We have closed this ticket because another page addresses its subject:
NavigationPane - NullReferenceException is thrown when clicking a navigation tab header twice and setting the State property in the NavigationPane.StateChanged event handlerHi,
I have been using the NavigationPane, in the latest revision 2015 V1.8 a new ShowCollapseButton has been added to remove the collapse button. This is great, but the current page still automatically collapses if the current page tab is selected/clicked again, is there any way to prevent this from happening?
Hello Simon,
Thank you for the project. This behavior occurs because you click on a selected panel again. In this case, this panel will be in the Collapsed state.
To avoid this behavior, you can handle the NavigationPane.StateChanged event and set the NavigationPane.State property manually.
I have modified the project. Try the attached project and let us know if it works for you.
I am looking forward to your response.
Hi Nedezha,
I have tried your application, this works for the first click, however if I click the same panel a second time I get the following exception;
System.NullReferenceException was unhandled
HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=DevExpress.XtraBars.v15.1
StackTrace:
at DevExpress.XtraBars.Navigation.NavigationPaneButtonsPanelHandler.OnMouseDown(MouseEventArgs e)
at DevExpress.XtraBars.Navigation.NavigationPane.DoNCMouseDown(MouseEventArgs e)
at DevExpress.XtraBars.Navigation.NavigationPane.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at TestNavigationPaneCollapse.Program.Main() in C:\Users\Simon\Documents\Visual Studio 2015\Projects\TestNavigationPaneCollapse\TestNavigationPaneCollapse\Program.cs:line 22
at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args)
at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()
InnerException:
So this doesn't offer a solution, I would be happy to go with your solution if we can get rid of the exception.
Hi,
We have successfully reproduced the behavior you described and passed a new NavigationPane - NullReferenceException is thrown when clicking a navigation tab header twice and setting the State property in the NavigationPane.StateChanged event handler ticket to our developers' team for further research. Please bear with us. We will notify you as soon as we make any progress.
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Hello,
I wasn't able to reproduce this behavior with a simple project. Review the attached video and sample. Would you please modify my project to illustrate the issue? This will help us find a solution.
I'm looking forward to your response.
Hi Olga,
Thanks for your reply, I don't think I have explained myself clearly. I was referring to current page tab contents disappearing when a page tab is selected a second time. I would like to prevent this behaviour. I have amended the project you sent to illustrate the issue and included a video which demonstrates my problem.