CDataConnection class
Manages the connection with the data source.
Syntax
class CDataConnection
Requirements
Header: atldbcli.h
Members
Methods
| Name | Description |
|---|---|
CDataConnection::CDataConnection |
Constructor. Instantiates and initializes a CDataConnection object. |
CDataConnection::Copy |
Creates a copy of an existing data connection. |
CDataConnection::Open |
Opens a connection to a data source using an initialization string. |
CDataConnection::OpenNewSession |
Opens a new session on the current connection. |
Operators
| Name | Description |
|---|---|
CDataConnection::operator BOOL |
Determines whether the current session is open or not. |
CDataConnection::operator bool |
Determines whether the current session is open or not. |
CDataConnection::operator CDataSource& |
Returns a reference to the contained CDataSource object. |
CDataConnection::operator CDataSource* |
Returns a pointer to the contained CDataSource object. |
CDataConnection::operator CSession& |
Returns a reference to the contained CSession object. |
CDataConnection::operator CSession* |
Returns a pointer to the contained CSession object. |
Remarks
CDataConnection is a useful class for creating clients because it encapsulates necessary objects (data source and session) and some of the work you need to do when connecting to a data source
Without CDataConnection, you have to create a CDataSource object, call its OpenFromInitializationString method, then create an instance of a CSession object, call its Open method, then create a CCommand object and call its Open* methods.
With CDataConnection, you only need to create a connection object, pass it an initialization string, then use that connection to open commands. If you plan on using your connection to the database repeatedly, it's a good idea to keep the connection open, and CDataConnection provides a convenient way to do that.
Note
If you are creating a database application that needs to handle multiple sessions, you will need to use OpenNewSession.
CDataConnection::CDataConnection
Instantiates and initializes a CDataConnection object.
Syntax
CDataConnection();
CDataConnection(const CDataConnection &ds);
Parameters
ds
[in] A reference to an existing data connection.
Remarks
The first override creates a new CDataConnection object with default settings.
The second override creates a new CDataConnection object with settings equivalent to the data connection object you specify.
CDataConnection::Copy
Creates a copy of an existing data connection.
Syntax
CDataConnection& Copy(const CDataConnection & ds) throw();
Parameters
ds
[in] A reference to an existing data connection to copy.
CDataConnection::Open
Opens a connection to a data source using an initialization string.
Syntax
HRESULT Open(LPCOLESTR szInitString) throw();
Parameters
szInitString
[in] The initialization string for the data source.
Return value
A standard HRESULT.
CDataConnection::OpenNewSession
Opens a new session using the current connection object's data source.
Syntax
HRESULT OpenNewSession(CSession & session) throw();
Parameters
session
[in/out] A reference to the new session object.
Remarks
The new session uses the current connection object's contained data source object as its parent, and can access all of the same information as the data source.
Return value
A standard HRESULT.
CDataConnection::operator BOOL
Determines whether the current session is open or not.
Syntax
operator BOOL() throw();
Remarks
Returns BOOL (MFC typedef) value. TRUE means the current session is open; FALSE means the current session is closed.
CDataConnection::operator bool (OLE DB)
Determines whether the current session is open or not.
Syntax
operator bool() throw();
Remarks
Returns a bool (C++ data type) value. true means the current session is open; false means the current session is closed.
CDataConnection::operator CDataSource&
Returns a reference to the contained CDataSource object.
Syntax
operator const CDataSource&() throw();
Remarks
This operator returns a reference to the contained CDataSource object, allowing you to pass a CDataConnection object where a CDataSource reference is expected.
Example
If you have a function (such as func below) that takes a CDataSource reference, you can use CDataSource& to pass a CDataConnection object instead.
void SourceFunc(const CDataSource& theSource)
{
CComVariant var;
theSource.GetProperty(DBPROPSET_DATASOURCEINFO, DBPROP_DATASOURCENAME, &var);
}
CDataConnection dc;
dc.Open(szInit);
SourceFunc(dc);
CDataConnection::operator CDataSource*
Returns a pointer to the contained CDataSource object.
Syntax
operator const CDataSource*() throw();
Remarks
This operator returns a pointer to the contained CDataSource object, allowing you to pass a CDataConnection object where a CDataSource pointer is expected.
See operator CDataSource& for a usage example.
CDataConnection::operator CSession&
Returns a reference to the contained CSession object.
Syntax
operator const CSession&();
Remarks
This operator returns a reference to the contained CSession object, allowing you to pass a CDataConnection object where a CSession reference is expected.
Example
If you have a function (such as func below) that takes a CSession reference, you can use CSession& to pass a CDataConnection object instead.
void SessionFunc(const CSession& theSession)
{
XACTTRANSINFO info = {0};
HRESULT hr = theSession.GetTransactionInfo(&info);
wprintf_s(_T("GetTransactionInfo returned %x\n"), hr);
}
CDataConnection dc;
dc.Open(szInit);
SessionFunc(dc);
CDataConnection::operator CSession*
Returns a pointer to the contained CSession object.
Syntax
operator const CSession*() throw();
Remarks
This operator returns a pointer to the contained CSession object, allowing you to pass a CDataConnection object where a CSession pointer is expected.
Example
See operator CSession& for a usage example.
See also
OLE DB consumer templates
OLE DB consumer templates reference