Using ODBC Connection Pooling with CDatabase (under MFC)

Environment: Visual C++ 6

Note that in order for this to work correctly (the way I did it), you are going to have to derive a class from CDatabase, and override the OpenEx(...) method. More details on this follow...

Brief Overview

The Good News

How to do it

// 
//   m_shSQLEnv Is A SQLHANDLE Member That Must Be Freed When Your
//   Application Terminated
// 
SQLRETURN srRetCode = 0;
srRetCode = SQLSetEnvAttr( NULL, SQL_ATTR_CONNECTION_POOLING, 
        (SQLPOINTER)SQL_CP_ONE_PER_DRIVER, 0 );                  // Enable Connection Pooling
srRetCode = SQLAllocHandle( SQL_HANDLE_ENV, NULL, &m_shSQLEnv ); // Get Global Handle
Later on, I free the m_shSQLEnv handle in my CWinApp::ExitInstance() function:

if( m_shSQLEnv )                                                 // If Environment Handle For Connection Pooling Obtained
{
    SQLFreeHandle( SQL_HANDLE_ENV, m_shSQLEnv );                 // Free It
}

The Bad News

My solution to this problem was to derive a class from CDatabase, and overide the OpenEx(...) method, which Open(...) calls, to always add in the CDatabase::noOdbcDialog flag. That solved my problem. You can download the code for the CDatabase-derived class that I used. It is very simple.

Now that you have all this information, here are the steps required to use it:

• Create (or download) the CDatabase-derived class, and add it to your Project
• Create a member of the CDatabase-derived class in your CWinApp-derived (Application) class
• Create a SQLHANDLE data member in your Application class for the Enviroment Handle
• Add an accessor function that returns the address of the CDatabase-derived member you added in the previous step
• Make the necessary SQLSetEnvAttr(...) and SQLAllocHandle(...) calls as specified above
• Initially open your CDatabase-derived object (if you are using SQL Authentication)
• Whenever you instantiate a CRecordset-derived object, pass the address of the CDatabase-derived class into its constructor

Downloads