[Mono-bugs] [Bug 352830] New: exe crashes everytime on combo select

[bugzilla_noreply at novell.com]

https://bugzilla.novell.com/show_bug.cgi?id=352830


           Summary: exe crashes everytime on combo select
           Product: Mono: Class Libraries
           Version: 1.2.6
          Platform: 32bit
        OS/Version: Windows XP
            Status: NEW
          Severity: Major
          Priority: P5 - None
         Component: Windows.Forms
        AssignedTo: mono-bugs at lists.ximian.com
        ReportedBy: novell at markandlouise.org.uk
         QAContact: mono-bugs at lists.ximian.com
          Found By: Third Party Developer/Partner


Description of Problem:

Unhandled Exception: System.NullReferenceException: Object reference not set to
an instance of an object
at System.Windows.Forms.ComboBox.DropDownListBoxFinished () [0x00031] in
C:\cygw
in\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\System.W
indows.Forms\ComboBox.cs:1518
at (wrapper remoting-invoke-with-check)
System.Windows.Forms.ComboBox.DropDownLi
stBoxFinished () <0x00038>
at ComboListBox.HideWindow () [0x0001e] in
C:\cygwin\tmp\monobuild\build\BUILD\m
ono-1.2.6\mcs\class\Managed.Windows.Forms\System.Windows.Forms\ComboBox.cs:2252
at ComboListBox.OnMouseUp (System.Windows.Forms.MouseEventArgs) [0x0006a] in
C:\
cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Syst
em.Windows.Forms\ComboBox.cs:2350
at System.Windows.Forms.Control.WmLButtonUp (System.Windows.Forms.Message&)
[0x0
005c] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Window
s.Forms\System.Windows.Forms\Control.cs:5253
at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message&)
[0x0017c
] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Fo
rms\System.Windows.Forms\Control.cs:5006
at ComboListBox.WndProc (System.Windows.Forms.Message&) [0x0002a] in
C:\cygwin\t
mp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\System.Windo
ws.Forms\ComboBox.cs:2419
at ControlWindowTarget.OnMessage (System.Windows.Forms.Message&) [0x00000] in
C:
\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Sys
tem.Windows.Forms\Control.cs:225
at ControlNativeWindow.WndProc (System.Windows.Forms.Message&) [0x00000] in
C:\c
ygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Syste
m.Windows.Forms\Control.cs:206
at System.Windows.Forms.NativeWindow.WndProc
(intptr,System.Windows.Forms.Msg,in
tptr,intptr) [0x0006a] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\cla
ss\Managed.Windows.Forms\System.Windows.Forms\NativeWindow.cs:188
at System.Windows.Forms.XplatUIWin32.InternalWndProc
(intptr,System.Windows.Form
s.Msg,intptr,intptr) [0x0002c] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6
\mcs\class\Managed.Windows.Forms\System.Windows.Forms\XplatUIWin32.cs:1886
at (wrapper native-to-managed)
System.Windows.Forms.XplatUIWin32.InternalWndProc
 (intptr,System.Windows.Forms.Msg,intptr,intptr) <0x00065>
at (wrapper managed-to-native)
System.Windows.Forms.XplatUIWin32.Win32DispatchMe
ssage (System.Windows.Forms.MSG&) <0x00004>
at System.Windows.Forms.XplatUIWin32.DispatchMessage
(System.Windows.Forms.MSG&)
 [0x00000] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.W
indows.Forms\System.Windows.Forms\XplatUIWin32.cs:2081
at System.Windows.Forms.XplatUI.DispatchMessage (System.Windows.Forms.MSG&)
[0x0
0000] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Window
s.Forms\System.Windows.Forms\XplatUI.cs:551
at System.Windows.Forms.Application.RunLoop
(bool,System.Windows.Forms.Applicati
onContext) [0x00359] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class
\Managed.Windows.Forms\System.Windows.Forms\Application.cs:844
at System.Windows.Forms.Application.Run
(System.Windows.Forms.ApplicationContext
) [0x00014] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.
Windows.Forms\System.Windows.Forms\Application.cs:630
at System.Windows.Forms.Application.Run (System.Windows.Forms.Form) [0x00000]
in

C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\
System.Windows.Forms\Application.cs:618
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun
(
) <0x00040>
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run
(st
ring[]) <0x0000b>
at intramem_contact_lookup.My.MyApplication.Main (string[]) <0x0003e>

The exe crashes with the following error message every time it is run.  


