I have a feature whereby a class in a dll displays a form asking a user to clear a fault on a printer before clicking a button to say "Retry". The users have been just hitting retry without bothering to clear the fault so I am now coding an interlock:
The button on the invoked form is disabled until a call is made to an 'enable' method on the form.
This is done with delegate invocation as the events triggering these changes come from other dlls running on different threads.
The form's 'enable' method is wired into an EVENT HANDLER handling an event coming in from a different thread (one that monitors an ethernet IO Server).
The problem I have is that THE "_Fault_StateChanged" EVENT NEVER FIRES. I suspected the cause was the "ShowDialog" and "DialogResult" technique I have used here, but I have used this exact same technique elsewhere in this application.
Any suggestions would be great
See code extract below:
MAIN CLASS excerpt
Public Class StatePrintHandler
Private WithEvents _RetryForm As frmRetryReject
Private Delegate Sub delShowRetryDialog()
Private Delegate Sub delResetEnable()
Private Sub InvokeResetEnable()
Dim del As delResetEnable
del = New delResetEnable(AddressOf ResetEnable)
del.Invoke()
End Sub
Private Sub InvokeRetryDialogue()
Dim del As delShowRetryDialog
del = New delShowRetryDialog(AddressOf ShowRetryDialog)
del.Invoke()
End Sub
Private Sub ShowRetryDialog()
_RetryForm = New frmRetryReject
_RetryForm.Prep()
_RetryForm.ShowDialog()
If (_RetryForm.DialogResult = Windows.Forms.DialogResult.OK) Then
Me._RetryForm.Visible = False
End If
End Sub
Private Sub ResetEnable()
If (Not IsNothing(_RetryForm)) Then
_RetryForm.ResetEnable()
Else
AuditTrail("Retry form not active, no action", True)
End If
End Sub
'Event handler for status change coming in on a different thread
Private Sub _Fault_StateChanged(ByVal sender As Object, ByVal e As Drivers.Common.DigitalSignalChangedEventArgs) Handles _fault.StateChanged
If (e.NewState) Then
AuditTrail("Labeller has faulted out during cycling", True)
Else
InvokeResetEnable()
End If
End Sub
End Class
RETRY FORM CLASS excerpt
Public Class frmRetryReject
Private Delegate Sub delEnable()
Public Event Complete()
Public Sub Prep()
Me.OK_Button.Enabled = False
End Sub
Private Sub OK_Button_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK_Button.Click
Me.DialogResult = System.Windows.Forms.DialogResult.OK
Me.Close()
End Sub
Public Sub ResetEnable()
If (IsHandleCreated) Then
Dim params() As Object = {}
Me.Invoke(New delEnable(AddressOf InvokeEnable), params)
End If
End Sub
Private Sub InvokeEnable()
Me.OK_Button.Enabled = True
End Sub
End Class
Additional detail in response to Daniel's comments
The code is incomplete here, it's an excerpt. The fault object is a subscription to an external library and is a handler for an ethernet IO server.
The _fault StateChanged event fires when a digital input on an IOServer changes. I know the following:
My trace files show the signal change high, this invokes the retry form.
The signal physically changes low again when the retry screen is still showing.
...but the event does not fire
It's as if the application cannot service the event coming in until the ShowDialog/DialogResult completes - but I am confused about this because I understood that the ShowDialog in .NET 2.0 did not block, I should still be able to service events, and have used this same pattern elsewhere in the app.
A couple of things to note:
The MAIN CLASS is instantiated dynamically at runtime via reflection based on configuration.
This is VS2005 SP2
I will post the entire class in another code box if this helps, but it may crowd the scene...
