How to obtain unmanaged stack information from a managed block of code in Microsoft Visual Studio .NET (841888)

MORE INFORMATION

There is no intrinsic way to step through a stack of unmanaged code from a block of managed code. If you are working with managed code, and you want to step through the stack of unmanaged code, you must use Platform Invocation Services (PInvoke) to call the GetExceptionInformation function and the StackWalk64 function of the Win32 API.

If you receive an exception from your unmanaged code, you must leave the managed code block through your Filter function that is used for exception handling. The Win32 API GetExceptionInformation function is valid only in the Filter function. You can only step through the stack in the Filter function. When execution reaches the Handler function, the exception is complete, and any stack information that executes before the exception is now invalid.

Programmers of managed languages frequently hide the Filter function and instead use multiple Catch clauses. To obtain valid stack information, you must use the Filter function. If you step through the unmanaged stack outside the Filter function, you will receive unpredictable and frequently hazardous results.

The following code samples show you where to step through a stack of unmanaged code from a block of managed code:

//----------------C++  code------------------//
__try
  Code();
__except(Filter())
  Handler();

int Filter()
{
    // Inside the Filter() statement.  PInvoke to Win32 DbgHelp APIs here to stackwalk.
    return 1;  // returning -1 or 0 will cause Filter() to fail, Handler() is not executed and the next outer exception block will be used.
}

'//--------------VB .NET code-------------------//
Module Module1

    Sub Main()
        Try
           Throw New System.NullReferenceException()
        Catch When Filter()                                                           
           System.Console.WriteLine("Caught exception")
        End Try
    End Sub

    Function Filter() as boolean
        ' Inside Filter().   PInvoke to Win32 DbgHelp APIs here to stackwalk.
        return True      ' If you return False from Filter(), Catch() does not execute and the next outer Try/Catch block will be used.
    End Function

End Module

You cannot create a Filter function with the C# language.