Steps to reproduce the problem:
1. Create a vb application with two forms
2. Add a combo box to one of the forms with style=dropdownlist
3. Add some values to the combo box and add a SelectedChangeCommitted or
SelectedIndexChanged event to it
4. From this event create an instance of the other form and use the command
form.show to show the form


Actual Results:

Unhandled Exception: System.NullReferenceException: Object reference not set to
an instance of an object
at System.Windows.Forms.ComboBox.DropDownListBoxFinished () [0x00031] in
C:\cygw
in\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\System.W
indows.Forms\ComboBox.cs:1518
at (wrapper remoting-invoke-with-check)
System.Windows.Forms.ComboBox.DropDownLi
stBoxFinished () <0x00038>
at ComboListBox.HideWindow () [0x0001e] in
C:\cygwin\tmp\monobuild\build\BUILD\m
ono-1.2.6\mcs\class\Managed.Windows.Forms\System.Windows.Forms\ComboBox.cs:2252
at ComboListBox.OnMouseUp (System.Windows.Forms.MouseEventArgs) [0x0006a] in
C:\
cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Syst
em.Windows.Forms\ComboBox.cs:2350
at System.Windows.Forms.Control.WmLButtonUp (System.Windows.Forms.Message&)
[0x0
005c] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Window
s.Forms\System.Windows.Forms\Control.cs:5253
at System.Windows.Forms.Control.WndProc (System.Windows.Forms.Message&)
[0x0017c
] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Fo
rms\System.Windows.Forms\Control.cs:5006
at ComboListBox.WndProc (System.Windows.Forms.Message&) [0x0002a] in
C:\cygwin\t
mp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\System.Windo
ws.Forms\ComboBox.cs:2419
at ControlWindowTarget.OnMessage (System.Windows.Forms.Message&) [0x00000] in
C:
\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Sys
tem.Windows.Forms\Control.cs:225
at ControlNativeWindow.WndProc (System.Windows.Forms.Message&) [0x00000] in
C:\c
ygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\Syste
m.Windows.Forms\Control.cs:206
at System.Windows.Forms.NativeWindow.WndProc
(intptr,System.Windows.Forms.Msg,in
tptr,intptr) [0x0006a] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\cla
ss\Managed.Windows.Forms\System.Windows.Forms\NativeWindow.cs:188
at System.Windows.Forms.XplatUIWin32.InternalWndProc
(intptr,System.Windows.Form
s.Msg,intptr,intptr) [0x0002c] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6
\mcs\class\Managed.Windows.Forms\System.Windows.Forms\XplatUIWin32.cs:1886
at (wrapper native-to-managed)
System.Windows.Forms.XplatUIWin32.InternalWndProc
 (intptr,System.Windows.Forms.Msg,intptr,intptr) <0x00065>
at (wrapper managed-to-native)
System.Windows.Forms.XplatUIWin32.Win32DispatchMe
ssage (System.Windows.Forms.MSG&) <0x00004>
at System.Windows.Forms.XplatUIWin32.DispatchMessage
(System.Windows.Forms.MSG&)
 [0x00000] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.W
indows.Forms\System.Windows.Forms\XplatUIWin32.cs:2081
at System.Windows.Forms.XplatUI.DispatchMessage (System.Windows.Forms.MSG&)
[0x0
0000] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Window
s.Forms\System.Windows.Forms\XplatUI.cs:551
at System.Windows.Forms.Application.RunLoop
(bool,System.Windows.Forms.Applicati
onContext) [0x00359] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class
\Managed.Windows.Forms\System.Windows.Forms\Application.cs:844
at System.Windows.Forms.Application.Run
(System.Windows.Forms.ApplicationContext
) [0x00014] in
C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.
Windows.Forms\System.Windows.Forms\Application.cs:630
at System.Windows.Forms.Application.Run (System.Windows.Forms.Form) [0x00000]
in

C:\cygwin\tmp\monobuild\build\BUILD\mono-1.2.6\mcs\class\Managed.Windows.Forms\
System.Windows.Forms\Application.cs:618
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun
(
) <0x00040>
at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run
(st
ring[]) <0x0000b>
at intramem_contact_lookup.My.MyApplication.Main (string[]) <0x0003e>


Expected Results:

The form to appear and no error

How often does this happen? 

Every time


Additional Information:

This is very annoying


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