Access violation in MSCORWKS.DLL

[techie]

I have created an event sink in my ATL COM project. The event sink receives
events from a C# component. There is no problem with receiving events but
when my COM object is released I get an access violation - (MSCORWKS.DLL):
0xC0000005: Access Violation.

At first I thought it could be due to my C++ code but after quite a lot of
investigation I don't think there is nothing wrong with it. The access
violation occurs after the destructor of my COM object. It seems to be
coming
from the .NET garbage collector. Could it be that the GC is trying to
delete memory twice? How do I fix this problem? The events are being sent
from the TransferModule.

I'm very new to C#. Should I implment a dispose method?

Here's the code for my Transfer Module:

using System;
using System.Runtime. InteropServices ;
using ATWSConsumer.Tr ansferServer;
using System.IO;
using System.Windows. Forms;

namespace ATWSConsumer
{
public delegate void UpdateDelegate( int percentage);

[Guid("2278B7FD-3DD8-42cc-93D7-824C2FB32EA9")]
public interface ITransferModule
{
int TransferBlockSi ze {get; set;}
ConnectionModul e Connection {get; set;}

bool Discover();
}

[Guid("2E638A47-161F-4b6c-9BBC-AD4AC2EC53FA"),
InterfaceType(C omInterfaceType .InterfaceIsIDi spatch)]
public interface ITransferModule Event
{
[DispId(1)] void UpdateProgress( int percentage);
}

[Guid("40A69B6B-7F46-4929-BEA5-CFCBB45D5443"),
ClassInterface( ClassInterfaceT ype.None),
ComSourceInterf aces(typeof(ITr ansferModuleEve nt))]
public class TransferModule : ITransferModule
{
public event UpdateDelegate UpdateProgress;

public ConnectionModul e m_oConnection;
public string m_sError;
public int m_nTBSize;

public ConnectionModul e Connection
{
get{return m_oConnection;} set{m_oConnecti on = value;}
}

public string GetLastError()
{
return m_sError;
}

public int TransferBlockSi ze
{
get {return m_nTBSize;} set {m_nTBSize = value;}
}

private TransferService GetTransferServ ice()
{
if ( m_oConnection == null || m_oConnection.m _serviceCache == null )
return null;
ServiceInfo si = m_oConnection.m _serviceCache.G etServiceByType
(ServiceInfo.Se rviceType.Trans ferService);

if (si == null)
{
m_oConnection.S etErrorString
(m_oConnection. m_serviceCache. GetLastError()) ;
return null;
}

TransferService transferService = new TransferService ();
transferService .Credentials =
System.Net.Cred entialCache.Def aultCredentials ; // to resolve security
problems with ASP by Yuriy E. Zatuchnyy at 23 Sep 2004
transferService .Url = si.m_sServiceAd dress;

return transferService ;
}

public TransferModule( )
{
// default transfer block size (4k)
m_nTBSize = 4096;
}

public TransferModule( ConnectionModul e connectionModul e)
{
m_oConnection = connectionModul e;
// default transfer block size (4k)
m_nTBSize = 4096;
}

public bool Discover()
{
TransferService transferService = GetTransferServ ice();
if (transferServic e == null)
return false;

return true;
}

public string UploadFile(stri ng sFilePath)
{
int nBytesRead = 0;
byte[] byteBuffer;
string sUploadToken = "";
FileStream fileStream = null;
long lTotalBytesRead = 0;

TransferService transferService = GetTransferServ ice();
if (transferServic e==null)
return "";

// get the upload token to allow an upload
WSResult wsResult = transferService .RequestUploadT oken
(/*m_oConnection. m_strSessionKey ,*/0); // by Yuriy E. Zatuchnyy at 28 July
2004
if (!wsResult.Succ ess)
{
m_sError = wsResult.Descri ption.InnerText ;
return "";
}

sUploadToken = wsResult.Descri ption.InnerText ;

try
{
fileStream = new FileStream (sFilePath, FileMode.Open,
FileAccess.Read , FileShare.ReadW rite);
}
catch (Exception E)
{
m_sError = E.Message;
CleanupUpload(s UploadToken);
return "";
}

long lFileSize = fileStream.Leng th;
byteBuffer = new byte[m_nTBSize];
nBytesRead = fileStream.Read (byteBuffer,0,m _nTBSize);
while (nBytesRead > 0)
{
wsResult = transferService .Upload
(sUploadToken,n BytesRead,byteB uffer);
if (!wsResult.Succ ess)
{
m_sError = wsResult.Descri ption.InnerText ;
fileStream.Clos e ();
CleanupUpload(s UploadToken);

return "";
}
lTotalBytesRead += nBytesRead;
if (UpdateProgress !=null)
{
UpdateProgress( (int)((lTotalBy tesRead * 100) / lFileSize));
}
nBytesRead = fileStream.Read (byteBuffer,0,m _nTBSize);
}

fileStream.Clos e ();
return sUploadToken;
}

public bool CleanupUpload(s tring sToken)
{
TransferService transferService = GetTransferServ ice();
if (transferServic e == null)
return false;

WSResult wsResult = transferService .UploadComplete (sToken);

if (!wsResult.Succ ess)
{
m_sError = wsResult.Descri ption.InnerText ;
return false;
}

return true;
}

public bool DownloadFile(st ring sFileLocation, string sToken, long
lFileSize)
{
long lChunkNumber = 0;
long lBytesReceived = 0;
FileStream fileStream = null;
TransferService transferService = GetTransferServ ice();
if (transferServic e == null)
return false;

try
{
fileStream = new FileStream (sFileLocation, FileMode.Create );
}
catch (Exception E)
{
m_sError = E.Message;
return false;
}

TransferServer. BinaryResult binResult =
transferService .Download(sToke n, lChunkNumber++, m_nTBSize);
while (binResult.lByt esRead > 0)
{
if (!binResult.Suc cess)
{
m_sError = binResult.Descr iption.InnerTex t;
fileStream.Clos e ();
return false;
}
lBytesReceived += binResult.lByte sRead;
if (UpdateProgress !=null)
{
UpdateProgress( (int)((lBytesRe ceived * 100) / lFileSize));
}
fileStream.Writ e (binResult.Cont ent,0,(int)binR esult.lBytesRea d);
binResult = transferService .Download(sToke n, lChunkNumber++,
m_nTBSize);
}

fileStream.Clos e ();

return true;
}
}
}