Recordsets: converting COleVariant

Hello,

VC++6.0 Prof, Win98

I am a new VC++ programmer looking for help.

I am trying to open a recordset on the fly and read a value from the first record. This apparently
necessitates using GetFieldValue with a COleVariant variable. My code is as follows:-

CDaoDatabase* pDB = new CDaoDatabase;
try
{
pDB->Open("D:\\Vb4&5prg\\Experiment\\Mail1.mdb");
}
catch(CDaoException* e)
{
AfxMessageBox(e->m_pErrorInfo->m_strDescription, MB_ICONEXCLAMATION);
e->Delete();
}

CDaoRecordset pRS(pDB);
CString mText = "Select * from Folders";
try
{
pRS.Open(AFX_DAO_USE_DEFAULT_TYPE, mText,0);
}
catch(CDaoException* e)
{
AfxMessageBox(e->m_pErrorInfo->m_strDescription, MB_ICONEXCLAMATION);
e->Delete();
}
pRS.MoveFirst();
COleVariant mVar;
int i = 1;
mVar = pRS.GetFieldValue(i);
mText = mVar;
AfxMessageBox(mText);
pDB->Close();
delete pDB;



The above fails on the attempt to pass the COleVariant value into a CString. I would be grateful for code
examples on how to convert a COleVariant into something that can be readily used, preferably a CString.
If there are any other errors in my code, I'd also be glad to know.

Hoping for help from all you experts,

TrimTrom

----------------------------------
Email: [email protected]
Surrey, England
----------------------------------

I have never done anything like you are doing, but to get a COleVariant into a CString, assuming that it has a valid BSTR in it, all you need to do is:

CString MyString = MyOleVariant.bstrVal;

--michael

You will need a function, that is not defined in MFC to convert COleVariant to CString.
This function is defined in the follow lines:

//This function is necessary to strVARIANT work
LPCTSTR strBOOL(BOOL bFlag)
{
return bFlag ? _T("TRUE") : _T("FALSE");
}


