Overview
Through this article I want to present readers with an ODBCManager class that allows user to
have a list of ODBC Drivers installed in his/her system. Also this class gives the users all system as well as user
DSNs.
Details
(Experienced readers can ignore/skim through this section. I have lifted most of the
following stuff from the Internet)
About DSN: DSN is an acronym for Data Source Name. It's a simple and standard way to describe how
to connect to a data source (database) using an ODBC driver. More importantly, using a DSN means we can
change the location of our data by updating the DSN, no update to our application required. But we have to
keep in mind that DSN's only describe ODBC connections, not OLEDB connections.
There are three types of DSN's; system, user, and file.
System DSN's and User DSN's differ only in who can access them on the system. A File DSN, however, is not
really a datasource. It is a file that contains all the connection parameters used to connect directly to
an ODBC driver. System and user DSN's are windows registry based, while File DSN's are stored in the file
system. We normally create and administer DSN's through the ODBC Data Source Administrator, found in
Control Panel on NT/9x machines, or in Administrative Tools for Win2K machines. However, there is nothing
magical about editing DSN's. We can use regedit to view/modify user or system DSN's, and notepad works fine for file DSN's.
Most information about DSN's is stored in the registry.
- HKEY_LOCAL_MACHINE\Software\ODBC\ODBCINST.INI contains a list of all ODBC drivers installed on the machine.
- HKEY_LOCAL_MACHINE\Software\ODBC\ODBC.INI contains all of system DSN's stored as separate subkeys.
ODBC.INI has two other subkeys, "ODBC Data Sources" that contains a list of all system DSN's, and
"ODBC FileDSN", which contains the name of the folder where File DSN's are stored
("C:\Program Files\Common Files\ODBC\Data Sources" is the default). User DSN's are stored in
HKEY_CURRENT_USER\Software\ODBC\ODBC.INI.
Choosing which type of DSN to use, depends on how our application works. In almost all cases a system
DSN works. If we use a user DSN, then we'll have to do some extra work to make sure the DSN gets created
when a user new to that machine logs in for the first time.
About ODBC Driver: An ODBC driver acts as a �translator� between an application and a database.
There are drivers available for many databases like Oracle, MS Access, SQL Server, Foxbase etc. Main use
of these drivers is, without having a client program supplied by the vendor of the data base, these drivers
allow us to interact with
databases. For example, let us suppose we have a Oracle Database which has some tables in it. Now If we have
a Oracle ODBC Driver installed in our machine, then we don't need to have the Oracle S/W (Expensive) to talk with that
database. But We have write our own routines to talk to the database using ODBC provided by C++/C# or
whatever language we want to use (That support ODBC Driver API).
How this Class works
ODBCManager class is defined in 'ODBCMngr' namespace. This class is present in the DLL
ODBCMngr.DLL. This class has all static methods. So no instance needs to be created
(In fact users can't create one, since the class is following singleton pattern). Apart from the
ODBCManager, the DLL has following other classes ODBCDriver and
ODBCDSN.
This ODBCManager class has following static methods.
public static ODBCDriver[] GetODBCDrivers();
public static ODBCDriver GetODBCDriver(string driverName);
public static ODBCDSN[] GetSystemDSNList();
public static ODBCDSN GetSystemDSN(string dsnName);
public static ODBCDSN[] GetUserDSNList();
public static ODBCDSN GetUserDSN(string dsnName);
public static RegistryKey OpenComplexSubKey(RegistryKey baseKey,
string complexKeyStr, bool writable);
Except for the method 7 signatures of the above methods are self explanatory. I added method 7
to the class, since I don't find any method '.Net framework Registry class' that gives a
RegistryKey for a nested key. For example to get the "Software" subfolder in
HKEY_LOCAL_MACHINE root folder of registry following method call can be used.
RegistryKey fianlKey = (Registry.LocalMachine).OpenSubKey("Software");
Now if we want the key for "Software\ODBC\" in HKEY_LOCAL_MACHINE root folder of
registry following method calls can be used.
RegistryKey fianlKey = (Registry.LocalMachine).OpenSubKey("Software");
fianlKey = fianlKey.OpenSubKey("ODBC");
Now my method (7) can eliminate multiple calls to OpenSubKey() method as done above. So using (7)
RegistryKey finalKey = ODBCManager.OpenComplexSubKey(
Registry.LocalMachine, "Software\ODBC\", false);
Note: Last parameter is a boolean flag that tells the 'OpenComplexSubKey'
method to create a sub folder if it is not present.
Program Notes
Since this is a DLL that has methods we can call, I don't really see the use of writing a client
program. So I am not writing any program using the above DLL. Please note that this is version - I
of the DLL. I will try to add more related stuff to this DLL in future. If I do so, I will update again.
I hope I explained all the things that are need to be explained. If any one of you feel I did some thing
terribly wrong or not clear, please let me know. I will try to correct and/or respond.
