How to fix the Runtime Code 4012 Cannot explicitly modify Children collection of Panel used as ItemsPanel for ItemsControl

Symptoms of Code 4012 - Cannot explicitly modify Children collection of Panel used as ItemsPanel for ItemsControl

Runtime errors happen without warning. The error message can come up the screen anytime Microsoft Silverlight is run. In fact, the error message or some other dialogue box can come up again and again if not addressed early on.

There may be instances of files deletion or new files appearing. Though this symptom is largely due to virus infection, it can be attributed as a symptom for runtime error, as virus infection is one of the causes for runtime error. User may also experience a sudden drop in internet connection speed, yet again, this is not always the case.

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Causes of Cannot explicitly modify Children collection of Panel used as ItemsPanel for ItemsControl - Code 4012

During software design, programmers code anticipating the occurrence of errors. However, there are no perfect designs, as errors can be expected even with the best program design. Glitches can happen during runtime if a certain error is not experienced and addressed during design and testing.

Runtime errors are generally caused by incompatible programs running at the same time. It may also occur because of memory problem, a bad graphics driver or virus infection. Whatever the case may be, the problem must be resolved immediately to avoid further problems. Here are ways to remedy the error.

Repair Methods

Runtime errors may be annoying and persistent, but it is not totally hopeless, repairs are available. Here are ways to do it.

If a repair method works for you, please click the upvote button to the left of the answer, this will let other users know which repair method is currently working the best.

Please note: Neither ErrorVault.com nor it's writers claim responsibility for the results of the actions taken from employing any of the repair methods listed on this page - you complete these steps at your own risk.

Method 1 - Close Conflicting Programs

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When you get a runtime error, keep in mind that it is happening due to programs that are conflicting with each other. The first thing you can do to resolve the problem is to stop these conflicting programs.

• Open Task Manager by clicking Ctrl-Alt-Del at the same time. This will let you see the list of programs currently running.
• Go to the Processes tab and stop the programs one by one by highlighting each program and clicking the End Process buttom.
• You will need to observe if the error message will reoccur each time you stop a process.
• Once you get to identify which program is causing the error, you may go ahead with the next troubleshooting step, reinstalling the application.

Method 2 - Update / Reinstall Conflicting Programs

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Using Control Panel

• For Windows 7, click the Start Button, then click Control panel, then Uninstall a program
• For Windows 8, click the Start Button, then scroll down and click More Settings, then click Control panel > Uninstall a program.
• For Windows 10, just type Control Panel on the search box and click the result, then click Uninstall a program
• Once inside Programs and Features, click the problem program and click Update or Uninstall.
• If you chose to update, then you will just need to follow the prompt to complete the process, however if you chose to Uninstall, you will follow the prompt to uninstall and then re-download or use the application's installation disk to reinstall the program.

Using Other Methods

• For Windows 7, you may find the list of all installed programs when you click Start and scroll your mouse over the list that appear on the tab. You may see on that list utility for uninstalling the program. You may go ahead and uninstall using utilities available in this tab.
• For Windows 10, you may click Start, then Settings, then choose Apps.
• Scroll down to see the list of Apps and features installed in your computer.
• Click the Program which is causing the runtime error, then you may choose to uninstall or click Advanced options to reset the application.

Method 3 - Update your Virus protection program or download and install the latest Windows Update

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Virus infection causing runtime error on your computer must immediately be prevented, quarantined or deleted. Make sure you update your virus program and run a thorough scan of the computer or, run Windows update so you can get the latest virus definition and fix.

Method 4 - Re-install Runtime Libraries

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You might be getting the error because of an update, like the MS Visual C++ package which might not be installed properly or completely. What you can do then is to uninstall the current package and install a fresh copy.

• Uninstall the package by going to Programs and Features, find and highlight the Microsoft Visual C++ Redistributable Package.
• Click Uninstall on top of the list, and when it is done, reboot your computer.
• Download the latest redistributable package from Microsoft then install it.

Method 5 - Run Disk Cleanup

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You might also be experiencing runtime error because of a very low free space on your computer.

