a Windows Service to hang when a Console App doing the exact same thing using the exact same base libraries doesn't?

I hate asking questions like this - they're so undefined... and undefinable, but here goes.
Background:
I've got a DLL that is the guts of an application that is a timed process. My timer receives a configuration for the interval at which it runs and a delegate that should be run when the interval elapses. I've got another DLL that contains the process that I inject.
I created two applications, one Windows Service and one Console Application. Each of the applications read their own configuration file and load the same libraries pushing the configured timer interval and delegate into my timed process class.
Problem:
Yesterday and for the last n weeks, everything was working fine in our production environment using the Windows Service. Today, the Windows Service will run for a period of around 20-30 minutes and hangs (with a timer interval of 30 secods), but the console application runs without issue and has for the past 4 hours. Detailed logging doesn't indicate any failure. It's as if the Windows Service just...dies quietly - without stopping.
Given that my Windows Service and Console Applications are doing the exact same thing, I can only think that there is something that is causing the Windows Service process to hang - but I have no idea what could be causing that. I've checked the configuration files, and they're both identical - I even copied and pasted the contents of one into the other just to be sure. No dice.
Can anyone make suggestions as to what might cause a Windows Service to hang, when a counterpart Console Application using the same base libraries doesn't; or can anyone point me in the direction of tools that would allow me to diagnose what could be causing this issue?
Thanks for everyone's help - still digging.

You need to figure out what changed on the production server. At first, the IT guys responsible will swear that nothing changed but you have to be persistent. i've seen this happen to often i've lost count. Software doesn't spoil. Period. The change must have been to the environment.
Difference in execution: You have two apps running the same code. The most likely difference (and culprit) is that the service is running with a different set of security credentials than your console app and might fall victim to security vagaries. Check on that first. Which Windows account is running the service? What is its role and scope? Is there any 3rd party security software running on the server and perhaps Killing errant apps? Do you have to register your service with a 3rd party security service? Is your .Net assembly properly signed? Are your .Net assemblies properly registered and configured on the server? Last but not least, don't forget that a debugger user, which you most likely are, gets away with a lot more stuff than many other account types.
Another thought: Since timing seems to be part of the issues, check the scheduled tasks on the machine. Perhaps there's a process that is set to go off every 30 minutes that is interfering with your own.

You can debug a Windows service by running it interactively within Visual Studio. This may help you to isolate the problem by setting (perhaps conditional) breakpoints.
Alternatively, you can use the Visual Studio "Attach to process" dialog window to find the service process and attach to it with the "Debug CLR" option enabled. Again this allows you to set breakpoints as needed.
Are you using any assertions? If an assertion fires without being re-directed to write to a log file, your service will hang. If the code throws an unhandled exception, perhaps because of a memory leak, then your service process will crash. If you set the Service Control Manager (SCM) to restart your process in the event of a crash, you should be able to see that the service has been restarted. As you have identical code running in both environments, these two situations don't seem likely. But remember that your service is being hosted by the SCM, which means a very different environment to the one in which your console app is running.
I often use a "heartbeat", where each active thread in the service sends a regular (say every 30 seconds) message to a local MSMQ. This enables manual or automated monitoring, and should give you some clues when these heartbeat messages stop arriving.
Annother possibility is some sort of permissions problem, because the service is probably running with a different local/domain user to the console.
After the hang, can you use the SCM to stop the service? If you can't, then there is probably some sort of thread deadlock problem. After the service appears to hang, you can go to a command-line and type sc queryex servicename. This should give you the current STATE of the service.

I would probably put in some file logging just to see how far the program is getting. It may give you a better idea of what is looping/hanging/deadlocked/crashing.

You can try these techniques
Logging start logging the flow of the code in the service. Have this parameter based so you dont have a deluge after you are done. You should log all function names, parameters, timestamps.
Attach Debugger Locally or Remotely attach a debugger with the code to the running service, set appropriate breakpoints (can be based on the data gathered from logging)
PerfMon Run this utility and gather information about the machine that the service is running on for any additional clues (high CPU spikes, IO spikes, excessive paging, etc)

Microsoft provides a good resource on debugging a Windows Service. That essentially sounds like what you'd have to do given that your question is so generic. With that said, has any changes been made to the system over the last few days that could aversely affect the service? Have you made any updates to the code that change the way the service might possibly work?
Again, I think you're going to have to do some serious debugging to find your problem.

What type of timer are you using in the windows service? I've seen numberous people on SO have problems with timers and windows services. Here is a good tutorial just to make sure you are setting it up correctly and using the right type of timer. Hope that helps.

Another potential problem in reference to psasik's answer is if your application is relying on something only available when being run in User Mode.
Running in service mode runs in (is it desktop0?) which can cause some issues in my experience if you are trying to determine states of something that can only be seen in user mode.

Smells like a threading issue to me. Is there any threading or async work being done at all? One crucial question is "does the service hang on the same line of code or same method every time?" Use your logging to find out the last thing that happens before a hang, and if so, post the problem code.
One other tool you may consider is a good profiler. If it is .NET code, I believe RedGate ANTS can monitor it and give you a good picture of any threadlock scenarios.

How to debug leaking connections in an ASP.NET 2.0 Web Services application?

I have an app, which is a bunch of c# web services sitting on top of ASP.NET 2.0 in IIS7 on Win2k3. Following the last release, we keep getting connection timeouts. A quick investigation using Perfmon confirmed that our application is leaking connections.
However, there have been so many code changes in the last release, that it is really difficult to determine where the problem is just by looking at code changes.
Is there a way to debug where the connection leaks are actually occurring?

You can use performance counters to check the memory leaks.
See this link:
http://msdn.microsoft.com/en-us/library/fxk122b4.aspx
It can say whether your application is having memory leaks or not? But it will not find
the code which is causing that things. For that you have to debug the application.