Ben Voigt wrote:
> "Amit Dedhia" <amitdedhia@yahoo.com> wrote in message
> news:1160608594.944640.298370@i3g2000cwc.googlegroups.com...
> > Hi All
> >
> > I have a VC++ 2005 MFC application with all classes defined as
> > unmanaged classes. I want to write my application data in xml format.
> > Since ADO.NET has buit in functions available for this, I want to use
> > it. Is it possible to call Managed class functions from Unmanaged
> > class? How to do it?
> >
> > I did something like this.
> > I declared a managed class (in C++ CLI) called as MyManagedClass whose
> > public interface has functions to write application data in XML format.
> > It internally uses ADO.NET classes to achieve this. This class is
> > declared in a seperate dll compiled with '\clr' option.
> >
> > Now I created an unmanaged wrapper class which wraps the managed class
> > (defined in the same dll as that of managed class). The unmanaged
> > wrapper, call it as MyUnmanagedWrapper, has a data member declared as
> >
> > gcroot<Object^> handleToManagedClass;
>
> Should be
> gcroot<MyManagedClass^> handleToManagedClass;
>
> >
> > This is declared in the top of the class. It has wrapper methods whose
> > implementation is something like this:
> >
> > void MyUnmanagedWrapper::Method1()
> > {
> > (*this)->Method1();
> Should be
> handleToManagedClass->Method1();
>
> > }
> >
> > and then I have...
> >
> > class MyApplicationClass
> > {
> > MyUnmanagedWrapperInstance.Method1();
> > }
> >
> > Everything complies well. However, when the above method is run, I get
> > Access Violation error. It does not even go inside the method.
> >
> > Can anyone tell why there is access violation?
> Where is handleToManagedClass initialized? Initially it will hold a
> nullptr. Testing a gcroot for nullptr is a pain, try:
> (handleToManagedClass.operator->() != nullptr)

>
>
> >
> > Best regards
> > Amit Dedhia
> >