DataAdapter is not closing connection by itself - mysql

Question

As we know that DataAdapter opens and closes a Connection if it is not already open. But with my code it opens but not close..I am using MySql.Data.MySqlClient.MySqlDataAdapter, not sure what I am doing wrong. below is my code
Public Function GetDT(ByVal SqlQuery As String, ByVal ConString As String) As DataTable
Dim da As New MySql.Data.MySqlClient.MySqlDataAdapter(SqlQuery, ConString)
Dim ds As New DataSet
da.Fill(ds)
GetDT = ds.Tables(0)
da.Dispose()
ds.Dispose()
da = Nothing
ds = Nothing
End Function
I am using this connection string:"server=localhost;port=3306;user=someuser;pwd=somepassword;database=mydatabasename;Allow Zero Datetime=True;"
while debugging the code I found as soon as DataAdapter.fill executes its start a connection thread, but no where connection is getting close as thread remains in SLEEP state . Please check the below image.
Can any one please help me on this ?
Thanks

Answer 1

Its normal behavior because ADO.NET uses Connection Pooling with SQL Server by default. From MSDN:
http://msdn.microsoft.com/en-US/library/8xx3tyca(v=vs.110).aspx
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.
....
The connection pooler removes a connection from the pool after it has
been idle for approximately 4-8 minutes,...
The effect of "using" or "dispose" in the DataAdapter is the same. "using" ensures that dispose is executed, even if an exception happends. Is the same as using a try / finally statment and put the "dispose" on the finally section.

Answer 2

The connection only closes itself when you use a Using directive, the Using statement can be used on any object that implements the IDisposable interface.
In the Dispose() method of the DataAdapter the connection is closed before disposing the object.
using it correctly would be something like this.
Public Function GetDT(ByVal SqlQuery As String, ByVal ConString As String) As DataTable
Using da As New MySql.Data.MySqlClient.MySqlDataAdapter(SqlQuery, ConString)
Dim ds As New DataSet
da.Fill(ds)
GetDT = ds.Tables(0)
da.Dispose() //because you are now using a 'Using' statement, this method is not necessary anymore.
ds.Dispose()
da = Nothing
ds = Nothing
End Using
End Function