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Exception is thrown when closing RiibonForm with TabbedMDIManager who's children have cmbAdv1 activated

I have a project where I have Main mdi form which is of Type Ribbon.
There is TabbedMDIManager control on that MainForm which RibbonStyle is set to TouchStyle.
I have a separate child form which is inherits from MetroForm.
I have combboxadv1 set to Metro style on that child form. comboboxadv1 is empty and doesn't contain items.
When I run application and put two or more ChildForms in TabbedMDIManager.
After that I click for example on second tab to activate form. After that comboboxadv1 gets focus and become active (text within becomes blue).
After that I click on Close button on MainForm to close whole application and than following error message is thrown:
An unhandled exception of type 'System.NullReferenceException' occurred in Syncfusion.Shared.Base.dll
Additional information: Object reference not set to an instance of an object.
System.NullReferenceException was unhandled
Message=Object reference not set to an instance of an object.
at Syncfusion.Windows.Forms.Tools.ComboDropDown.InitDropDownButton(DropDownButton ddButton)
at Syncfusion.Windows.Forms.Tools.ComboDropDown.Init()
at Syncfusion.Windows.Forms.Tools.ComboBoxBase.OnHandleCreated(EventArgs e)
at System.Windows.Forms.Control.WmCreate(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at Syncfusion.Windows.Forms.Tools.ComboDropDown.WndProc(Message& m)
at Syncfusion.Windows.Forms.Tools.ComboBoxAdv.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
If I set Style to comboBoxAdv1 to Default then app closes without error message.
Is this normal behaviour?
Please help.

6 Replies

SY SysNop November 13, 2015 09:21 AM UTC

I am attaching video where you can see what i am talkling about.
I used your showcase example TabbedMDI_2015 to demonstrate error in attached video.

Thank You.

Attachment: Error_message_video_c0ff13eb.zip

SK Senthil Kumaran Rajan Syncfusion Team November 16, 2015 01:02 PM UTC

HI SysNop,

Thank you for contacting Syncfusion support.

We are unable to reproduce the reported behavior at our end, we have prepared the sample and the video for your reference and it can be downloaded from the below location.

Sample : http://www.syncfusion.com/downloads/support/forum/121136/ze/TabbedMDI-1012920238

Video : http://www.syncfusion.com/downloads/support/forum/121136/ze/ComboBoxNull-2041678575

Could you check with the above sample and let us know if you are able to reproduce the reported behavior? if not please modify the sample that could reproduce the reported behavior and additionally please share us the version details you are using currently. It will be helpful for us to analyze and provide you a prompt solution.


SY SysNop November 16, 2015 01:35 PM UTC

I am using VS 2015 and I run VS2015sln in example in attachment.
I get an error when did these steps:
1. Run app
2. I go to File menu and select New Document --> I do that twice
3. After that I click with mouse inside combobox to get focus
4. Click on X to close app
After that, error message pops up

I attached video so you can see.

Attachment: Error_message_video_1_dcf6a061.zip

SK Senthil Kumaran Rajan Syncfusion Team November 17, 2015 11:44 AM UTC

Hi SysNop,

Thank you for your update.

We have considered this behavior with “ComboBoxAdv” as bug and a support incident has been created under your account to track the status of this requirement. Please log on to our support website to check for further updates.



SY SysNop December 23, 2015 02:44 PM UTC

I cant't find nothing regarding this issue in Direct-Trac Support System?
Is this solved or?


SK Senthil Kumaran Rajan Syncfusion Team December 24, 2015 05:11 AM UTC

Hi SysNop,

Thank you for your update.

We had re-opened the incident again in order to provide complete solution. Please follow-up with incident for further assistance.


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