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.NET Forum / .NET Framework / CLR / February 2004NullReferenceException Message Feature Request
I'm guessing that NullReferenceExceptions are by far the most common exceptions thrown in .net. Why not add the type of the reference to the message? Have it say something like: Object reference of type 'string' not set to an instance of an object. This would really help when trying to figure out where the null reference is happening. I've just spent the last two days finding a null reference that happens very intermittently. Having the type would have saved me many hours. In addition to just the type, you might be able to use reflection to give a property name or variable name. Bryan Livingston Alphora.com Please tell me you have exceptions set to 'break' in the debugger.... if you do, it's usually absolutely obvious what the null reference should have been. > I'm guessing that NullReferenceExceptions are by far the most common exceptions thrown in .net. > [quoted text clipped - 9 lines] > Bryan Livingston > Alphora.com And if not Bryan, then don't worry - you know to now :-) > Please tell me you have exceptions set to 'break' in the debugger.... if you > do, it's usually absolutely obvious what the null reference should have [quoted text clipped - 18 lines] > > Bryan Livingston > > Alphora.com Cheeky... they're off by default which seems odd to me. The options are under Debug -> Exceptions, and I usually have all set to break (with a few exceptions). I think the exception already does have the stack trace in it, so even if you're not running under the debugger you could log the stack trace of an exception which reaches a certain level. > And if not Bryan, then don't worry - you know to now :-) > [quoted text clipped - 23 lines] > > > Bryan Livingston > > > Alphora.com The exception only happens on a production website and only occours about once every three days. I havn't been able to reproduce it in a debug environment. Since we are doing financial transactions on the site I don't exactly have time to dick around with attaching a debugger. I have to get the site back up right away. Bryan ----- Stu Smith wrote: ----- Please tell me you have exceptions set to 'break' in the debugger.... if you do, it's usually absolutely obvious what the null reference should have been. "Bryan Livingston" <anonymous@discussions.microsoft.com> wrote in message news:6FDA50BD-7BF4-43C6-AD92-6DE18207002C@microsoft.com... > I'm guessing that NullReferenceExceptions are by far the most common exceptions thrown in .net. >> Why not add the type of the reference to the message? Have it say something like: > Object reference of type 'string' not set to an instance of an object. >> This would really help when trying to figure out where the null reference is happening. >> I've just spent the last two days finding a null reference that happens very intermittently. Having the type would have saved me many hours. >> In addition to just the type, you might be able to use reflection to give a property name or variable name. >> Bryan Livingston > Alphora.com For the record, here is what one of the program managers for the CLR had to say about it The NullReferenceException occurs because an instruction like “call [eax+44]” or “mov edx, [esi+24]” has resulted in an access violation. We don’t retain nearly enough information to form a correspondence between a particular register being NULL at a particular EIP and the fact that a particular reference in the application was null. Especially since the EIP might be in a shared helper like a write barrier routine or an array helper. In those cases, we would have to perform a limited stack walk to get the effective EIP The machinery that would be required to improve this error message is huge. For the foreseeable future, you will have to rely on debuggers, or on FX code explicitly checking and throwing an appropriate NullArgumentException Chris. http://blogs.msdn.com/cbrumme ----- Bryan Livingston wrote: ---- I'm guessing that NullReferenceExceptions are by far the most common exceptions thrown in .net Why not add the type of the reference to the message? Have it say something like Object reference of type 'string' not set to an instance of an object This would really help when trying to figure out where the null reference is happening I've just spent the last two days finding a null reference that happens very intermittently. Having the type would have saved me many hours In addition to just the type, you might be able to use reflection to give a property name or variable name Bryan Livingsto Alphora.com Thanks for your suggestion. I will add this to our list for future considerations. Once suggestion is create a trace/log system where you can log activities on the web site to help debug the problem. Thanks, Kelvin This posting is provided "AS IS" with no warranties, and confers no rights. -------------------- >Thread-Topic: NullReferenceException Message Feature Request >thread-index: AcP4rnQ2fwitLh6SR/CMAirGLsHYkQ== >X-Tomcat-NG: microsoft.public.dotnet.framework.clr >From: "=?Utf-8?B?QnJ5YW4gTGl2aW5nc3Rvbg==?=" <anonymous@discussions.microsoft.com> >References: <6FDA50BD-7BF4-43C6-AD92-6DE18207002C@microsoft.com> >Subject: RE: NullReferenceException Message Feature Request [quoted text clipped - 17 lines] > >For the record, here is what one of the program managers for the CLR had to say about it: The NullReferenceException occurs because an instruction like ???call [eax+44]??? or ???mov edx, [esi+24]??? has resulted in an access violation. We don???t retain nearly enough information to form a correspondence between a particular register being NULL at a particular EIP and the fact that a particular reference in the application was null. Especially since the EIP might be in a shared helper like a write barrier routine or an array helper. In those cases, we would have to perform a limited stack walk to get the effective EIP. The machinery that would be required to improve this error message is huge. For the foreseeable future, you will have to rely on debuggers, or on FX code explicitly checking and throwing an appropriate NullArgumentException. Chris. http://blogs.msdn.com/cbrumme ----- Bryan Livingston wrote: ----- I'm guessing that NullReferenceExceptions are by far the most common exceptions thrown in .net. Why not add the type of the reference to the message? Have it say something like: Object reference of type 'string' not set to an instance of an object. This would really help when trying to figure out where the null reference is happening. I've just spent the last two days finding a null reference that happens very intermittently. Having the type would have saved me many hours. In addition to just the type, you might be able to use reflection to give a property name or variable name. Bryan Livingston Alphora.com
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