Examples of maintaining memory with database connections for VB.net - vb.net

Question

I have a particular problem in database connection disposal and despite there being a lot of back and forth over disposal of connections, datasets, and datatables I can't quite wrap my head around it as a new VB coder. My project has a form with a simple "Import Database" button which opens a connection. Lets assume I have a database with several Datasets and datatables that take up a bunch of memory so I have to be careful how I open and close things. I have a button to close the database when done with it. The code briefly looks like this and does not throw me errors (i.e. I can connect, get the right data and then close the database without an error being thrown)
Public ConnectedDB as DataBaseOps
Class Form1
Private Sub ImportDatabaseButton(sender as object, e and eventargs) handles ImportDatabasebutton.click
'Open filedialog and return the path, etc.
strPATH = OpenFileDialogMaster(...my filters here...)
ConnectedDB.OpenDatabase(strPath)
End Sub
Private Sub populateDSDT(....)
'...populate my datasets which then populate my datagrids
ConnectedDB.PopulateMyDataSet()
'...populate my datagrids
End sub
Private Sub CloseDatabaseButton(sender as object, e and eventargs) handles CloseDatabaseButton.click
ConnectedDB.CloseDatabase()
'Can I put something here to clean up the DatabaseOPs class?
End Sub
End Class
Now in a separate class
Private Class DataBaseOps
Public OpenCon As OleDb.OleDbConnection
Public Sub OpenDataBase(strPath as String)
'My.Settings.ConnectionString is a variable in App.Config
OpenCon = New OleDb.OleDbConnection(My.Settings.ConnectionString & strPath)
OpenCon.Open()
End Sub
Public Sub PopulateMyDataSet()
'...Populate my datasets and tables based on data from the database
'...Note that for the adapters I include "Using" to help keep those clean when I no longer need them
End sub
Public Sub CloseDatabase()
Try
OpenCon.Close()
Catch ex As Exception
MessageBox.Show("No Database file loaded.")
End Try
End Sub
Overrides Sub Finalize()
'...Datasets get .Dispose() which is a topic of its own elsewhere.
OpenCon.Dispose()
End Sub
End Class
Keep in mind there are other ways of doing this but the key factor here is to open the connection, keep it open to populate datagrids, do some other work in the database, and then close it releasing the connection and datasets memory.
My problem is I've tried various means to limit the scope of "ConnectedDB" and its datasets including putting a Finalize() sub into the process in an attempt to remove it from memory. I also toyed with scoping but neither of these ideas work perfectly and it seems to retain items in memory.
Using my general code what can I do to clean up the memory resource here? As a relatively new VB.net coder, am I missing something obvious (like I could maybe inherit one class to the other instead of calling them?)

Answer 1

Keep your connections local to where they are used. Then you can use Using...End Using blocks to ensure that they are closed and disposed.
Thanks to Duncan Edwards Jones for this quote.
"A database connection is like a refrigerator door - You only open it
when you need something, you only take out what you need, and you
close it as soon as you have taken out what you need. "
A DataSet can hold more than one DataTable. I am not sure why you would need more than one DataSet.
Class Form1
Private ConnectedDB As DataBaseOps
Private ds As DataSet
Private Sub ImportDatabaseButton(sender As Object, e And eventargs) Handles ImportDatabaseButton.click
Dim OpenDial As New OpenFileDialog
'Open filedialog and return the path, etc.
Dim strPATH = OpenDial.FileName
ConnectedDB = New DataBaseOps(strPATH)
End Sub
Private Sub populateDSDT()
'...populate my datasets which then populate my datagrids
ds = ConnectedDB.PopulateMyDataSet()
'...populate my datagrids
End Sub
End Class
Public Class DataBaseOps
Private DBFile As String
Public Sub New(file As String)
DBFile = file
End Sub
Public Function PopulateMyDataSet() As DataSet
Dim ds As New DataSet
Using OpenCon As New OleDb.OleDbConnection(My.Settings.ConnectionString & DBFile)
OpenCon.Open() 'But don't do this until directly before the .Execute...
'...Populate my datasets and tables based on data from the database
'...Note that for the adapters I include "Using" to help keep those clean when I no longer need them
End Using
Return ds
End Function
End Class

Answer 2

Add this two lines in your Finalize method after OpenCon.Dispose()
GC.Collect()
GC.WaitForPendingFinalizers()