WPF's ContextMenu causes memory leak in ctfmon.exe

Question

WPF's ContextMenu causes memory leak in ctfmon.exe

黎庆文 0

Hi. In WPF, if the control right clicks and creates a new ContextMenu every time, too many times can lead to memory leaks in ctfmon.exe
Here is my example code：
private void TestButton_MouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)

{

if (e.RightButton == System.Windows.Input.MouseButtonState.Pressed)

{

if (contextMenu != null && contextMenu.IsOpen)

{

contextMenu.IsOpen = false;

contextMenu = null;

}

contextMenu = new ContextMenu();

MenuItem menuItem = new MenuItem { Header = "Test Menu Item" };

menuItem.Click += (s, args) => MessageBox.Show("Menu Item Clicked");

contextMenu.Items.Add(menuItem);

contextMenu.IsOpen = true;

contextMenu.Placement = System.Windows.Controls.Primitives.PlacementMode.Bottom;

}

I use the mouse click tool to simulate right clicking with the mouse, clicking ten times per second. The memory of ctfmon.exe will increase by about 1MB per minute.
Does anyone know the reason for this? It's very important to me.

Viorel 124.9K

The fact that there is no “-=” to unsubscribe from the event could be causing the leaks inside the C# programs in certain circumstances, but it seems that your issue is different.

In any case, to avoid suspicion, try to modify the code:

// creating the menu item:
MenuItem menuItem = new MenuItem { Header = "Test Menu Item" };
menuItem.Click += MyHandler;
. . .

// when menu is closed:
( (MenuItem)contextMenu.Items[0] ).Click -= MyHandler;
contextMenu = null;
. . .

// the handler:
void MyHandler( object sender, RoutedEventArgs e )
{
    MessageBox.Show( "Menu Item Clicked" );
}

2 answers

Your answer

Viorel 124.9K Reputation points

2025-09-26T10:35:42.9633333+00:00

The fact that there is no “-=” to unsubscribe from the event could be causing the leaks inside the C# programs in certain circumstances, but it seems that your issue is different.

In any case, to avoid suspicion, try to modify the code:

// creating the menu item: MenuItem menuItem = new MenuItem { Header = "Test Menu Item" }; menuItem.Click += MyHandler; . . . // when menu is closed: ( (MenuItem)contextMenu.Items[0] ).Click -= MyHandler; contextMenu = null; . . . // the handler: void MyHandler( object sender, RoutedEventArgs e ) { MessageBox.Show( "Menu Item Clicked" ); }

Answer 1

Michael Le (WICLOUD CORPORATION) 3,495 Microsoft External Staff

Hello 黎庆文,

Thank you for reaching out.

Creating a new ContextMenu for every single right-click seems inefficient.

Each time you create a new ContextMenu, it allocates not just managed memory in your app, but also unmanaged resources within these Windows services.

When you create and destroy menus very quickly, the system can't clean up these resources fast enough. This leads to a gradual memory buildup in ctfmon.exe.

The best practice is to create a single ContextMenu once and reuse it.

I hope this helps. If my answer is useful, please consider marking it as final.

Thank you.

黎庆文 0 Reputation points

2025-09-26T07:41:29.49+00:00

Hello，Thank you very much for responding to my question.

My WPF program needs to run for a long time, and the system will constantly create and destroy these controls, so there will be a lot of contextMenu generated.This problem arises after the system has been running for a long time.

Actually, after running my system for a long time, a Windows Script Host pop-up window will appear with the following content:“Windows Script Host initialization failed. (There is not enough memory to complete this operation.)”.
Even if I restart my WPF program, this exception still persists.

I checked the memory,Handle, GDI handle, User handle. These data all seem normal. It seems that only ctfmon. exe has a relatively large amount of memory in the system. Could it be this that caused my WPF program to crash?
Michael Le (WICLOUD CORPORATION) 3,495 Reputation points Microsoft External Staff

2025-09-26T08:13:51.3733333+00:00

Thank you for the follow-up.

Could it be this that caused my WPF program to crash?

Yes, it is highly likely that this leak is the cause.

