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NullReferenceException in Row.Reindex()

 
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MHB



Joined: 04 Apr 2005
Posts: 69

PostPosted: Wed Nov 02, 2005 4:03 pm    Post subject: NullReferenceException in Row.Reindex() Reply with quote

A user got this error, supposedly while trying to adjust the width of a column by dragging the divider, but it looks like he clicked the header instead... This could have something to do with a synchronization problem in my child list code, but even if it has, it shouldn't result in an exception, right?

Code:

System.NullReferenceException: Object reference not set to an instance of an object.
   at Infralution.Controls.VirtualTree.Row.Reindex(Int32 index)
   at Infralution.Controls.VirtualTree.Row.set_Expanded(Boolean value)
   at Infralution.Controls.VirtualTree.Row.EnsureVisible()
   at Infralution.Controls.VirtualTree.VirtualTree.OnSortColumnChanged()
   at OntoEdit.OntoTree.OnSortColumnChanged()
   at Infralution.Controls.VirtualTree.VirtualTree.set_SortColumn(Column value)
   at Infralution.Controls.VirtualTree.ColumnHeaderWidget.OnClick(EventArgs e)
   at Infralution.Controls.WidgetControl.OnClick(EventArgs e)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at Infralution.Controls.BorderedControl.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)


Btw, isn't the "drag-able" area around a column divider rather small and hard to hit? I just noticed that it only extends to the left of the divider... At least in explorer the area is larger and extends to both sides.
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Infralution



Joined: 28 Feb 2005
Posts: 5027

PostPosted: Wed Nov 02, 2005 11:04 pm    Post subject: Reply with quote

You're right you shouldn't get a null reference exception from virtual tree - even if there is a problem with your code. I've taken a look at the code in question - the only possible way a null reference exception could be generated (that I could see) would be if the SelectedRow had somehow been deleted when the data was sorted. If you could replicate the problem and provide a sample that would greatly assist in tracking down the source of the problem.
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MHB



Joined: 04 Apr 2005
Posts: 69

PostPosted: Thu Nov 03, 2005 12:00 am    Post subject: Reply with quote

Sorry, but I haven't been able to replicate the problem myself, so I don't think I can help any further. Of course I can encourage the user who got the error to try hard to make the error to reappear Smile His computer is rather slow, maybe that could have something to do with it (I'm thinking along the lines of a race condition that might depend on user interaction, gui redraw or something like that...).
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