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.NET application just closing randomly, event viewer shows P9 system.nullreferenceexception

Posted on 2008-10-19
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Last Modified: 2008-11-02
I've been having random crashes in my application lately... I can't seem to pinpoint what is going on. The application just closes.

Event Viewer shows:

EventType clr20r3, P1 y3stand.exe, P2 1.0.0.0, P3 48f82eb0, P4 system, P5 2.0.0.0, P6 471ebf0d, P7 2c3a, P8 c, P9 system.nullreferenceexception, P10 NIL.

I've added this to the main Form

    Public Event UnhandledException As UnhandledExceptionEventHandler

    Sub Main()
        Dim currentDomain As AppDomain = AppDomain.CurrentDomain
        AddHandler currentDomain.UnhandledException, AddressOf MyHandler
    End Sub

    Sub MyHandler(ByVal sender As Object, ByVal args As UnhandledExceptionEventArgs)
        Dim e As Exception = DirectCast(args.ExceptionObject, Exception)
        Debug.WriteLine("MyHandler caught : " + e.Message)
        LogError2("MyHandler caught : " + e.Message)
    End Sub


LogError2 function opens an httprequest to record the message in my database with a tiemstamp, etc.


Apparently this unhandledexception wasn't caught by this handler... did I do something wrong? How do you guys suggest I locate / handle this?


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Question by:mcainc
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Wayne Taylor (webtubbs) earned 500 total points
Comment Utility
If you are using .Net 2.0, you can use the Application events, which contains an UnhandledException event.

Go to your project properties, then in the "Application" tab, click the "View Application Events" button, then paste the below routine in the MyApplication class.

Wayne
        Private Sub MyApplication_UnhandledException(ByVal sender As Object, ByVal e As Microsoft.VisualBasic.ApplicationServices.UnhandledExceptionEventArgs) Handles Me.UnhandledException

            Debug.WriteLine("MyHandler caught : " + e.Exception.Message)

            LogError2("MyHandler caught : " + e.Exception.Message)

        End Sub

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Author Comment

by:mcainc
Comment Utility
awesome, thanks i will try this
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Author Comment

by:mcainc
Comment Utility
hmm, it still didn't catch it... the app just closed

event viewer showed this:

EventType clr20r3, P1 y3stand.exe, P2 1.0.0.0, P3 48fba928, P4 system, P5 2.0.0.0, P6 471ebf0d, P7 2c3a, P8 c, P9 system.nullreferenceexception, P10 NIL.

there is some threading in the application, would this cause it?

there is also an external control / dll that is used occasionally, i'm starting to think this might be it, what do you think?

Delcare Function EncryptGrp Lib "C:\EncGrp3.dll" .....

is there any way to catch / contain these errors?

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Author Comment

by:mcainc
Comment Utility
is there a decent free debugging software i can use to load the process & keep an eye on it?

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Expert Comment

by:Abh4IT
Comment Utility
Not able to identify when it crashes. Is it during inactivity or during some activity it crashes. If it sits idle and crashes, do you have any timer based implementation that restarts at some particular intervals. Can you be a litte more detail of what and how it is happening, so that we can help? Somewhere in your code a codepart is hit with an object coming as null. Before you operate on certain objects you should have the check if object is null. for example fileobjects..
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Author Comment

by:mcainc
Comment Utility
I do believe it is happening somewhere in a timer

I'll try to add some object checking as you suggested
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Author Comment

by:mcainc
Comment Utility
im doing some testing now after adding some checking for all of the objects

is there a reason that application events didn't catch this error though? i was under the impression that it would catch any unhanded exceptions
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