• You should consider backing up your files and freeing up space on your hard drive
• You can also clear your cache and reboot your computer
• You can also run Disk Cleanup, open your explorer window and right click your main directory (this is usually C: )
• Click Properties and then click Disk Cleanup

Method 6 - Reinstall Your Graphics Driver

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If the error is related to a bad graphics driver, then you may do the following:

• Open your Device Manager, locate the graphics driver
• Right click the video card driver then click uninstall, then restart your computer

Method 7 - IE related Runtime Error

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If the error you are getting is related to the Internet Explorer, you may do the following:

1. Reset your browser.
• For Windows 7, you may click Start, go to Control Panel, then click Internet Options on the left side. Then you can click Advanced tab then click the Reset button.
• For Windows 8 and 10, you may click search and type Internet Options, then go to Advanced tab and click Reset.
2. Disable script debugging and error notifications.
• On the same Internet Options window, you may go to Advanced tab and look for Disable script debugging
• Put a check mark on the radio button
• At the same time, uncheck the "Display a Notification about every Script Error" item and then click Apply and OK, then reboot your computer.

If these quick fixes do not work, you can always backup files and run repair reinstall on your computer. However, you can do that later when the solutions listed here did not do the job.

Other languages:

Wie beheben Fehler 4012 (Die untergeordnete Sammlung von Panel, die als ItemsPanel für ItemsControl verwendet wird, kann nicht explizit geändert werden) - Die untergeordnete Auflistung von Panel, die als ItemsPanel für ItemsControl verwendet wird, kann nicht explizit geändert werden. ItemsControl generiert untergeordnete Elemente für Panel.
Come fissare Errore 4012 (Impossibile modificare in modo esplicito la raccolta Children di Panel utilizzata come ItemsPanel per ItemsControl) - Impossibile modificare in modo esplicito la raccolta Children di Panel usata come ItemsPanel per ItemsControl. ItemsControl genera elementi figlio per Panel.
Hoe maak je Fout 4012 (Kan de onderliggende verzameling van paneel die wordt gebruikt als ItemsPanel voor ItemsControl niet expliciet wijzigen) - Kan de onderliggende verzameling van Panel die wordt gebruikt als ItemsPanel voor ItemsControl niet expliciet wijzigen. ItemsControl genereert onderliggende elementen voor Panel.
Comment réparer Erreur 4012 (Impossible de modifier explicitement la collection Children de Panel utilisée comme ItemsPanel pour ItemsControl) - Impossible de modifier explicitement la collection Children de Panel utilisée comme ItemsPanel pour ItemsControl. ItemsControl génère des éléments enfants pour Panel.
어떻게 고치는 지 오류 4012 (ItemsControl의 ItemsPanel로 사용되는 Panel의 Children 컬렉션을 명시적으로 수정할 수 없습니다.) - ItemsControl의 ItemsPanel로 사용되는 Panel의 Children 컬렉션을 명시적으로 수정할 수 없습니다. ItemsControl은 Panel에 대한 자식 요소를 생성합니다.
Como corrigir o Erro 4012 (Não é possível modificar explicitamente a coleção Children do Panel usado como ItemsPanel para ItemsControl) - Não é possível modificar explicitamente a coleção Children do Panel usada como ItemsPanel para ItemsControl. ItemsControl gera elementos filho para Panel.
Hur man åtgärdar Fel 4012 (Kan inte explicit modifiera Children-samling av panel som används som ItemsPanel för ItemsControl) - Kan inte uttryckligen ändra barns samling av panel som används som ItemsPanel för ItemsControl. ItemsControl genererar underordnade element för panelen.
Как исправить Ошибка 4012 (Невозможно явно изменить дочернюю коллекцию Panel, используемую в качестве ItemsPanel для ItemsControl) - Невозможно явно изменить дочернюю коллекцию Panel, используемую в качестве ItemsPanel для ItemsControl. ItemsControl создает дочерние элементы для Panel.
Jak naprawić Błąd 4012 (Nie można jawnie zmodyfikować kolekcji podrzędnej Panelu używanej jako ItemsPanel dla ItemsControl) - Nie można jawnie zmodyfikować kolekcji podrzędnej Panel używanej jako ItemsPanel dla ItemsControl. ItemsControl generuje elementy podrzędne dla Panelu.
Cómo arreglar Error 4012 (No se puede modificar explícitamente la colección Children del Panel usado como ItemsPanel para ItemsControl) - No se puede modificar explícitamente la colección Children del Panel usado como ItemsPanel para ItemsControl. ItemsControl genera elementos secundarios para Panel.

About The Author: Phil Hart has been a Microsoft Community Contributor since 2010. With a current point score over 100,000, they've contributed more than 3000 answers in the Microsoft Support forums and have created almost 200 new help articles in the Technet Wiki.

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