Thanks
Andy
Imports System.IO
Imports ACS.Interfaces
Imports ACS.Pallet
Public Class StateCimPAKPrintHandler
Inherits StateBase
Private WithEvents _ioManager As ACS.Components.DigitalIOManager
Private _config As StateCimPAKPrintHandlerBootstrap
Private CONST_OutcomeOK As String = "OK"
Private CONST_OutcomeRetry As String = "Retry"
Private CONST_OutcomeException As String = "Exception"
Private WithEvents _busy As ACS.Drivers.Common.InputSignal
Private WithEvents _fault As ACS.Drivers.Common.InputSignal
Private WithEvents _print As ACS.Drivers.Common.OutputSignal
Private WithEvents _palletRelease As ACS.Drivers.Common.OutputSignal
Private _labellingInProgress As Boolean
Private _faulted As Boolean
Private _retryScreenInvoked As Boolean
Private WithEvents _timeout As System.Timers.Timer
Private WithEvents _faultTimer As System.Timers.Timer
Private WithEvents _RetryForm As frmRetryReject
Private Delegate Sub delShowRetryDialog()
Private Delegate Sub delResetEnable()
Private Sub InvokeResetEnable()
Dim del As delResetEnable
del = New delResetEnable(AddressOf ResetEnable)
del.Invoke()
End Sub
Private Sub InvokeRetryDialogue()
Dim del As delShowRetryDialog
del = New delShowRetryDialog(AddressOf ShowRetryDialog)
del.Invoke()
End Sub
Private Sub ShowRetryDialog()
_timeout.Stop()
_retryScreenInvoked = True
_RetryForm = New frmRetryReject
_RetryForm.Prep()
AuditTrail("Displaying Retry screen", True)
_RetryForm.ShowDialog()
If (_RetryForm.DialogResult = Windows.Forms.DialogResult.OK) Then
AuditTrail("User clicked RETRY LINE on the RETRY dialogue", True)
_retryScreenInvoked = False
Me._RetryForm.Visible = False
Me.SetOutcome(CONST_OutcomeRetry)
End If
End Sub
Private Sub ResetEnable()
If (Not IsNothing(_RetryForm)) Then
_RetryForm.ResetEnable()
Else
AuditTrail("Retry form not active, no action", True)
End If
End Sub
Public Sub New(ByVal Sequencer As ISequencer, ByVal ParentPlt As ACS.Interfaces.IPallet, ByVal Name As String)
MyBase.New(Sequencer, ParentPlt, Name)
_timeout = New System.Timers.Timer
_faultTimer = New System.Timers.Timer
_config = New StateCimPAKPrintHandlerBootstrap(Me._myIniFileName, Name)
_timeout.Interval = _config.CycleTimeoutMS
_faultTimer.Interval = 750
_retryScreenInvoked = False
_RetryForm = New frmRetryReject
Me._RetryForm.Visible = False
_ioManager = ACS.Components.DigitalIOManager.GetInstance
_busy = _ioManager.GetInput("Busy")
_fault = _ioManager.GetInput("CimPAKFault")
_print = _ioManager.GetOutput("Print")
_palletRelease = _ioManager.GetOutput("PalletRelease")
End Sub
Public Overrides Sub Kill()
_ioManager = Nothing
_RetryForm = Nothing
_busy = Nothing
_fault = Nothing
_print = Nothing
_timeout = Nothing
_faultTimer = Nothing
_pallet = Nothing
End Sub
Public Overrides Sub Execute()
AuditTrail("Pulsing Print Signal", True)
_print.PulseOutput(3000)
_labellingInProgress = True
_timeout.Start()
End Sub
Private Sub _busy_StateChanged(ByVal sender As Object, ByVal e As Drivers.Common.DigitalSignalChangedEventArgs) Handles _busy.StateChanged
_timeout.Stop()
AuditTrail("Busy signal changed to : " & e.NewState, True)
If (e.NewState) Then
_faulted = False
AuditTrail("CimPAK = Busy High", True)
_labellingInProgress = True
Else
AuditTrail("CimPAK = Busy Low", True)
AuditTrail("Wait 750 milliseconds for any faults", True)
_faultTimer.Start()
End If
End Sub
Private Sub _Fault_StateChanged(ByVal sender As Object, ByVal e As Drivers.Common.DigitalSignalChangedEventArgs) Handles _fault.StateChanged
AuditTrail("Fault signal changed to : " & e.NewState, True)
If (e.NewState) Then
If (_labellingInProgress = True) Then
AuditTrail("Labeller has faulted out during cycling", True)
_faulted = True
If (Not _retryScreenInvoked) Then
InvokeRetryDialogue()
End If
Else
AuditTrail("Labeller has faulted out between cycles, no action can be taken", True)
End If
Else
If (_retryScreenInvoked) Then
AuditTrail("Enable button on Retry screen", True)
InvokeResetEnable()
End If
_faulted = False
