Viacheslav Eremin | Mutlithreading InfoMessagBox by ConcurrentQueue, Interlocked and Timer.

(NET) NET (2016)

Mutlithreading InfoMessagBox by ConcurrentQueue, Interlocked and Timer.

In one threading application for information message I using that solution How to intercept exception & console output & debug trace and show it in textbox, but in muttithreading application I usually show information message in this way Оновлення StatusLabel з потоку BackGroundWorker - приклад застосування Action, Delegate, Invoke, AddressOf, Extension, Expression or by the code I descripted below.

 136:  #Region "InfoMessage"

 137:

 138:      Dim InfoMessageQueue As ConcurrentQueue(Of String) = New ConcurrentQueue(Of String)

 139:      Dim MessageCount As Integer = 0

 140:

 141:      Public Sub InfoMessage(Msg As String)

 142:          Me.InvokeOnUiThreadIfRequired(Sub()

 143:

 144:                                            Threading.Interlocked.Increment(MessageCount)

 145:                                            If InfoCheckBox.Checked Then

 146:                                                InfoMessageQueue.Enqueue(MessageCount.ToString & ": " & Msg & vbCrLf)

 147:                                            End If

 148:                                        End Sub)

 149:      End Sub

 150:

 151:   Dim WithEvents Timer1 As Timers.Timer

 152:      Sub StartTimer()

 153:          Timer1 = New Timer(1000)

 154:          Timer1.Enabled = True

 155:          Timer1.Start()

 156:      End Sub

 157:

 158:      Sub StopTimer()

 159:          Timer1.Enabled = False

 160:          Timer1.Stop()

 161:      End Sub

 162:

 163:

 164:

 165:      Private Sub Timer1_Elapsed(sender As Object, e As ElapsedEventArgs) Handles Timer1.Elapsed

 166:          Me.InvokeOnUiThreadIfRequired(Sub()

 167:                                            TimeLabel.Text += Timer1.Interval / 1000

 168:                                            TimeLabel.Refresh()

 169:                                        End Sub)

 170:          Me.InvokeOnUiThreadIfRequired(Sub()

 171:                                            Message.Text = ""

 172:                                            Dim OneItem As String = ""

 173:                                            If InfoCheckBox.Checked Then

 174:                                                While (Not InfoMessageQueue.IsEmpty)

 175:                                                    InfoMessageQueue.TryDequeue(OneItem)

 176:                                                    Message.Text &= OneItem

 177:                                                End While

 178:                                                Message.SelectionStart = Message.TextLength

 179:                                                Message.ScrollToCaret()

 180:                                                Message.Refresh()

 181:                                            End If

 182:                                        End Sub)

 183:      End Sub

 184:

 185:  #End Region

This is not full correct code, it's possible to doubling message number, because Threading.Interlocked.Increment and InfoMessageQueue.Enqueue is not atomic operation, more correctly way to use class Monitor, SyncLock statement or <Runtime.CompilerServices.MethodImplAttribute(Runtime.CompilerServices.MethodImplOptions.Synchronized)> attribute for needed method.

But in this case this unblocked code is a best way.

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