Null pointers for comboboxes when exiting application

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I'm getting nullpointerexceptions when I call Application.Exit in C#. The combobox selected index is set to null, but this sets off a series of errors when SelectedIndex_changed() is called during the exit. :sigh: I also get errors when the "SelectedIndex = -1" statement is called--again nullPointerExceptions in SelectedIndex_changed(). How should I handle this? Thanks in advance.

Posted 15-Sep-10 8:00am

envprogrammer

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Sandeep Mewara 15-Sep-10 14:15pm

Update from OP: I'm not setting it to null. When dispose() inside Application.Exit) is called, C# throws a null pointer exception.

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William Winner · Accepted Answer · 2010-09-15T08:07:00

Solution 1

First of all, how in the world are you setting ComboBox.SelectedIndex to null?

It is an int variable which is a non-nullable type.

If you're setting it to null, then that's your problem.

And if you're setting it to -1 and then getting an error in your SelectedIndex_Changed event, then you need to first check to see if SelectedIndex = -1 and exit the method.

Posted 15-Sep-10 8:07am

William Winner

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envprogrammer 15-Sep-10 14:51pm

Reason for my vote of 5
Automatic vote of 5 for accepting answer.

Marc A. Brown · Accepted Answer · 2010-09-15T08:09:00

Solution 2

Check the value of SelectedIndex and skip over the code that errors if it's null or -1.

Posted 15-Sep-10 8:09am

Marc A. Brown

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envprogrammer 15-Sep-10 14:51pm

Reason for my vote of 5
Automatic vote of 5 for accepting answer.

Marc A. Brown · Accepted Answer · 2010-09-15T08:13:00

Solution 4

Alternatively, create a form level boolean to indicate that the form is closing and set it to true in the form's closing event. Then only run the code in your combo box's changed event handler if that variable is false.

Posted 15-Sep-10 8:13am

Marc A. Brown

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envprogrammer 15-Sep-10 14:51pm

This is what I used and it appears to be the answer.

envprogrammer 15-Sep-10 14:51pm

Reason for my vote of 5
Automatic vote of 5 for accepting answer.

Marc A. Brown 15-Sep-10 14:58pm

Glad I could help.