End If
End Sub
Private Sub _faultTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles _faultTimer.Elapsed
_faultTimer.Stop()
If (_faulted) Then
AuditTrail("System has faulted", True)
Else
AuditTrail("No fault occured, assume pallet is OK to release", True)
AuditTrail("CimPAK cycle complete", True)
_labellingInProgress = False
_palletRelease.PulseOutput(3000)
Me.SetOutcome(CONST_OutcomeOK)
End If
End Sub
Private Sub _timeout_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles _timeout.Elapsed
_timeout.Stop()
AuditTrail("Labeller print cycle timed out", True)
If (Not _retryScreenInvoked) Then
_retryScreenInvoked = True
InvokeRetryDialogue()
InvokeResetEnable()
End If
End Sub
End Class
#Region "Bootstrap"
Public Class StateCimPAKPrintHandlerBootstrap
Private Const CONST_CycleTimeoutMS As String = "CycleTimeoutMS"
Private _CycleTimeoutMS As Long
#Region "Properties"
Public ReadOnly Property CycleTimeoutMS() As Long
Get
Return _CycleTimeoutMS
End Get
End Property
#End Region
Public Sub New(ByVal IniFile As String, ByVal Name As String)
Try
Dim _cfgFile As String = Environ("ACSVAR") & "\" & IniFile
' Check to see if the CFG file exits
If File.Exists(_cfgFile) = False Then
Throw New Exception("Configuration file does not exist: " & _cfgFile)
Else
'Get values
_CycleTimeoutMS = ACS.Utility.Configuration.GetLong(_cfgFile, Name, CONST_CycleTimeoutMS)
End If
Catch ex As Exception
Throw
End Try
End Sub
End Class
#End Region
Try to look at
Visual Basic, Child Thread Blocking Main Thread
answer for in Multithreading example and
New Thread is still blocking UI-Thread
answer from ( me ) for In Model Threading.... Those 2 should give you writen code to start aswell.
It's been a long time since I did any Winforms work, but are you showing the dialog modally? Because that could be the cause of the delegate invokation not arriving.
Asynchronous delegates work by serializing the invokation details into a memory location internal to the framework and then posting a window message to the top-level window for the relevant thread. Modal dialogs work by going into a message processing loop that steals all the messages for the thread so that only that one dialog can respond. You can see how this might conflict.
Related
I am using a class to load a waitgif form (via threading), attributed to #nobugz here. The spawned waitgif form has a cancel button. The problem is that I need the class that spawned the thread (waitgif form) to listen for a cancelled token from the spawned form. So can I feed the token to the threaded waitgif form via a property, so that upon cancellation the parent thread will terminate?
Also, as a general question, whenever t.Source.Cancel is used in a method of an instantiated class, can it be followed by Me.Dispose based on the declaration Implements IDisposable to speed up memory availability without forcing garbage collection?
Public Class PleaseWait
Implements IDisposable
Private mSplash As New Form
Private mLocation As Point
Shared t As New TokenPOC()
Sub New(ByVal location As Point)
mLocation = location
ThreadPool.QueueUserWorkItem(Sub(state) workerThread(), t.Token)
End Sub
Public Sub Dispose()
If mSplash.IsHandleCreated Then
mSplash.Invoke(New MethodInvoker(AddressOf stopThread))
End If
End Sub
Private Sub stopThread()
mSplash.Close()
End Sub
Private Sub workerThread()
mSplash = Form_WaitGif
mSplash.StartPosition = FormStartPosition.Manual
mSplash.Location = mLocation
mSplash.TopMost = True
Application.Run(mSplash)
End Sub
End Class
Public Class Form_WaitGif
Private Sub Form_WaitGif_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Me.CenterToScreen()
LoadDataFormAbort = 0
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
t.Source.Cancel() 'Not recognized
Me.Dispose() 'Is this needed when killing large classes to free up memory without forced GC?
Label1.Left = 100
Label1.Text = "Please wait - Terminating data loading (may take a while for large files...)"
