Update an integer in an ADO RecordSet in C++ - c++

Question

I am trying to update a record in an ADO RecordSet. The recordset is loaded from a XML file, that has previously been saved to disc via rs->Save.
When trying to assign an integer value, I get a _com_error Exception:
HRESULT = -2147217887
Description = Fehler bei einem aus mehreren Schritten bestehenden Vorgang. Prüfen Sie die einzelnen Statuswerte.
Message = IDispatch error #3105
Source = Microsoft Cursor Engine
The connections Error collection yields the same message and no additional details.
I cannot figure out why the assignment does not work. What would be the correct way to assign the value to the field in question?
The variant returned from the Recordset via GetValue() is of the type VT_I4.
It seems to be a conversion issue however. The field won't accept the type of variant it gets assigned. However v = _variant_t(1l, VT_I4); did not work either.
_RecordsetPtr DataService::LoadRecordsetFromXML(string fileName)
{
//get a recordset
_RecordsetPtr rs;
try {
HRESULT hr = rs.CreateInstance(__uuidof(Recordset));
if(hr)
return nullptr;
hr = rs->Open(fileName.c_str(),"Provider=MSPersist;",adOpenDynamic,adLockBatchOptimistic,adCmdFile);
if(hr)
return nullptr;
return rs;
}
catch (_com_error &ce)
{
ShowComErrorMessageBox(ce, rs);
}
catch(...)
{
AfxMessageBox("An unknown error has occured.");
}
return nullptr;
}
bool DataService::AddMemoToXML(Memo m, string fileName)
{
_RecordsetPtr rs = LoadRecordsetFromXML(fileName);
if(!rs)
{
return false;
}
std::stringstream fstream;
fstream << "MEMO_ID = " << m.OldId;
try {
rs->Filter = fstream.str().c_str();
HRESULT hr;
if(rs->adoEOF)
{
hr = rs->AddNew();
}
//set values
{
FieldPtr field;
_bstr_t bstring;
_variant_t v;
field = rs->Fields->GetItem("MEMO_ID");
v = _variant_t(m.Id);
DataTypeEnum t = field->GetType(); //adInteger
field->PutValue(v); //Exception here
field->Value = v; //Exception here
field->Value = m.Id; //Exception here
field = rs->Fields->GetItem("MEMO_TEXT");
bstring = m.Text.c_str();
field->Value = bstring; //works fine
}
rs->Update();
rs->Filter = "";
bool ret = SaveRecordsetToXML(rs, fileName);
rs->Close();
return ret;
}
catch (_com_error &ce)
{
ShowComErrorMessageBox(ce, rs);
}
catch(...)
{
AfxMessageBox("An unknown error has occured.");
}
return false;
}
*edit: The memo class for reference:
class Memo
{
public:
Memo(void);
virtual ~Memo(void);
int Id;
int OldId;
wstring Text;
int Person;
wstring Firma;
int OrgId;
int JobId;
wstring PCode;
int UserId;
int RolleId;
wstring Kat;
COleDateTime ContactDate;
wstring Knoten;
wstring CodeV;
wstring CodeR;
wstring Eint;
wstring Stichwort;
};

Answer 1

Further testing on different fields yielded that the conversion like the following works.
field = rs->Fields->GetItem("PERSON");
v = 10l;
field->Value = v;
and that v = _variant_t(1l, VT_I4); is fine, too.
The error has to be related to the properties of the field MEMO_ID and is probably raised due to the fact, that it is an AutoId column.
An integer without a cast to long might use the wrong constructor of the variant, interpreting the number as memory location.