Because ctfmon.exe is a shared system process, it does not terminate with your WPF application. Consequently, the leaked memory is not recovered until the system is rebooted.

You would need to fix the leak first. If the problem still persists after that, please let me know.
黎庆文 0 Reputation points

2025-09-26T08:35:24.69+00:00

Thank you very much for your suggestion.

Sorry, I'm not very familiar with the working mechanism of ctfmon.exe

Finally, another question, can a memory leak in ctfmon. exe cause the WPF program to throw the error "There is not enough memory to complete this operation"?

When my program encountered an error, the total memory usage of the operating system was less than 40%. However, at this time, my program and some of the built-in management windows in Windows could not be opened properly.

Upon checking the system logs, The log error stack is as follows：

System.ComponentModel.Win32Exception (0x80004005):There is not enough memory to complete this operation.

in MS.Win32.UnsafeNativeMethods.RegisterClassEx(WNDCLASSEX_D wc_d)

in MS.Win32.HwndWrapper..ctor(Int32 classStyle, Int32 style, Int32 exStyle, Int32 x, Int32 y, Int32 width, Int32 height, String name, IntPtr parent, HwndWrapperHook[] hooks)

in System.Windows.Threading.Dispatcher..ctor()

in System.Windows.Threading.Dispatcher.get_CurrentDispatcher()

in System.Windows.Input.StylusPlugIns.DynamicRendererThreadManager.DynamicRendererThreadManagerWorker.InkingThreadProc()

in System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

in System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)

in System.Threading.ThreadHelper.ThreadStart()

Could this error be caused by ctfmon. exe?

Looking forward to your reply very much.
Michael Le (WICLOUD CORPORATION) 3,495 Reputation points Microsoft External Staff

2025-09-26T09:35:10.0566667+00:00

Thank you for the follow-up.

Yes, the leak could cause a lot of problems.

The memory leak isn't consuming your RAM, but a limited memory pool called the desktop heap.

MS.Win32.UnsafeNativeMethods.RegisterClassEx is a function that "registers" a new type of window before it can be shown. This registration information is stored in the desktop heap - which is being consumed by ctfmon.exe.

Other management windows also failed to open—they also need to access the depleted desktop heap and couldn't.
黎庆文 0 Reputation points

2025-09-26T09:55:17.2833333+00:00

Thank you very much for your suggestion.

Is there any way to check the usage of the desktop heap in Windows?
Michael Le (WICLOUD CORPORATION) 3,495 Reputation points Microsoft External Staff

2025-09-26T10:18:29.9066667+00:00

Thank you for the follow-up question.

Unfortunately, Windows does not provide a built-in utility for directly monitoring desktop heap usage.

However, you can gain indirect insight by using a tool like Microsoft's Process Explorer. While it does not display desktop heap consumption as a direct metric, it allows you to track related resource counts.

Within Process Explorer, you can monitor the number of USER Objects and GDI Objects allocated by a process. A rapid or sustained increase in these values is a strong indicator of a resource leak that is consuming the finite desktop heap.
Michael Le (WICLOUD CORPORATION) 3,495 Reputation points Microsoft External Staff

2025-10-03T03:27:36.64+00:00

Hello @黎庆文 , please let me know if you have any other questions.
Michael Le (WICLOUD CORPORATION) 3,495 Reputation points Microsoft External Staff

2025-10-13T08:05:24.3133333+00:00

Hello,

It's been a while since I last heard from you. Hope things are going well.

If you're still interested or have any questions, I’d be happy to help. Feel free to reach out whenever it suits you.

Answer 2

Is there any way to check the usage of the desktop heap in Windows?

You can use Debugger Commands !heap extension to display heap usage information, control breakpoints in the heap manager, detect leaked heap blocks, search for heap blocks, or display page heap information.

This extension supports the segment heap and the NT heap. Use !heap with no parameter to list all heaps and their type.

You can also use Desktop Heap Diagnostic Tool to help diagnose Desktop Heap Exhaustion issues. DesktopHeapDiag can probe the various Desktop Heaps and display their current usage %.

Hope it can help you.

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WPF's ContextMenu causes memory leak in ctfmon.exe

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