VB.NET - Closing Connection object and command object - vb.net

Question

Please have a look at the code below:
Public Class Form1
Private _ConString As String
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim objDR As SqlDataReader
Dim objCommand As SqlCommand
Dim objCon As SqlConnection
Dim id As Integer
Try
_ConString = ConfigurationManager.ConnectionStrings("TestConnection").ToString
objCon = New SqlConnection(_ConString)
objCommand = New SqlCommand("SELECT * FROM Person")
objCommand.Connection = objCon
objCon.Open()
objDR = objCommand.ExecuteReader(ConnectionState.Closed)
Do While objDR.Read
id = objDR("URN")
Loop
objDR.Close() 'line 16
Catch ex As Exception
throw
Finally
End Try
End Sub
End Class
The connection object is closed on line 16. Please have a look at the code below:
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim objDR As SqlDataReader
Dim objCommand As SqlCommand
Dim objCon As SqlConnection
Dim id As Integer
Try
_ConString = ConfigurationManager.ConnectionStrings("TestConnection").ToString
objCon = New SqlConnection(_ConString)
objCommand = New SqlCommand("SELECT * FROM Person")
objCommand.Connection = objCon
objCon.Open()
Using objCon
Using objCommand
objDR = objCommand.ExecuteReader()
Do While objDR.Read
id = objDR("URN")
Loop
End Using
End Using
objDR.Close() 'line 16
Catch ex As Exception
throw
Finally
End Try
End Sub
I notice in both cases that the connection object and command object both still have state after they are closed (either by closing the data reader as per code sample 1 or moving outside the Using statement as per code sample 2). Could this be a source of a memory leak?

Answer 1

You should be doing something like this...
Using Conn as new SqlConnection(_ConString)
Dim cmd as New SqlCommand(Conn, "Select * FROM Person");
id = Convert.ToInt32(cmd.ExecuteScalar())
End Using
Wrap this in a try if you must, but only if you are going to handle it in some way. (A simple "Throw" is not handling anything.)
You are also using a DataReader (iterative, forward only) data access component to get a single value. You may want to use an ExecuteScalar() to simplify that code.
Aside from that, do not confuse "Disposed" as being the same as "Closed". The .NET framework manages garbage collection for you. If you want to dispose the connection and command objects, call .Dispose() on them (but the Using will take care of this for you!!!)

Answer 2

re: Could this be a source of a memory leak?
no, it shouldn't be.
also, this:
objDR = objCommand.ExecuteReader()
Do While objDR.Read
id = objDR("URN")
Loop
looks bad because it iterates through all the rows and overwriting the id values. The last row set ends up with the value in ID. You're taking one result from a set of more than one rows. If you just want the max(URN) from Person, you can write your command to return that result.