Memory leak problem

patrick

My program is hitting 500,000k memory and more until it crashes. It uses 50,000k when it first loads. I realized that it climbs in usage and never goes down, and I think I have narrowed the problem down to the way I am switching forms. Here is my code:

if (Properties.Settings.Default.isCashRegister)
{
callerIDTimer.Enabled = false;
if (Functions.IsConnectionAvailable())
{
if (Settings.Default.NumberOfRegisters != 1)
{
var cashRegisterInstance = new cashRegisterForm(Properties.Settings.Default.registerNumber);
}
else
{
var cashRegisterInstance = new cashRegisterForm(1);
Hide();
cashRegisterInstance.Show();
cashRegisterInstance.FormClosed += Instance_FormClosed;
}
}
else
{
MessageBox.Show(Classes.ErrorMessages.ConnectionError1.ToString());
}
}
else
{
MessageBox.Show("Not a cash register station.");
}

Does anyone know where the problem might be?

11 Replies

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Vulpes15y ago
Accepted answer
Well, first of all this bit of code serves no purpose:

if (Settings.Default.NumberOfRegisters != 1)
{
   var cashRegisterInstance = new cashRegisterForm(Properties.Settings.Default.registerNumber);
}

You're creating a new instance of cashRegisterForm and then assigning a reference to it to a local variable which then goes immediately out of scope. This means there is no remaining reference to the form and the GC has to clean it up on the next collection. You could therefore remove this clause completely and relieve some pressure on the GC.

I also have some doubts about the 'else' part:

else
{
   var cashRegisterInstance = new cashRegisterForm(1);
   Hide();
   cashRegisterInstance.Show();
   cashRegisterInstance.FormClosed += Instance_FormClosed;
}

You're creating a new cashRegisterForm instance, hiding the current form, and then showing the new instance. You're also hooking up the new instance's FormClosed event to a handler on the (now) hidden form. If you're not already doing so, it would be better to unhook this handler when the cashRegisterForm is closed in case leaving it hooked has any GC consequences:

private void Instance_FormClosed(Object sender, FormClosedEventArgs e)
{
   var cashRegisterInstance = (cashRegisterForm)sender;
   cashRegisterInstance.FormClosed -= Instance_FormClosed;
   // rest of code
}

Also, rather than creating a new form each time, I suggest it would be better to just use the same instance and show it modally though you may need to clear any content when you close it. You'd then have something like this:

private cashRegisterForm cashRegisterInstance = null; // create private field to hold reference to instance

//...

if (Properties.Settings.Default.isCashRegister)
{
   callerIDTimer.Enabled = false;
   if (Functions.IsConnectionAvailable())
   {
   if (Settings.Default.NumberOfRegisters == 1)
   {
   if (cashRegisterInstance == null)
   {
   cashRegisterInstance = new cashRegisterForm(1);
   }
   cashRegisterInstance.FormClosed += Instance_FormClosed;
   Hide();
   cashRegisterInstance.ShowDialog(); // show modally
   }
   }
   else
   {
   MessageBox.Show(Classes.ErrorMessages.ConnectionError1.ToString());
   }
}
else
{
   MessageBox.Show("Not a cash register station.");
}

I'm not sure whether it will solve your problem but it's worth a try :)
Sam Hobbs15y ago
Without context, I sure cannot figure it out.
patrick15y ago
The offending object is of type byte[]. I can't figure out where this is coming from...
Sam Hobbs15y ago
Use of the using block is good. You probably need to use try/catch more also. It is likely that your program attempts to do something that fails and it does not have a way to get back up.

When it stops responding, does it use processor time?

When you debug the program using a debug build, when it stops responding, try breaking into the program to see what it is doing.
patrick15y ago
Well, I have four external sources of code in my application.
- Onewire.net API which allows employee identification through i-button adapters - this isnt running on any open forms during the problem
- MySQL; every connection is created in a using{} block
- Microsoft Mappoint - the source of many headaches, this runs constantly in the background and the memory climbs without it doing anything.
- GlacialListBox - I dont know who the author of this was, I needed a list box that could list multiple rows of items in a single cell. This could very well be the culprit, as it opens on several of the offending forms.
Vulpes15y ago
If it's the unmanaged part of memory which appears to be leaking, then I suppose the obvious question is: are you doing any interop in your application?

For example COM interop with MS office applications or P/Invoking some unmanaged functions which require you to allocate a block of unmanaged memory first (using Marshal.AllocHGlobal or the COM memory manager). A common error in the latter case is forgetting to call Marshal.FreeHGlobal when you've finished using the memory which will cause a leak.

If ANTS is no help, then you could try JetBrains instead (http://www.jetbrains.com/profiler/).
patrick15y ago
Well maybe there is another problem at the root, but its like I said, the program starts running at around 32mb of memory. After a few hours of heavy use, it is running at 500mb memory. A few hours more and the whole thing just simply stops responding. That doesn't seem right.
Sam Hobbs15y ago
It is totally normal for memory to grow without shrinking if the system does not need more memory. So diagnosis depends heavily on what the error is. You don't say what the error is; you just say crash. It is totally possible that your assumption that memory usage is causing the crash might have distracted you from the path you really need to explore.
patrick15y ago
ANTS shows the unmanaged part of the programs memory allocation growing and growing, but It doesn't provide any detail on what isn't being disposed of.
Vulpes15y ago
Have you tried using a memory profiler on your code?

There's a 14 free trial of the ANTS profiler (http://www.red-gate.com/products/dotnet-development/ants-memory-profiler/?utm_source=google&utm_medium=cpc&utm_content=unmet_need&utm_campaign=antsmemoryprofiler&gclid=CJf_tPOttacCFUtC4QodwGmS-w).
patrick15y ago
I marked you as best answer because i no longer believe this to be the root of the problem, and i appreciate you taking the time to help. I am now almost certain there are objects not being properly disposed of somewhere.