//You must insert the prototype in the headers
CString strVARIANT(const COleVariant& var)
{
CString strRet;
strRet = _T("Fish");
switch(var.vt){
case VT_EMPTY:
case VT_NULL:
strRet = _T("NULL");
break;
case VT_I2:
strRet.Format(_T("%hd"),V_I2(&var));
break;
case VT_I4:
strRet.Format(_T("%d"),V_I4(&var));
break;
case VT_R4:
strRet.Format(_T("%e"),(double)V_R4(&var));
break;
case VT_R8:
strRet.Format(_T("%e"),V_R8(&var));
break;
case VT_CY:
strRet = COleCurrency(var).Format();
break;
case VT_DATE:
strRet = COleDateTime(var).Format(_T("%m %d %y"));
break;
case VT_BSTR:
strRet = V_BSTRT(&var);
break;
case VT_DISPATCH:
strRet = _T("VT_DISPATCH");
break;
case VT_ERROR:
strRet = _T("VT_ERROR");
break;
case VT_BOOL:
return strBOOL(V_BOOL(&var));
case VT_VARIANT:
strRet = _T("VT_VARIANT");
break;
case VT_UNKNOWN:
strRet = _T("VT_UNKNOWN");
break;
case VT_I1:
strRet = _T("VT_I1");
break;
case VT_UI1:
strRet.Format(_T("0x%02hX"),(unsigned short)V_UI1(&var));
break;
case VT_UI2:
strRet = _T("VT_UI2");
break;
case VT_UI4:
strRet = _T("VT_UI4");
break;
case VT_I8:
strRet = _T("VT_I8");
break;
case VT_UI8:
strRet = _T("VT_UI8");
break;
case VT_INT:
strRet = _T("VT_INT");
break;
case VT_UINT:
strRet = _T("VT_UINT");
break;
case VT_VOID:
strRet = _T("VT_VOID");
break;
case VT_HRESULT:
strRet = _T("VT_HRESULT");
break;
case VT_PTR:
strRet = _T("VT_PTR");
break;
case VT_SAFEARRAY:
strRet = _T("VT_SAFEARRAY");
break;
case VT_CARRAY:
strRet = _T("VT_CARRAY");
break;
case VT_USERDEFINED:
strRet = _T("VT_USERDEFINED");
break;
case VT_LPSTR:
strRet = _T("VT_LPSTR");
break;
case VT_LPWSTR:
strRet = _T("VT_LPWSTR");
break;
case VT_FILETIME:
strRet = _T("VT_FILETIME");
break;
case VT_BLOB:
strRet = _T("VT_BLOB");
break;
case VT_STREAM:
strRet = _T("VT_STREAM");
break;
case VT_STORAGE:
strRet = _T("VT_STORAGE");
break;
case VT_STREAMED_OBJECT:
strRet = _T("VT_STREAMED_OBJECT");
break;
case VT_STORED_OBJECT:
strRet = _T("VT_STORED_OBJECT");
break;
case VT_BLOB_OBJECT:
strRet = _T("VT_BLOB_OBJECT");
break;
case VT_CF:
strRet = _T("VT_CF");
break;
case VT_CLSID:
strRet = _T("VT_CLSID");
break;
}
WORD vt = var.vt;
if(vt & VT_ARRAY){
vt = vt & ~VT_ARRAY;
strRet = _T("Array of ");
}
if(vt & VT_BYREF){
vt = vt & ~VT_BYREF;
strRet += _T("Pointer to ");
}
if(vt != var.vt){
switch(vt){
case VT_EMPTY:
strRet += _T("VT_EMPTY");
break;
case VT_NULL:
strRet += _T("VT_NULL");
break;
case VT_I2:
strRet += _T("VT_I2");
break;
case VT_I4:
strRet += _T("VT_I4");
break;
case VT_R4:
strRet += _T("VT_R4");
break;
case VT_R8:
strRet += _T("VT_R8");
break;
case VT_CY:
strRet += _T("VT_CY");
break;
case VT_DATE:
strRet += _T("VT_DATE");
break;
case VT_BSTR:
strRet += _T("VT_BSTR");
break;
case VT_DISPATCH:
strRet += _T("VT_DISPATCH");
break;
case VT_ERROR:
strRet += _T("VT_ERROR");
break;
case VT_BOOL:
strRet += _T("VT_BOOL");
break;
case VT_VARIANT:
strRet += _T("VT_VARIANT");
break;
case VT_UNKNOWN:
strRet += _T("VT_UNKNOWN");
break;
case VT_I1:
strRet += _T("VT_I1");
break;
case VT_UI1:
strRet += _T("VT_UI1");
break;
case VT_UI2:
strRet += _T("VT_UI2");
break;
case VT_UI4:
strRet += _T("VT_UI4");
break;
case VT_I8:
strRet += _T("VT_I8");
break;
case VT_UI8:
strRet += _T("VT_UI8");
break;
case VT_INT:
strRet += _T("VT_INT");
break;
case VT_UINT:
strRet += _T("VT_UINT");
break;
case VT_VOID:
strRet += _T("VT_VOID");
break;
case VT_HRESULT:
strRet += _T("VT_HRESULT");
break;
case VT_PTR:
strRet += _T("VT_PTR");
break;
case VT_SAFEARRAY:
strRet += _T("VT_SAFEARRAY");
break;
case VT_CARRAY:
strRet += _T("VT_CARRAY");
break;
case VT_USERDEFINED:
strRet += _T("VT_USERDEFINED");
break;
case VT_LPSTR:
strRet += _T("VT_LPSTR");
break;
case VT_LPWSTR:
strRet += _T("VT_LPWSTR");
break;
case VT_FILETIME:
strRet += _T("VT_FILETIME");
break;
case VT_BLOB:
strRet += _T("VT_BLOB");
break;
case VT_STREAM:
strRet += _T("VT_STREAM");
break;
case VT_STORAGE:
strRet += _T("VT_STORAGE");
break;
case VT_STREAMED_OBJECT:
strRet += _T("VT_STREAMED_OBJECT");
break;
case VT_STORED_OBJECT:
strRet += _T("VT_STORED_OBJECT");
break;
case VT_BLOB_OBJECT:
strRet += _T("VT_BLOB_OBJECT");
break;
case VT_CF:
strRet += _T("VT_CF");
break;
case VT_CLSID:
strRet += _T("VT_CLSID");
break;
}
}
return strRet;
}


Example:

CString varstring;
COleVariant varole;
varole = tb.GetFieldValue("Field_Name");
varstring = strVARIANT(varole);

Brilliant - it seems to be a very comprehensive function!

Thanks,

TrimTrom

----------------------------------
Email: [email protected]
Surrey, England
----------------------------------

I noticed your post this last Tues, but didn't get a chance to respond. The sample code on your post doesn't include "endcatch" to both "try/catch" exception traps. I made this mistake once, and got an error. Check your actual code and see if you omitted "endcatch".

This method only works some of the time for me (don't really know why), but I've never had a problem with using the V_BSTRT macro:CString MyString=V_BSTRT(&MyOleVariant);