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Random exceptions in Windows Forms app Messages   Related Types This message was discovered on microsoft.public.dotnet.framework.windowsforms. Post a new message to this list... Brian Eng We are working on a large project that has several owner-drawn controls and interacts with a couple of COM components (not ActiveX controls). At seemingly random times, we receive (usually) a NullReferenceException. Occasionally, it is a "External component has thrown an exception". Regardless of the type of exception, we get the following stack trace: at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam) at System.Windows.Forms.NativeWindow.DefWndProc(Message& m) at System.Windows.Forms.Control.DefWndProc(Message& m) at System.Windows.Forms.Control.WmUpdateUIState(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ScrollableControl.WndProc(Message& m) at System.Windows.Forms.ContainerControl.WndProc(Message& m) at System.Windows.Forms.ParkingWindow.WndProc(Message& m) at System.Windows.Forms.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) Our QA team has been unable to find a reproducable path. Any ideas? Reply to this message...        Sijin Joseph Ensure that your windows form App and them COM compoenents are using compatible Threading models. By default all winform apps use the STA threading model. If your COM components are MTA threaded then you could such kind of exceptions. -- Sijin Joseph http://www.indiangeek.net http://weblogs.asp.net/sjoseph "Brian Eng" <Click here to reveal e-mail address> wrote in message news:Click here to reveal e-mail address... > We are working on a large project that has several owner-drawn controls and [Original message clipped] Reply to this message...        Brian Eng Thanks for your reply. That is really interesting... Unfortunately, our WinForms app and all COM components are STA. Any other ideas? "Sijin Joseph" wrote: [Original message clipped] Reply to this message...        Brian Eng Ok, we are getting to the root of the problem. We are using Spy++ to view the parked window handles that are being created by our application. It seems that when you create a panel that is not initially visible, its child controls are initially parked. When you then close the containing form, those child controls are not properly disposed. Anyone seen this before? "Brian Eng" wrote: [Original message clipped] Reply to this message...        Charles Collins I have an application that is throwing the same error, but only when run through terminal server. We have yet to see it in any other instance and it is totally random and sporadic. A solution to this issue would be greatly welcomed here too. "Brian Eng" <Click here to reveal e-mail address> wrote in message news:Click here to reveal e-mail address... [Original message clipped] Reply to this message...     System.IntPtr System.NullReferenceException System.Windows.Forms.ContainerControl System.Windows.Forms.Control System.Windows.Forms.NativeWindow System.Windows.Forms.ScrollableControl Ad MBR BootFX Best-of-breed application framework for .NET projects, developed by Matthew Baxter-Reynolds and MBR IT

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