Viacheslav Eremin | EventLogger - example of Task.Factory.FromAsync, Task.Run, ReaderWriterLock, Interlocked.Increment, Stream.BeginWrite, SyncLock, Timeout, AsyncCallback, IAsyncResult, String.Format, Timespan.

(NET) NET (2022)

EventLogger - example of Task.Factory.FromAsync, Task.Run, ReaderWriterLock, Interlocked.Increment, Stream.BeginWrite, SyncLock, Timeout, AsyncCallback, IAsyncResult, String.Format, Timespan.

This is extremely short and simple program, but very useful for beginners to lean Visual Basic. This program only write events to text file from multi threading application, but doing this simple job need experience on VB.NET, therefore I decide to show my code for beginners.

This log also can be deleted in any time.

This is a schema to perform this log.

In the output window you can see a message log for increase timeout.

And this is my code.

   1:  Imports System.ComponentModel.DataAnnotations

   2:  Imports System.Globalization

   3:  Imports System.IO

   4:  Imports System.Text

   5:  Imports System.Threading

   6:  Imports System.Threading.Tasks

   7:  Imports Telerik.WinControls.UI.Barcode.Symbology

8:

   9:  Public Module TxtLogger

  10:      Dim RWL As ReaderWriterLock = New ReaderWriterLock()

  11:      Dim Timeout As TimeSpan = TimeSpan.FromMilliseconds(100)

  12:      Dim TimeoutLock As New Object

  13:      Dim Counter As Integer

  14:      Const MsgLength As Integer = 70

  15:      Public Sub WriteLog(Msg As String, Str1 As StringBuilder)

  16:          Interlocked.Increment(Counter)

  17:  Again:

  18:          Try

  19:              RWL.AcquireWriterLock(Timeout)

  20:              Try

  21:                  Str1.AppendLine($"{Counter},{RWL.WriterSeqNum},{Now.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)},{Msg.Substring(0, Math.Min(MsgLength - 20, Msg.Length))}".PadRight(MsgLength - 2) & vbCrLf)

  22:                  Using Stream = File.Open("Time.csv", FileMode.OpenOrCreate, FileAccess.Write)

  23:                      Dim T As Task = Task.Factory.FromAsync(Function(Callback As AsyncCallback, State As Object)

  24:                                                                 Stream.Position = RWL.WriterSeqNum * MsgLength

  25:                                                                 Return Stream.BeginWrite(Text.UTF8Encoding.UTF8.GetBytes(Str1.ToString), 0, MsgLength, Callback, State)

  26:                                                             End Function,

  27:                                                 Sub(X As IAsyncResult)

  28:                                                     Stream.EndWrite(X)

  29:                                                 End Sub,

  30:                                                 Nothing)

  31:                      T.Wait()

  32:                      Stream.Close()

  33:                  End Using

  34:              Finally

  35:                  RWL.ReleaseWriterLock()

  36:                  Str1 = Nothing

  37:              End Try

  38:          Catch ex As Exception

  39:              Console.WriteLine($"{Counter},{RWL.WriterSeqNum},{Now.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)},{Msg},{ex.Message}" & vbCrLf)

  40:              SyncLock TimeoutLock

  41:                  Timeout = Timeout.Add(TimeSpan.FromMilliseconds(100))

  42:              End SyncLock

  43:              GoTo Again

  44:          End Try

  45:      End Sub

46:

  47:  End Module

Update, write to many files and with file suffix.

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