Is this a bug in Exception.Source?

microsoft.public.dotnet.framework

9 Mar 2006 11:08 PM

Kunnis

I'm running into an issue with throwing exceptions from unmanaged code using
v1.1 of the framework. My application uses the Exception EAB, which displays
the source as part of the logging. I've been refactoring my code to throw
exceptions insted of returning error codes which had an issue with being
ignored, and when I have the EAB log an exception, Exception.get_Source is
throwing a NullReferenceException.   Below is a case that will cause that
exception, just create a managed c++ console app, and paste this in for
_tmain.

#include "stdafx.h"

#using <mscorlib.dll>

using namespace System;

int _tmain()
{
    Console::WriteLine(S"Starting unmanaged Test App");
    try
    {
        throw new System::Exception("Foo");
    }
    catch( System::Exception* ex )
    {
        Console::WriteLine(S"Exception Caught, Getting ready to display the
Source:");

        //The next line throws an exception
        Console::WriteLine(ex->Source);
    }
    return 0;
}

This test app errors out with a null ref exception.

I reflected the property, the work is done in these lines:

//C# Code, from System.Exception.get_Source()
StackTrace trace1 = new StackTrace(this, true);
if (trace1.FrameCount > 0)
{
    StackFrame frame1 = trace1.GetFrame(0);
    System.Reflection.MethodBase base1 = frame1.GetMethod();
    System.Type type1 = base1.DeclaringType; //Executing this line causes an
exception to be throw.
    System.Reflection.Module mod = type1.Module;
    System.Reflection.Assembly asm = mod.Assembly;
    //string _source = asm.nGetSimpleName();
}

If I execute these lines (substituting an exception for 'this' in
StrackTrace's constructor) The exception occurs on the marked line. Now at
least I think it's because I'm throwing the exception from an unmanaged class

I read up, and I think the problem is base1.DeclaringType can return null,
but there's no checks to see if that property returned null.

from the MSDN: "If the MemberInfo object is a global member, (that is, it
was obtained from Module.GetMethods, which returns global methods on a
module), then the returned DeclaringType will be a null reference (Nothing in
Visual Basic)."

I'm planning on converting the class that throws the exception to a managed
class to avoid this exception, are there any other suggestions? Maybe before
passing the exception into the EAB, I can try to access the Source property,
and if it throws an exception, set the source to "Unmanaged Code" or
something wierd like that.

Kunnis