vb.net - Mysql connections are not closing using Sub routines - mysql

Question

I'm using the code below in a module that I can then call from anywhere else in the program to manage my mysql database connection. I just call the dbExecute sub and then it in turn is supposed to open a DB connection using the manageConnection(true) statement and then close the connection using manageconnection(false). The problem I'm having is that after the dbC.Close statement the connection to the DB never drops so I just accumulate connections until the max hits at 104 and then I get a connection error. I have tried to add dbC.dispose, dbC = Nothing and nothing in that else statement for CloseConnection seems to matter. The connections remains open. I'm wondering if it's because I'm passing my msr into dbExecute ByRef, so it's holding the connection open for that dataset? If so how can I work around getting my DataReader passed back to the calling procedure? I'm trying to manage me DB connections after each DB call, but currently not doing a good job at it! Hope another set of eyes can help me understand my problem.
I'm using the following as an example of how I call the DB connection now:
Public Class frmLogin
Dim db As New DBCon
Dim msr As MySqlDataReader = Nothing
Dim Query As String
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles btnCheckConn.Click
Query = "Select username from db.userstable"
db.dbExecute(Query, msr)
******The following is the Module code****************
Imports MySql.Data.MySqlClient
Public Class DBCon
Dim dbC As MySqlConnection
Public Sub ManageConnection(ByVal CloseConnection As Boolean)
Try
dbC = New MySqlConnection("server=localhost; userid=****; password=****; database=****;")
If CloseConnection = True Then
If dbC.State = ConnectionState.Closed Then _
dbC.Open()
Else
dbC.Close()
End If
Catch ex As Exception
MsgBox("DB Connection failure:" & ex.Message)
End Try
End Sub
Public Sub dbExecute(ByVal q As String, ByRef msr As MySqlDataReader)
Try
ManageConnection(True) 'Open connection'
Dim msc As New MySqlCommand(q, dbC)
msr = msc.ExecuteReader
ManageConnection(False) 'Close connection'
Catch ex As Exception
MsgBox("Error " & ex.Message)
End Try
End Sub
Tried users suggestions below and was still seeing a connection hang when looking at the mysql workbench-performance-client connections. So I changed my ManageConnection code to the following below just to test and called it directly as :dbCon.ManageConnection (true) and as soon as the .open line fires I see a new connection to mysql, but the .close, .dispose and =nothing lines do not clear out that connection. Do I have something set wrong in mysql? If .open creates a new connection, I'm not sure why the very next line of .close wouldn't get rid of it. I do believe that's the root of my problem though. Hopefully someone has run into this before. Let me know your thoughts.
Public Sub ManageConnection(ByVal CloseConnection As Boolean)
Try
If CloseConnection = True Then
dbC = New MySqlConnection("server=localhost; userid=****; password=****; database=dbname;")
dbC.Open()
dbC.Close()
dbC.Dispose()
dbC = Nothing
Else
dbC.Close()
dbC.Dispose()
End If
Catch ex As Exception
MsgBox("DB Connection failure:" & ex.Message)
End Try

Answer 1

There are several ways to cope with these database connection leaks. Using ... End Using is probably the best. But you can also do dbC.Dispose() or set dbC = Nothing when you're done with a connection object.
The point is to, without fail, Dispose() the connection object when you're done with it. Using does that for you even if your program hits exceptions.
Try something like this in your main program. And stop using that ManageConnection sub. It's practically guaranteed to leak connections.
Using dbC as New MySqlConnection("server=localhost; userid=****; password=****; database=****;")
Dim msc As New MySqlCommand(q, dbC)
msr = msc.ExecuteReader
...
End Using