Working with write queues and multi threading - vb.net

Question

I have a process running in a separate thread which reads data over Ethernet and raises an event for each read. Then, this data is processed over a tree of classes. At the top of my class tree, I want to store the processed data to SQL tables. This read rate can be rather fast and often at times but on average its slower than my write rate to SQL. This is why I want a queue. Also I want my window not to freeze, so I want a separate thread.
The code below works but I'm fairly inexperienced in multi threading, is this a good and robust way to accomplish my task?
Private addLogQueue As New Queue
Private dequeueing As Boolean = False
Public Sub addLogHandler(ByVal machineName As String, ByVal LogTime As Date, ByVal EventLog As String, ByVal EventValue As String)
addLogQueue.Enqueue("INSERT INTO ... some SQL CODE")
Dim Thread1 As New System.Threading.Thread(AddressOf addLog)
Thread1.Start
End Sub
Private Sub addLog()
If Not dequeueing Then
dequeueing = True
While addLogQueue.Count <> 0
Try
SQLCon.Open()
SQLCmd = New SqlCommand(addLogQueue.Dequeue(), SQLCon)
SQLCmd.ExecuteNonQuery()
SQLCon.Close()
Catch ex As Exception
MsgBox(ex.Message)
If SQLCon.State = ConnectionState.Open Then
SQLCon.Close()
End If
End Try
End While
dequeueing = False
End If
End Sub

Answer 1

I would refer you to the article: Beginners Guide to Threading. Also, for performance reasons you may want to keep the thread open, and the database connection open and simply use a wait event to determine if the queue should be checked for more entries. See this article: An Overview of Synchronization. Keeping the connection open would really depend on the frequency of arrival of messages. Very frequent: keep connection open, intermittent: Close after use.
Dim Thread1 As New System.Threading.Thread(AddressOf addLog)
Private Shared mre As New ManualResetEvent(False)
Private addLogQueue As New Queue
Private shutDown as boolean = false
Public Sub Main
Thread1.Start
End Sub
Public Sub addLogHandler(ByVal machineName As String, ByVal LogTime As Date, ByVal EventLog As String, ByVal EventValue As String)
addLogQueue.Enqueue("INSERT INTO ... some SQL CODE")
mre.Set()
End Sub
Private Sub addLog()
dim cmdString as String
Try
Using SQLCon as New SQLConnection
SQLCon.Open()
While Not shutDown
mre.WaitOne()
mre.Reset()
While addLogQueue.Count <> 0
cmdString = addLogQueue.Dequeue()
SQLCmd = New SqlCommand(cmdString, SQLCon)
SQLCmd.ExecuteNonQuery()
End While
End While
End Using
Catch ex As Exception
My.Application.Log.WriteException(ex,TraceEventType.Error, cmdString)
End Try
End Sub
Also, you may want to lookup a few articles on writing services as this sort of thing works very much better as a service, if you want the program to do unattended monitoring. Also, you could have one thread accepting the command strings and adding them to the queue, and the second thread writing them to the database.