How to read the buffer from the SQL's image field type ? [modified]

[wangningyu]

:) I use this way to read the binary buffers from the SQL's image field type. the m_pBuffer's value is 0xFF all the same int the Debug Mode / Watch. But I use the SQL Query Analyzer, it can be found. why is it ? the filed info: Version varchar(100) Buffer image(16) the code fragment:

BOOL CTestDlg::ReadBinary()
{
try
{
OleInitialize(NULL);
CString strTemp = _T("");
CString strDat = _T("");
CString strVer = _T("");
char *pBuf = NULL;
_bstr_t bstrsource = "select * from db_somedatease";

	m\_pRecordset.CreateInstance("ADODB.Recordset");
	m\_pRecordset->Open(bstrsource,\_variant\_t((IDispatch\*)m\_pConnection,TRUE),adOpenStatic,adLockOptimistic,adCmdText);
	m\_pRecordset->MoveFirst();
	while(VARIANT\_FALSE == m\_pRecordset->adoEOF)
	{
		HANDLE		m\_hFile	   = INVALID\_HANDLE\_VALUE;
		HANDLE		m\_hMapping = INVALID\_HANDLE\_VALUE;
		DWORD		m\_dwSize   = 0;
		char		\*m\_pSrc    = NULL;
		char		\*m\_pBuffer = NULL;
		\_variant\_t	vtVer = m\_pRecordset->GetCollect("Version");
		VARIANT		varBLOB;

		// get the file path by version field.
		strVer = VariantToCString(vtVer);
		strTemp.Format(\_T("%s\\\\Dat\\\\%s.tmp"),GetExePath(),strVer);

		// get the file size, and then use file mapping.
		m\_dwSize = m\_pRecordset->GetFields()->GetItem("Buffer")->ActualSize;
		if (m\_dwSize > 0)
		{
			m\_hFile = CreateFile(strTemp,GENERIC\_ALL,FILE\_SHARE\_READ | FILE\_SHARE\_WRITE,NULL,
				CREATE\_ALWAYS,FILE\_ATTRIBUTE\_NORMAL,NULL);
			
			if(m\_hFile == INVALID\_HANDLE\_VALUE)
			{
				CString	strError = \_T("");
				strError.Format(\_T("CreateFile Failed！Error Code: %d"),GetLastError());
				::MessageBox(NULL,strError,NULL,NULL);
				return FALSE;
			}
			
			m\_hMapping = CreateFileMapping(m\_hFile,NULL,PAGE\_READWRITE,0,m\_dwSize,NULL);
			if(m\_hMapping == NULL)
			{
				CString	strError = \_T("");
				strError.Format(\_T("CreateFileMapping Failed！Error Code: %d"),GetLastError());
				::MessageBox(NULL,strError,NULL,NULL);
				CloseHandle(m\_hFile);
				return FALSE;
			}
			
			m\_pSrc = (char \*)MapViewOfFile(m\_hMapping,FILE\_MAP\_ALL\_ACCESS,0,0,0);
			if(m\_pSrc == NULL)
			{
				CString	strError = \_T("");
				strError.Format(\_T("MapViewOfFile Failed！Error Code: %d"),GetLastError());
				::MessageBox(NULL,strError,NULL,NULL);
				CloseHandle(m\_hMapping);
				CloseHandle(m\_hFile);
			}
			memset(m\_pSrc,0xFF,m\_dwSize);
			VariantInit(&varBLOB);
			
			// get the binary file size.
			varBLOB = m\_pRecordset->GetFields()->Get