End Sub
Public Overloads Sub Dispose() Implements IDisposable.Dispose
'Dispose(True)
GC.SuppressFinalize(Me)
End Sub
End Class
In order to keep responsiveness in the UI, I use a separate thread to execute various process, for example some FTP download.
Private Sub Button11_Click(sender As Object, e As EventArgs) Handles Button11.Click
Dim ThreadResync As System.Threading.Thread
ThreadResync = New System.Threading.Thread(AddressOf Bodacc_ResyncFTP)
ThreadResync.Start()
End Sub
Sub Bodacc_ResyncFTP()
Dim MyBodacc As bodacc_data = New bodacc_data
MyBodacc.Label_Status = Form1.Label1
MyBodacc.ResyncFTP()
End Sub
A way to update the UI with threading is the Delegate thingy, so in the bodacc_data I had to
Public Class bodacc_data
......
Delegate Sub UpdateLabelDelg(text As String, ThisLabel As Label)
Public Delegate_label As UpdateLabelDelg = New UpdateLabelDelg(AddressOf set_label)
Public Label_Status = Label
......
Sub set_label(stext As String, ThisLabel As Label)
ThisLabel.Text = stext
End Sub
.....
Sub ResyncFTP()
//says hello
If Label_Status.InvokeRequired = True Then
Label_Status.Invoke(Delegate_label, New Object() {"Working...", Label_Status})
Else
Label_Status.Text = "Working..."
End If
//do stuff
End Sub
End Class
It works like a charm. But I have many class doing more or less the same (disk update, database update, FTP update) and having to copy/past all the delegate / external label declaration / mini sub / invoke sound silly.
So I created a class to handle those UI update / delegate in order to have a quick access
Public Class Form_UI
Delegate Sub UpdateLabelDelg(text As String, ThisLabel As Label)
Public Delegate_label As UpdateLabelDelg = New UpdateLabelDelg(AddressOf set_label)
Private Labels(2) As Label
Sub New()
Labels(0) = Form1.Label1
Labels(1) = Form1.Label2
Labels(2) = Form1.Label3
End Sub
Sub set_label(stext As String, ThisLabel As Label)
ThisLabel.Text = stext
End Sub
Public Sub ChangeLabel(ByVal LabelNum As Integer, nText As String)
LabelNum = LabelNum - 1
If Labels(LabelNum).InvokeRequired Then
Labels(LabelNum).Invoke(Delegate_label, New Object() {nText, Labels(LabelNum)})
Else
Labels(LabelNum).Text = nText
Labels(LabelNum).Update()
End If
End Sub
End Class
So, now in the revamped bodacc_data and all others processing class I have only :
Public Class bodacc_data
......
Private MyUI as Form_UI
.....
Sub New()
MyUI = New Form_UI()
End Sub
Sub ResyncFTP()
//says hello
MyUI.ChangeLabel(1, "Working...")
//do stuff
End Sub
End Class
Question Why is MyUI.ChangeLabel not updating when the ResyncFTP is called in a thread, but works if called in the main thread (As in the code sample below)
Private Sub Button11_Click(sender As Object, e As EventArgs) Handles Button11.Click
Dim MyBodacc As bodacc_data = New bodacc_data
MyBodacc.ResyncFTP()
End Sub
Note that there is no error thrown. The notable weirdness is that <Form_UI>.ChangeLabel() never goes the .Invoke route but the normal update route. I strongly suspect a scope issue or insight issue.
When you create a windows forms app you set up a UI thread that is meant to be the owner of all the UI. The UI thread contains the message pump that is used to update all of the UI.
But what you're doing in Button11_Click is creating a new thread that goes and calls Dim MyBodacc As bodacc_data = New bodacc_data which, in turn, calls MyUI = New Form_UI().
You are creating a form on a non-UI thread. There is no message pump and therefore the UI doesn't update.
I'm looking at a console app for vb.net. I'm trying to get a worker thread to raise an event to the main thread to display data on the screen (the word "HIT" everytime the worker thread completes a cycle). My code is below.
I'm not sure why but the main thread's Private Sub CounterClass_GivingUpdate() Handles _counter.AboutToDistributeNewupdate isn't executing.
