I need to know how to properly marshal the data from my legacy app to
a /Net component. My legacy app uses the following IDL interface
definition:

interface IMyInterface2 : IUnknown
{
 HRESULT doit( [in, size_is(msgLength)]UCHAR* msg, [in] ULONG
msgLength );
};

When my legacy COM Client calls my .Net component that implements this
interface, an access violation (0xC0000005) exception is thrown. I've
tried everything and can not figure out why the exception is thrown in
the
COM Client.

Here is the COM Client:

#include "stdafx.h"
#include "IMyInterface2_h.h"
#include "IMyInterface2_i.c"

int _tmain(int argc, _TCHAR* argv[])
{
HRESULT hr = S_OK;
hr = ::CoInitialize( NULL );
CLSID rcid = { 0x5F850215, 0x7AC2, 0x48b8, { 0xA8, 0xCF, 0xA0, 0x08,
0xF7, 0x33, 0xD6, 0x61 } };

{
CComPtr<IMyInterface2> iMyInterface2;
hr = iMyInterface2.CoCreateInstance( rcid, NULL, CLSCTX_INPROC_SERVER
);
UCHAR* pBytes = (UCHAR*)::CoTaskMemAlloc( 20 );
::ZeroMemory( pBytes, 20 );
iMyInterface2->doit( pBytes, 20 );
}
::CoUninitialize();

return 0;
}

The exception is thrown on the statement:
iMyInterface2->doit( pBytes, 20 );
The call never gets to the .Net component's method

And here is the .Net service component. The .Net component must be
copied in the same directory as the COM client.

using System;
using System.Runtime.InteropServices;

namespace ComSrv
{
 [GuidAttribute("5F850215-7AC2-48b8-A8CF-A008F733D661")]
 public class MyClass : IMyInterface2
 {
  public void doit( byte[] msg, ulong msgLength )
  {
  }
 }

 [ComImport]
 [GuidAttribute("B55AFAEB-BC7D-4ca9-8065-F9A45FE378B6")]
 [InterfaceTypeAttribute 
ComInterfaceType.InterfaceIsIUnknown)]
 public interface IMyInterface2
 {
  void doit(
   [In, MarshalAs( UnmanagedType.LPArray, 
SizeParamIndex=1, ArraySubType=UnmanagedType.U1 )]byte[] 
msg, [In]ulong msgLength );
 }
}

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Request for Question Clarification by studboy-ga on 18 Jun 2002 12:29 PDT

I am assuming you did perform the perform the following three steps 
on the .NET component/assemby before you made the call--am I correct?

tlbexp ...

regasm ...

gacutil ...

---

Clarification of Question by clearly-ga on 18 Jun 2002 14:08 PDT

tlbexp:no
Regasm:yes
GAC:no

As the message states, I don't need to put it in the GAC because I put
the .Net component in the same directory. The component loads fine:
the CoCreateInstance call returns S_OK. In fact, I can call other
methods with different IDL signatures. The problem I am having is
specifically with a method that uses LPArray.

---

Clarification of Question by clearly-ga on 18 Jun 2002 14:15 PDT

Let me clarify that $100 is the max "Google Answers" will allow. I
would be happy to pay $400 to the first person who has a satisfactory
solution that will work with my legacy application.

---

Clarification of Question by clearly-ga on 19 Jun 2002 19:43 PDT

The question has been answered by someone else outside of Google
Answers. At this point, I will not award the List Price to anyone.

Can you please post the solution so we know.  I'm curious as to if the
msgLength argument on the doit method (a c++ ULONG) should have ben
marshaled as a uint(System.UInt32) instead of a ulong (System.Int64).