Adding winform user control 1000 times in a form throws {"error creating window handle."} exception, how to resolve it?

Question

5.00/5 (1 vote)

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1. Winform User control has two panels A, B. A docked to left, B docked to fill.
2. Panel A has two buttons (no events), panel B has two label and two TextBoxes (no events).
3. Adding user control to a Form using given lines, this form has no other control.

public partial class Form1 : Form
    {
        private UserControl1 userControl;
        public Form1()
        {
            InitializeComponent();

            for (int i = 0; i <1000; i++)
            {
                userControl = new UserControl1();
                userControl.Dock = DockStyle.Top;
                Controls.Add(userControl);
            }
        }
    }

4. Given below error occurs at line

Application.Run(new Form1());

, any solution to add large number of user controls to a form?

System.ComponentModel.Win32Exception
  HResult=0x80004005
  Message=Error creating window handle.
  Source=System.Windows.Forms
  StackTrace:
   at System.Windows.Forms.NativeWindow.CreateHandle(CreateParams cp)
   at System.Windows.Forms.Control.CreateHandle()
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl()
   at System.Windows.Forms.Control.WmShowWindow(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmShowWindow(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

What I have tried:

looking for solution to resolve this issue?

Posted 23-Jan-19 9:23am

User 11956321

Updated 23-Jan-19 10:27am

v4

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Comments

MadMyche 23-Jan-19 15:31pm

Why do you need so many controls?

[no name] 23-Jan-19 15:34pm

I just want it, I do not see a reason why I can`t have. Do you have any thought to achieve it? regardless of how imperfect the design is...

Richard MacCutchan 23-Jan-19 15:36pm

You have run out of system resources. There is no valid reason to add that many controls to a form; you need to rethink your design.

[no name] 23-Jan-19 15:43pm

Process Memory stays at 37 MB, CUP uses less than 10<.
I am not an expert but I ran GB size of games on this pc, why this little app is crying?

Richard MacCutchan 23-Jan-19 15:54pm

You have run out of Windows handles most likely. Stop wasting time with this.

Dave Kreskowiak 23-Jan-19 16:32pm

RAM has nothing to do with this. The handle pool in Windows is not unlimited and you ran the pool dry.

You really cannot, in any way at all, add over a thousand controls to a form.

It's not just your app that uses the handle pool. It's every app, window, file, GDI object, device, ..., ..., ... EVERYTHING system-wide in Windows.

In the case of your app, the main form has a handle, the titlebar has a handle, the buttons on it (minimize, maximize, close) all have handles.

Your UserControl uses a minimum of 10 handles, for every instance you create. Congratulations. You just tried to allocate over 10,000 handles in your app, and you wonder why it just went BOOM?

If you exhaust the handle pool, Windows will become very unstable and even crash on you.

[no name] 23-Jan-19 15:48pm

Ask stupid questions; expect stupid answers.

A stupid waste of everyone's time.

[no name] 23-Jan-19 16:42pm

Good observation! And no, I don't think the question is stupid. Knowing the limit of a system (or at least have a feeling for it) is a very good idea.

And for all who think the question is stupid: What is the limit of controls one can add _without_ problems? Aaaah it depends from situation to situation... and what apps are running... :-)

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ZurdoDev · Answer 1 · 2019-01-23T10:12:00

Solution 1

Actually, the error does not quite happen at line "Application.Run(new Form1());". If you were to step IN TO that line, you'd see it is hitting your loop. The error likely means that you have run out of handles. However, you can google the error for other options.

I would write your loop variable (i) out to the debug window so that you can see exactly when it happens. If it happens after 10 iterations, something else is likely going on. But if it is close to 1000, then for sure you are running out of handles.

Posted 23-Jan-19 10:12am

ZurdoDev

Updated 23-Jan-19 14:50pm

v3

Comments

[no name] 23-Jan-19 17:06pm

A 5 for the response.

"Out of handles close to 1000": I think it is important what kind of handles. Skype and a lot of browsers do usually show more than 1000 handles in task manager. I think the problem is on the GDI Objects...

ZurdoDev 23-Jan-19 17:11pm

I just looked closer at the code and OP is creating an infinite loop.

[no name] 23-Jan-19 17:22pm

I don't see an infinite loop ...?

But I think a very big unkown is also "UserControl1", we do not know what "UserControl1" is doing and wheter it is correct.

[no name] 23-Jan-19 19:23pm

public partial class UserControl1 : UserControl
{
public UserControl1()
{
InitializeComponent();
}
}

This is all, UserControl1 doing nothing, as described in question, this user control has panels, buttons, labels and text boxes (details mentioned in question) and no other step at all.

[no name] 23-Jan-19 19:24pm

There is no infinite loop.

ZurdoDev 23-Jan-19 20:50pm

You're right, I misread it. However, the answer is still the same.

ZurdoDev 23-Jan-19 20:49pm

You're right. I just read it again. Somehow I saw the class the code was in as UserControl1 instead of Form1.

[no name] 23-Jan-19 18:07pm

Your [Edit]:
The loop 1...1000 is in Form1 and not in UserControl1 or I'm missing something