Onpaint Error
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Hargreaves - MSFTNovember 22, 201011 Share 0 0 You are making a WinForms app. All is going well, until one day your custom control disappears. In its place you just see a big red cross: What gives? Let us back up to doom 2016 unhandled exception remind ourselves how exceptions work: If your code does something wrong (such as dereferencing
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a null object or passing invalid parameters to an API) an exception is thrown If your code catches the exception, it doom 4 unhandled exception can handle the error and continue along its merry way If the exception is not caught, the program terminates If the debugger is attached when an unhandled exception occurs, it pops up a window big green tick showing the exception message and callstack, so you can see exactly what went wrong WinForms extends this system in one important way: It wraps calls to your Control.OnPaint method in a try/catch block If OnPaint throws an exception, this is now caught by WinForms rather than left unhandled WinForms keeps track of whether OnPaint has ever thrown an exception If so, it skips any later calls to OnPaint,
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and instead just draws a red cross I don't know why WinForms decided to do this, but it's kinda annoying because if anything goes wrong in your OnPaint code, the debugger never gets to see the exception so has no chance to show you the exception message! To debug such problems, open up the Debug \ Exceptions menu in Visual Studio and check the Thrown box next to Common Language Runtime Exceptions. Now the debugger will break whenever any exception is thrown, regardless of whether or not it is caught further up the stack, so you can see the original message and callstack in spite of WinForms trying to catch this error. Comments (11) Cancel reply Name * Email * Website Michael Cummings says: November 22, 2010 at 12:52 pm I'm not as interested in the content of the post as much as to *why* you posted this? What cool new Xna features that Shawn is working on requires a Winform Custom Control? Reply Cygon says: November 22, 2010 at 12:54 pm I think the reason probably is because OnPaint() is being called from within the Windows message loop (or more specifically, the WndProc callback) and WinForms can't just let the exception travel upwa
resources Windows Server 2012 resources Programs MSDN subscriptions Overview Benefits Administrators Students Microsoft Imagine Microsoft Student Partners ISV Startups TechRewards Events Community Magazine Forums Blogs Channel 9 Documentation APIs and reference Dev centers Samples Retired content We’re sorry. The content https://blogs.msdn.microsoft.com/shawnhar/2010/11/22/winforms-and-the-big-red-x-of-doom/ you requested has been removed. You’ll be auto redirected in 1 second. System.Windows.Forms Control Class Control Methods Control Methods OnPaint Method OnPaint Method OnPaint Method AccessibilityNotifyClients Method BeginInvoke Method BringToFront Method Contains Method CreateAccessibilityInstance Method CreateControl https://msdn.microsoft.com/en-us/library/system.windows.forms.control.onpaint(v=vs.110).aspx Method CreateControlsInstance Method CreateGraphics Method CreateHandle Method DefWndProc Method DestroyHandle Method Dispose Method DoDragDrop Method DrawToBitmap Method EndInvoke Method FindForm Method Focus Method FromChildHandle Method FromHandle Method GetAccessibilityObjectById Method GetAutoSizeMode Method GetChildAtPoint Method GetContainerControl Method GetNextControl Method GetPreferredSize Method GetScaledBounds Method GetStyle Method GetTopLevel Method Hide Method InitLayout Method Invalidate Method Invoke Method InvokeGotFocus Method InvokeLostFocus Method InvokeOnClick Method InvokePaint Method InvokePaintBackground Method IsInputChar Method IsInputKey Method IsKeyLocked Method IsMnemonic Method MemberwiseClone Method NotifyInvalidate Method OnAutoSizeChanged Method OnBackColorChanged Method OnBackgroundImageChanged Method OnBackgroundImageLayoutChanged Method OnBindingContextChanged Method OnCausesValidationChanged Method OnChangeUICues Method OnClick Method OnClientSizeChanged Method OnContextMenuChanged Method OnContextMenuStripChanged Method OnControlAdded Method OnControlRemoved Method OnCreateControl Method OnCursorChanged Meth
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings http://stackoverflow.com/questions/33281685/fillpie-in-onpaint-caussing-an-error-after-minimizinig and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation https://www.syncfusion.com/forums/21593/object-error-in-onpaint Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join them; it unhandled exception only takes a minute: Sign up FillPie() in OnPaint caussing an error after minimizinig up vote 0 down vote favorite I've encountered a problem with handling OnPaint event. I have a custom class: namespace WinFormsConsumer { public class Cookie { public Point Point{get; set;} public Color Color { get; set; } public int Angle { get; set; } public Cookie(Point doom 2016 unhandled point, Color color, int angle) { Point = point; Color = color; Angle = angle; } } } I also defined helper method (taken from class PaintService taken from WebService): public Nullable
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