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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http://www.vb-net.com/EventLogger/Index.htm
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