How To Fix Error Creating Window Handle

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Fault Creating Window Handle?

Posted 05 January 2017 - 06:26 PM

"System.ComponentModel.Win32Exception was unhandled
Message: An unhandled exception of blazon 'System.ComponentModel.Win32Exception' occurred in System.Windows.Forms.dll
Boosted information: Error creating window handle."

I've only discovered this error occurs later on a catamenia panel had been repopulated too many times.. I read online that it tin happen if components, and their handlers, aren't properly disposed of, then I made this code...

              Public Sub Stats_Destroy_Controls()         Try             For Each cItem Equally Control In Create_Stats_Panel.Controls                 Try                     RemoveHandler cItem.Click, AddressOf [click event]                      HoverText.SetToolTip(cItem, Nothing)                      cItem.Dispose()                 Catch ex As Exception                 End Try             Next         Take hold of ex As Exception         Finish Try          Attempt             Create_Panel.Dispose()         Catch ex As Exception         Stop Effort     End Sub            

Information technology still happens afterwards so long, though.. I also tried to put a "Endeavour" around the populating code in case it's caused by that, only aught is triggered. Am I blatantly stupid, or...?

EDIT: I've done more tests, and no thing how many items I load, even if it's only one component, it all the same throws this fault somewhen.

This post has been edited past ZakaryHansen: 05 January 2017 - 06:56 PM

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#2 maceysoftware

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Re: Fault Creating Window Handle?

Posted 06 January 2017 - 03:36 AM

Hi,

I am not going to say this will set up it however it may exist worth a get.

Instead of just disposing of the command, remove it starting time and then dispose of it, doing this you lot volition have to loop through the controls backwards.

Also tin you bear witness united states of america the code for loading a control?

#3 ZakaryHansen

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Re: Error Creating Window Handle?

Posted 06 January 2017 - 05:nineteen PM

              Dim p Every bit New Panel              Dim l_name As New Label             p.Controls.Add(l_name)             With l_name                 .Location = New Point(23, 0)                 .AutoSize = False                 .Size = New Size(50, 13)                 .TextAlign = ContentAlignment.MiddleLeft                 .AutoEllipsis = True             Terminate With              Dim l_note Every bit New Label             p.Controls.Add together(l_note)             With l_note                 .Location = New Betoken(23, 12)                 .AutoSize = False                 .Size = New Size(50, thirteen)                 .TextAlign = ContentAlignment.MiddleLeft                 .AutoEllipsis = True             End With            

I employ this, but with more than components, and loop through a list of data to populate it.

#iv IronRazer

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Re: Error Creating Window Handle?

Posted 06 January 2017 - 07:03 PM

The cause is probably that your application is trying to create to many handles. There is a limit to the number of handles that can be created past an application. When that limit is hit, you get this same exception.

At least one handle is created for each command that is created in your application but, some controls may actually create several more handles internally, inside the command form which you would non be aware of. There are other things that can create handles that you would non think of without a deeper understanding such as working with File methods, Graphics methods, Bitmaps, and Registry methods just to name a few.

Equally far equally i am aware, there is not a specific magic number of handles that can be created, it will depend on a few different things. Yous can read the two threads below to acquire more than virtually this. The 2nd link is actually a link posted in the outset link.

If this is your problem, then the only mode around it is to apply fewer controls.

What programming practices touch on the number of window handles?
Pushing the Limits of Windows: Handles

#5 ZakaryHansen

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Re: Error Creating Window Handle?

Posted 06 January 2017 - 08:10 PM

That makes sense, to an extent. I mean, if the controls were withal active, I'd understand.. But since they're disposed of, information technology'due south kind of confusing..

But okay, I'll rework the program to keep what it tin, rather than giving information technology the boot every time it refreshes.

Thanks!

EDIT: Is there whatsoever manner to catch this fault? If it yet happens, I'd like the user's work to be saved rather than being lost.

This mail has been edited by ZakaryHansen: 06 January 2017 - 08:xiv PM

#six maceysoftware

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Re: Fault Creating Window Handle?

Posted 07 Jan 2017 - 03:41 AM

OK I see where IronRazor is going with this and it is fairly piece of cake to just check if this is the issue.

Now first thing I desire to indicate out, is that this method to find the handles count should not be relied upon autonomously from getting a crude guide of how many handles are created.

If yous open up Task Manager, and get across to processes (details in windows 10 perchance eight as well) right click the column headers and choose the 'Select Columns' select 'GDI Objects' and 'User Objects'.

This volition show y'all how many GDI objects each application is ROUGHLY using at the time.

