Page 1 of 7

1. Introduction
2. Synchronization, Interlocked, SyncLock and Monitor Classes
3. WaitHandle, AutoResetEvent and ManualResetEvent Classes
4. Mutex Class
5. ReaderWriterLock Object
6. COM+ and Windows Forms Synchronization
7. Volatile Keyword & Conclusion

Comments

1. syed nizamuddin
   10 Jul 2009 at 05:08

   I need to lock the Log file once someone is using it and second person shouldn't able to write in log file. The code is shown below :

   Imports System Imports System.IO

   Module FileTransfer

   Sub Main()
       Dim dtStart As Date = Now(), dtEnd As Date = Now()
       Dim intNoofFiles As Integer = 0
       Dim strLogFileName As String = "C:\Log\FileTransferLog_" + dtStart.Year.ToString().PadLeft(4, "0") + dtStart.Month.ToString().PadLeft(2, "0") + dtStart.Day.ToString().PadLeft(2, "0") + ".txt"
       Dim oWrite As StreamWriter = File.AppendText(strLogFileName)
   
   
       oWrite.WriteLine("=================================================================================================")
       oWrite.WriteLine("Starting PRESTO File Transfer Job. Start Date: " + dtStart.ToString())
       oWrite.WriteLine("=================================================================================================")
   
       ' Call main job 
       subMoveFiles("C:\Presto\Inbound\", "c:\PRESTO_FILES\", oWrite, intNoofFiles)
   
       dtEnd = Now()
       oWrite.WriteLine("=================================================================================================")
       oWrite.WriteLine("Completed PRESTO File Transfer Job. End Date: " + dtEnd.ToString())
       oWrite.WriteLine("Total number of files transferred: " + intNoofFiles.ToString())
       oWrite.WriteLine("=================================================================================================")
   
       oWrite.Close()
   End Sub
   
   Public Sub subMoveFiles(ByVal strSrcDirectory As String, ByVal strDstDirectory As String, ByRef oWrite As StreamWriter, ByRef intNoofFiles As Integer)
       If strDstDirectory(strDstDirectory.Length - 1) <> Path.DirectorySeparatorChar Then
           strDstDirectory += Path.DirectorySeparatorChar
       End If
   
       If Not Directory.Exists(strDstDirectory) Then
           Directory.CreateDirectory(strDstDirectory)
       End If
   
       Dim strFileSystemEntries As String() = Directory.GetFileSystemEntries(strSrcDirectory)
       Dim strFileSystemEntry As String = ""
       For Each strFileSystemEntry In strFileSystemEntries
           If (Directory.Exists(strFileSystemEntry)) Then
               'Sub directories
               subMoveFiles(strFileSystemEntry, strDstDirectory + Path.GetFileName(strFileSystemEntry), oWrite, intNoofFiles)
           Else
               ' get the created date / last written date
               If DateAdd(DateInterval.Minute, 5, File.GetLastWriteTime(strFileSystemEntry)) < Now() Then
                   oWrite.WriteLine("Transferring File: " + strFileSystemEntry)
                   ' First Copy the file to the destination and then Delete
                   File.Copy(strFileSystemEntry, strDstDirectory + Path.GetFileName(strFileSystemEntry), True)
                   File.Delete(strFileSystemEntry)
                   intNoofFiles = intNoofFiles + 1
                   oWrite.WriteLine("Completed Transferring File: " + strFileSystemEntry)
               End If
           End If
       Next
   End Sub
   

   End Module

2. momo200k
   31 Jul 2008 at 11:28

   Bundle of thanks to the author, it is very help full
    

3. stixoffire
   13 Dec 2006 at 07:35

   As somewhat of an advanced "newbie" I have read many articles on Multithreading, and am at a loss

   Do I need to have a delegate and call the delegate when I am using threading ?

    

   Lets say I have a datatable with 5 million rows and I need to iterate through each row - grab some info , process that info (translate it) and then save it somewhere else. For example insert it inot a completely different database (and maybe even RDBMS - Architectur)

   Now I currently for each row - but that takes a lot of time.

   I would like to spawn a (Flexible Number of threads) to do the row processing - Will my For each move on as each thread runs. So I start Thread(1) will the next trigger, and I have a new row and can start thread(2) and so on. Also my Subroutine, must

4. John Spano
   19 Jan 2006 at 19:33

   Yes, but I decided not to go into detail since it's a vb.net article and you can't use it

5. Jon Skeet
   11 Jan 2006 at 08:47

   Volatility means a lot more than is described in the article. It doesn't just affect the variable which has the volatile modifed; it affects the whole memory model for sections of code involving access to that variable.
   

   
   I agree that there's no use of volatile which can't be semantically achieved using locks, and indeed I generally prefer to use locks myself. However, there is a speed difference between acquiring a lock and just using a volatile variable - in a very few cases it might be significant. I'm surprised VB.NET doesn't have any way of specifying this.
   

   
   See the volatility page of my C# threading article for more information.
   

   
   Jon Skeet
   

6. Developer Fusion Bot
   01 Jan 1999 at 00:00

   This thread is for discussions of Multithreading in VB.NET.

John Spano cofounder and CTO of NeoTekSystems, a Greenville, South Carolina technology consulting company. NeoTekSystems offers IT consulting, custom programming, web design and web hosting. We spe...