Imports System.Threading
Module Module1
Private WithEvents _counter As CounterClass
Private trd As Thread
Sub Main()
While True
Dim s As String = Console.ReadLine()
Dim started As Boolean
Select Case s
Case "status"
WriteStatusToConsole("You typed status")
Case "startcounter"
If started = False Then
starttheThread()
started = True
WriteStatusToConsole("You Have Started The Timer")
Else
WriteStatusToConsole("YOU HAVE ALREADY STARTED THE TIMER!!!")
End If
End Select
End While
End Sub
Private Sub CounterClass_GivingUpdate() Handles _counter.AboutToDistributeNewupdate
WriteStatusToConsole("Hit")
End Sub
Private Sub starttheThread()
Dim c As New CounterClass
trd = New Thread(AddressOf c.startProcess)
trd.Start()
End Sub
Sub WriteStatusToConsole(ByVal stringToDisplay As String)
Console.WriteLine(stringToDisplay)
End Sub
End Module
Public Class CounterClass
Public Event AboutToDistributeNewupdate()
Public Sub sendStatusUpdateEvent(ByVal updatestatus As String)
RaiseEvent AboutToDistributeNewupdate()
End Sub
Public Sub startProcess()
Dim i As Int64
Do
Thread.Sleep(1000)
i = i + 1
sendStatusUpdateEvent(i.ToString)
Loop
End Sub
End Class
Your CounterClass_GivingUpdate() only handles the _counter variable's event (the variable that you do not use!). Every time you declare a new CounterClass it has its own instance of the event that it raises.
You know have two options:
Option 1
Subscribe to the event for each new CounterClass instance you create. Meaning you must use the AddHandler statement every time you create a new instance of your class:
Private Sub starttheThread()
Dim c As New CounterClass
AddHandler c.AboutToDistributeNewupdate, AddressOf CounterClass_GivingUpdate
trd = New Thread(AddressOf c.startProcess)
trd.Start()
End Sub
Option 2
Mark the event as Shared to make it available without needing to create an instance of the class. For this you must also change how you subscribe to the event, by subscribing to it in your method Main():
Sub Main()
AddHandler CounterClass.AboutToDistributeNewupdate, AddressOf CounterClass_GivingUpdate
...the rest of your code...
End Sub
Private Sub CounterClass_GivingUpdate() 'No "Handles"-statement here.
WriteStatusToConsole("Hit")
End Sub
Public Class CounterClass
Public Shared Event AboutToDistributeNewupdate() 'Added the "Shared" keyword.
...the rest of your code...
End Class
I've defined a SerialPort object as the following:
Public WithEvents SerialComm As New System.IO.Ports.SerialPort
SerialComm is setup and opened in the object constructor and closed when the object is disposed. My handler signature is as follows:
Private Sub OnComm(sender as Object, e as SerialDataReceivedEventArgs) Handles SerialComm.DataReceived
I'm trying to get a DataReceived event to fire from HyperTerminal. After sending some data, I can set a breakpoint and check the value of SerialComm.BytesToRead and see that it has updated to the proper number of bytes.
I have confirmed that the SerialPort is open and is receiving data, but I can't get the event to fire.
I've also tried manually wiring up the event (after removing the WithEvents definition) using AddHandler, but I was still unable to get the event to trigger.
What am I missing?