Now at any given time your computer can use upwardly to a theoretical maximum of 65,536 GDI object, Yet there is another limit of a per application limit of 10,000, because well you don't want one application to bring your whole figurer crashing to its knees exercise you, if y'all want to see what can happen to a estimator if the GDI limit is reached employ IronRazors second link and go to the article 'pushing the limits of windows user and gdi objects role 2'. At that place are some images there showing what can happen. As well worth while studying the whole of that blog every bit information technology is what I studied when I was looking into this.

So what happens when a application reaches its limit? you lot ordinarily become a mistake message and your application crashes. Commonly application should never even get to 10,000 in fact typically application shouldn't even achieve half of that.

Sadly I am currently working on a application which can hands reach this limit, all the same I have washed a lot of work around the cosmos of controls and the handling of them through their life-cycle up until their disposal and so that this limit is hardly ever reached now.

So what if your application is using over 10,000 GDI objects? then your application either has too many controls at ane given fourth dimension, or your non clearing upward something well enough.

Here is a list of my biggest pains when I was sorting out issues, some peradventure helpful.

• COM Calls - So we were using a COM Telephone call to get images, I can't remember the detail phone call however if you create something in COM then you normally take to dispose of it using COM, normally with a Destroy call. The all-time way to describe this is if you get a handle from COM you volition demand to Destroy information technology.
  
• GDI Cartoon - When creating objects to draw with be it pen, brush or fifty-fifty a font these all create a GDI handle and they won't ever become cleaned away properly if you just let them get out of scope, therefore I e'er recommend using a using block with them.
  
• Handles - Basically if your doing a AddHandler so on the remove and disposal of the control you demand to do a RemoveHandler otherwise the control will not be picked up by the GarbageCollection.

There were a few more however I can't think of anymore at the moment and I don't have VS installed on my home computer at the moment.

That makes sense, to an extent. I mean, if the controls were still active, I'd understand.. But since they're disposed of,            

Just because you have called the dispose doesn't mean they are gone, When you lot call the dispose method sure parts of the control starts to exist cleared away, for example SQLConnection will Close the connection if it is open up on the dispose call, withal the SQLConnection object will be classed and marked every bit disposed notwithstanding the resources including the handle will not be released until the garbage Collector picks information technology up, and so it will but dispose of it if it can, for example if it has a active reference somewhere this may stop this item from existence collected.

You lot should non force the garbage collector to collect unwanted resources, the .Net framework sorts this out for you lot.

Now But for competition at that place is a way to up the application limit through the registry however I am not going to provide links for that as its a horrible solution and one that I believe shouldn't exist done.

#7 IronRazer

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Re: Error Creating Window Handle?

Posted 07 Jan 2017 - 06:53 AM

To exist honest, i never ran into this exception. I`g not certain if it is just my luck or that i have ever been very picky well-nigh disposing and releasing whatever objects i create. Notwithstanding, unlike some other exceptions that can be caught and dealt with, once this exception is raised, i would recollect your app is pretty much done until a Close-North-Restart since you lot can non create whatsoever more handles.

The better way to solve this is to first apply a good resources monitoring blazon program to discover any retention leaks that your application may have and set those get-go. In that location are a few of those programs listed in the link i posted at the bottom of this mail. I would recommend reading through that link besides, it explains more about the causes of retentivity leaks and how to rails them down.

If you exercise that and y'all are even so running into this same exception, then i would rethink the controls that yous are using to display the information to the user.

For instance, if i had 5000 names and addresses to brandish to the user, it would use a large amount of handles and retention to create 5000 labels for each name, 5000 more for each address, and then adding those to 5000 more Panels.

Instead, yous could consider formatting the text to display each name and address in one label. 5000 labels would nevertheless exist a ridiculous amount to apply though. A better option would be using a ListView or DataGridView which is designed for such cases and would not come anywhere well-nigh the handle count and retentiveness usage to brandish the same info. If they would not do, then there is also the pick of creating a small control class that will draw the proper name/address on itself using the OnPaint override. One of those would replace the Panel and the 2 Labels. In that location are more options only, i think you go the signal.

The amount of data that is loaded at any given time is another thought too. If i loaded 200 Bitmap images into a command for the user to view, it would require a lot of retention. Depending on the size of the images displayed to the user they might only be able to encounter maybe 20 at a fourth dimension in the control until they scrolled up/down. The retention usage could be drastically reduced by just loading 20 images at a time to display in the command and giving the user the options to view the (Next Page) or go back to the (Terminal Page). Each time they do this, you lot would release all references to the images in the programme and dispose them as well. And then load and display the Next or Final twenty images.

Anyways, they are just some thoughts and ideas to consider since we don`t actually know the depth of your code and how everything is designed and working in your app. 8)

How to detect and avoid retention and resources leaks in .NET applications

Source: https://www.dreamincode.net/forums/topic/400446-error-creating-window-handle/

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