Question

Which use of connection management is better while developing a windows based application which uses a Database as its data store? What about web-based applications?

1. when user loads the first form of an application, the global
   connection opens and on closing the last form of the application
   the connection closes and disposes.
2. for each form within the application, there is a local connection
   (form scope) and when user wants to perform an operation like
   insert, update, delete, search, … the application uses the
   connection and by unloading the form the connection also closes and
   disposes.
3. for every operation within a form of an application, there is a
   local connection (procedure scope) and when user wants to perform
   an operation like insert, update, delete, search, … the
   application uses procedure connection and at the end of every
   procedure within the form, the connection also closes and disposes.

Answer 1

Go with #3

You should try to only ever keep connections open for just as long as is required.

Also have a look at

• Understanding Connection Pooling
• SQL Server Connection Pooling
  (ADO.NET)

Connecting to a database server
typically consists of several
time-consuming steps. A physical
channel such as a socket or a named
pipe must be established, the initial
handshake with the server must occur,
the connection string information must
be parsed, the connection must be
authenticated by the server, checks
must be run for enlisting in the
current transaction, and so on.

In practice, most applications use
only one or a few different
configurations for connections. This
means that during application
execution, many identical connections
will be repeatedly opened and closed.
To minimize the cost of opening
connections, ADO.NET uses an
optimization technique called
connection pooling.

Connection pooling reduces the number
of times that new connections must be
opened. The pooler maintains ownership
of the physical connection. It manages
connections by keeping alive a set of
active connections for each given
connection configuration. Whenever a
user calls Open on a connection, the
pooler looks for an available
connection in the pool. If a pooled
connection is available, it returns it
to the caller instead of opening a new
connection. When the application calls
Close on the connection, the pooler
returns it to the pooled set of active
connections instead of closing it.
Once the connection is returned to the
pool, it is ready to be reused on the
next Open call.