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I'm now working on some pretty big application with really nasty code. The problem is that from time to time the whole GUI of the app is freezing and stops responding (and after some time Windows wants to take the app down). I have a really big problem to even look where to debug the app, mostly because when this thing happens and I pause it in the VS debugger, it highlight the line:

CardWindow.ShowDialog();

It's not helpfull at all. Also when this thing happens it tends to grow the app size in the memory, ocasionally throwing OutOfMemoryException.

I also checked whether it might be some kind of an infinite loop in one of created threads, but VS shows me that only the main thread is active, and the rest are either ended or not running at all (the thread implememtation is also really poorly written).

The application uses remote objects within local networks, and some threads are used to transfer photos and other data from clients to server, but I don't know how to check if this is what it's causing it. But when the server app hangs, the clients are still fully capable to connect with it.

Short info of how it's made: the app uses Firebird engine to store its data. The DB is on the server machine, and the clients are connected via local LAN to it using standard Firebird C# library, and the app instances communicates with each other using remote object (the server is also a client).

It's the second week of debugging and I'm getting pretty desperate as I'm getting out of ideas of even how to check what's wrong. The fact that the bug appears randomly also doesn't help.

Can anyone give me some ideas of how to find a trace of this bug?

Using C# .NET 4.5 and WPF with Visual Studio Ultimate 2013 and Firebird 2.5

Lemur
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  • You'll find an example on how to debug a deadlock like that in [this blog post](http://blogs.msdn.com/b/dsui_team/archive/2012/10/31/debugging-windows-forms-application-hangs-during-systemevents.userpreferencechanged.aspx). No, that is not supposed to be easy. Considering structural fixes recommended. – Hans Passant Dec 16 '14 at 00:06

3 Answers3

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I'd suggest using a profiling tool to assist in finding the problem

What Are Some Good .NET Profilers?

Community
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Derek Tomes
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In addition to @DerekTomes. The System.Windows.ShowDialog method, Described in: Window.ShowDialog Method, all other windows are disabled and return only when the window is closed. Check to make sure the window is eventually closed(this.Close() in the CardWindow.xaml.cs or whatever .cs file) or use CardWindow.Show() instead of CardWindow.ShowDialog() so other windows remain running while the CardWindow is running.

CalebB
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I finally figured it out.

When the function that usually hanged the app after 30th run launched, I could see that some of it ran (the window's title changed as it was supposed to). I've found this function and after every single line put:

this.Title = "1";
SomeFunction();
this.Title = "2";
AnotherFunction();
this.Title = "3";
// and so on

I localized what was causing the problem; there was a function that changed the GUI significantly (lots of foo.Visibility and foo.Opacity) and ran in some weird loop. It was fine for the first 20 times to run it, but after 30th it slowed down the app, and after 40th - caused crash.

It now runs only once when it needs to and the problem does not appear. I suppose it caused GUI memory overflow of some kind.

Anyway, thank you for your answers - I ran memory profiling, but it slowed my app down to that point it was impossible to use it.

Lemur
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