connecting MS Access through VC++ - visual-c++

Question

I am new to VC++, I am trying to write a program(after lots of googling) which connects to ms access, but its showing connection error. What am I missing or doing something wrong.
Error: [Microsoft][ODBC Driver Manager] Invalid String or Buffer Length.
Here is what I am tring
Clearn_dbView::Clearn_dbView()
: COleDBRecordView(Clearn_dbView::IDD)
{
setUpODBC();
}
Clearn_dbView::~Clearn_dbView()
{
if(hDbConn != SQL_NULL_HANDLE)
{
// Free Connection.
SQLFreeHandle(SQL_HANDLE_DBC,hDbConn);
}
if(hOdbcEnv != SQL_NULL_HANDLE)
{
SQLFreeHandle(SQL_HANDLE_ENV, hOdbcEnv);
}
}
void Clearn_dbView::setUpODBC()
{
SQLRETURN sr; //Return call for ODBC
//Allocate Environment.
sr = SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&hOdbcEnv);
if( sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO)
AfxMessageBox(_T("Error in Allocating Environment."));
// Set the App's ODBC Version
sr = SQLSetEnvAttr(hOdbcEnv,SQL_ATTR_ODBC_VERSION,(SQLPOINTER)SQL_OV_ODBC3, SQL_IS_INTEGER);
if(sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO)
AfxMessageBox(_T("Error in Setting ODBC Version."));;
// Allocate Connection
sr = SQLAllocHandle(SQL_HANDLE_DBC, hOdbcEnv, &hDbConn);
//sr = SQLAllocConnect(hOdbcEnv, &hDbConn);
if(sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO)
AfxMessageBox(_T("Error in Allocating Connection."));;
// Set Connect Timeout
sr = SQLSetConnectAttr(hDbConn, SQL_ATTR_LOGIN_TIMEOUT, (void*)5, 0);
if(sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO)
AfxMessageBox(_T("Error in Setting Login Timeout."));
}
void Clearn_dbView::displayODBCError(SQLRETURN sr, char *inMessage)
{
if(sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO) {
SQLWCHAR SqlState[6];
SQLINTEGER NativeError;
SQLWCHAR ErrMsg[SQL_MAX_MESSAGE_LENGTH];
int i = 1;
char message[1000];
strcpy (message, "");
if (inMessage) {
strcpy(message, inMessage);
strcat(message, " — ");
}
sprintf(message, "%sError in SQLConnect(): %d.",message, sr);
MessageBoxA(NULL,message,"Error",MB_OK);
while(SQLGetDiagRec(SQL_HANDLE_DBC, hDbConn, i,SqlState, &NativeError,ErrMsg, sizeof(ErrMsg), NULL)
!= SQL_NO_DATA) {
sprintf(message,"Diag: %d, SQLSTATE: %s NativeError: %d ErrMsg: %s",i++, SqlState, NativeError, ErrMsg);
MessageBoxA(NULL,message,"Error",MB_OK);
}
}
}
void Clearn_dbView::connectwithdb()
{
SQLRETURN sr;
SQLCHAR szDSN[] = "DRIVER={Microsoft Access Driver (*.mdb, *.accdb)};DSN=D:\\Avi\\P\\mydb.mdb.dsn";
SQLCHAR szUID[] = "";
SQLCHAR szAuthStr[] = "";
if(hDbConn == NULL) {
MessageBox(_T("hDbConn IS NULL"));
return;
}
sr = SQLConnectA(hDbConn, (UCHAR *)szDSN, SQL_NTS,
(UCHAR *)szUID, SQL_NTS,
(UCHAR *) szAuthStr, SQL_NTS);
if(sr != SQL_SUCCESS && sr != SQL_SUCCESS_WITH_INFO)
{
displayODBCError(sr, "Error in OnViewConnectwithsqlconnect");
}
else
{
MessageBox(_T("else executed"));
MessageBox(_T("Connected OK"));
}
}
void Clearn_dbView::OnBnClickedConnect()
{
connectwithdb();
}

Answer 1

It appears that the DSN being specified in the following line is not valid:
SQLCHAR szDSN[] = "D:\\Avi\\P\\mydb.mdb";
Based on the string "D:\\Avi\\P\\mydb.mdb", it looks like the database file and path are being specified instead of the DSN.
You will need to be sure to create an ODBC DSN using the ODBC Administrator. You will provide a string for the Data Source Name field of the configuration. That string is what you will need to specify in your code for SQLCHAR szDSN[] = "".
Here is a link that explains the error in more general details, however; if you follow what is mentioned above, that should resolve the error.