Update:
This is the class that I'm having trouble with:
Imports System.IO.Ports
Public Class CopyCat
Implements IDisposable
Private RxString As String
Private LastReceiveTime As DateTime
Public WithEvents SerialComm As New SerialPort
Public Property Timeout As TimeSpan
Public Sub New(commPort As String, timeout As TimeSpan)
Me.Timeout = timeout
Enable(commPort)
End Sub
Public Sub New(commPort As String)
Me.New(commPort, TimeSpan.FromMilliseconds(1000))
End Sub
Public Sub Enable()
CommUtilities.SetupComm(SerialComm, commPort, 115200, 8, Parity.Odd, StopBits.One, Handshake.None, System.Text.Encoding.Default)
End Sub
Public Sub Disable()
SerialComm.Close()
End Sub
Private Sub OnComm(sender As Object, e As SerialDataReceivedEventArgs) Handles SerialComm.DataReceived
If(DateTime.Now - LastReceivedTime > Timeout) Then RxString = ""
Do While(SerialComm.BytesToRead > 0)
Dim readChar As String
Dim termChar As Char = Chr(RxString.ToByteList().XorAll())
readChar = SerialComm.ReadChar
RxString &= readChar
if (readChar = termChar) Then
SerialComm.Write((From item In GetResponse(RxString).Build()
Select item.Data).ToRawString)
RxString = ""
End If
Loop
End Sub
Public Function GetResponse(commandString As String) As MessageResponse
Dim response As MessageResponse = MessageResponse.GetMessageResponseFromByteList(commandString.ToByteList())
if (response.GetType = GetType(GetStatusResponse)) Then
response.DataBytes(8).Data = Math.Floor(Rnd() * 255)
response.DataBytes(9).Data = Math.Floor(Rnd() * 255)
End If
Return response
End Function
Private disposedValue as Boolean
Protected Overridable Sub Dispose(disposing As Boolean)
If Not Me.disposedValue Then
If disposing Then
SerialComm.Dispose()
End If
End If
Me.disposedValue = True
End Sub
Public Sub Dispose() Implements IDisposable.Dispose
Dispose(True)
GC.SuppressFinalize(Me)
End Sub
End Class
I haven't really done much with threads before and I'm having a problem updating a label and closing a form.
When debugging, the CloseDialog() sub is definitely running in the main thread so I don't understand why it's not closing. There are no loops or anything else running on the form to keep it open. I'm also having a problem updating the text on a label with information passed from another thread in real time.
The AddOUToTreeView sub gets invoked and works fine, but the subs from frmStatus never do anything.
frmMain:
Private WithEvents bkg As New ADSearcher
Private Sub startSearch_Click(ByVal sender As Object, ByVal e As EventArgs) Handles startSearch.Click
With bkg
.RootPath = "LDAP://domain.com"
.FilterString = "(objectCategory=organizationalUnit)"
If Not integratedAuth Then
.UserID = "user"
.Password = "pass"
End If
.PageSize = 5
.PropertiesToLoad = New String() {"cn", "name", "distinguishedName", "objectCategory"}
Dim search As New Threading.Thread(AddressOf .StartSearch)
search.Start()
Dim statusDialog As frmStatus = New frmStatus
statusDialog.Show() 'I want to use ShowDialog() but removed it when trouble shooting
End With
End Sub
Private Delegate Sub displayStatus(ByVal entriesFound As Integer)
Private Sub bkg_ResultFound(ByVal ousFound As Integer) Handles bkg.ResultFound
Dim display As New displayStatus(AddressOf frmStatus.UpdateOUSearcherStatus)
Me.Invoke(display, New Object() {ousFound})
End Sub
Private Delegate Sub displayResult(ByVal node As TreeNode)
Private Delegate Sub closeStatusDialog()
Private Sub bkg_SearchCompleted(ByVal ouNodes As TreeNode) Handles bkg.SearchCompleted
Dim display As New displayResult(AddressOf AddOUToTreeView)
Me.Invoke(display, New Object() {ouNodes})
Dim closeStatus As New closeStatusDialog(AddressOf frmStatus.CloseDialog)
Me.Invoke(closeStatus)
End Sub
Private Sub AddOUToTreeView(ByVal node As TreeNode)
tvOU.Nodes.Add(node)
tvOU.TopNode.Expand()
End Sub
frmStatus (Both of these functions do nothing):
Public Sub CloseDialog()
'Me.DialogResult = Windows.Forms.DialogResult.OK
Me.Close()
'Me.Dispose()
End Sub
Public Sub UpdateOUSearcherStatus(ByVal entriesFound As Integer)
'lblOUsFound.Text = Format("{0} Organizational Units Found", ousFound)
lblOUsFound.Text = entriesFound.ToString
End Sub
In my ADSearcher class I have:
Public Event ResultFound(ByVal ousFound As Integer)
Public Event SearchCompleted(ByVal ouNodes As TreeNode)
and raise the events with:
RaiseEvent ResultFound(resultCount)
'and
RaiseEvent SearchCompleted(rootNode)