I am creating a very simple state machine class library project in vb.net.
This has only 3 states - CreateApplication, ProcessApplication and CompleteApplication.
I have an interface created in the same project.I am invoking it from a web application by calling ApplicationService.CreateApplication(obj of ApplicationDetail)
<ExternalDataExchange()> _
Public Interface IApplicationService
Event ApplicationCreated As EventHandler(Of ApplicationDetailEventArgs)
Event ApplicationProcessed As EventHandler(Of ApplicationDetailEventArgs)
End Interface
I also have its implementation in ApplicationService.vb
Public Class ApplicationService
Implements IApplicationService
Public Event ApplicationCreated(ByVal sender As Object, ByVal e As ApplicationDetailEventArgs) Implements IApplicationService.ApplicationCreated
Public Event ApplicationProcessed(ByVal sender As Object, ByVal e As ApplicationDetailEventArgs) Implements IApplicationService.ApplicationProcessed
Public Shared Sub CreateApplication(ByVal objApplicationDetail As ApplicationDetail)
Using workflowRuntime As New WorkflowRuntime()
AddHandler workflowRuntime.WorkflowCompleted, AddressOf OnWorkflowCompleted
AddHandler workflowRuntime.WorkflowTerminated, AddressOf OnWorkflowTerminated
Dim workflowInstance As WorkflowInstance
workflowInstance = workflowRuntime.CreateWorkflow(GetType(Workflow1))
workflowInstance.Start()
End Using
'Code to create application
End Sub
Shared Sub OnWorkflowCompleted(ByVal sender As Object, ByVal e As WorkflowCompletedEventArgs)
End Sub
Shared Sub OnWorkflowTerminated(ByVal sender As Object, ByVal e As WorkflowTerminatedEventArgs)
End Sub
End Class
My issueis that, when I try to run it I am getting the value of workflowInstance . InstanceId as Empty.
I have been trying to fix this since the last 2 days.
Can someone please help.
Thanks in advance!
Well..I was able to figure out what the problem was.
It has nothing to do with workflow. It is a bug in Visual Studio(2005 and 2008). When you debug in VB.Net, the value of a Guid shows up as empty, but if you use Guid.ToString..it works fine. This does work correctly in C#.
Related
First of all, this is my very first question in this community. Please give me some advice if I did it in the wrong way.
I need a little bit help. I am actually working on a BMEcat class library, BMEcat is a data exchange format for electronic catalogs. Anything works fine, but I realized that there is a memory problem while processing very large files. Because of this, I want to send an event for any processed article/product instead of creating a huge structure in memory.
This is the point where my problem begins.
I have a class CTRANSACTION, from which the classes CT_NEW_CATALOG, CT_UPDATE_PRODUCTS and CT_UPDATE_PRICES are derived.
In the base class CTRANSACTION there is an event defined:
Public Event Transaction_OnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
The class CBMECAT has the variable
Public WithEvents TRANSACTION As CTRANSACTION
and the event handler
Private Sub TRANSACTION_Transaction_OnNewArticle(sender As Object, e As ArticleEventArgs) Handles TRANSACTION.Transaction_OnNewArticle
'...
End Sub
Because I cannot send the event Transaction_OnNewArticle from the derived CT_NEW_CATALOG class I let it call the TransactionEventOnNewArticle method instead, which is defined in CTRANSACTION. TransactionEventOnNewArticle then calls RaiseEvent Transaction_OnNewArticle.
Everything works wonderful, but the event Transaction_OnNewArticle is not fired. Is there a way to fix it?
Public MustInherit Class CTRANSACTION
Inherits CBMECAT_NODE
Public Event Transaction_OnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
Public Sub TransactionEventOnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
RaiseEvent Transaction_OnNewArticle(sender, e)
End Sub
Public Class CT_NEW_CATALOG
Inherits CTRANSACTION
Public Overrides Sub EventOnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
TransactionEventOnNewArticle(sender, e)
End Sub
Public Class CBMECAT
Inherits CBMECAT_NODE
Public WithEvents TRANSACTION As CTRANSACTION
Private Sub TRANSACTION_Transaction_OnNewArticle(sender As Object, e As ArticleEventArgs) Handles TRANSACTION.Transaction_OnNewArticle
'THIS method is never called - why?
End Sub
End Class
UPDATE
Public Class CBMECAT_ELEMENT
Public Overridable Sub EventOnNewArticle(ByVal sender As Object, ByVal e As ArticleEventArgs)
End Sub
'Please notice that CBMECAT_ELEMENT is the base class of EVERY other class in the library.
'There is a class CBMECAT_NODE, which represents every node of the BMEcat XML structure and is derived from CBMECAT_ELEMENT.
'In CBMECAT_NODE is EventOnNewArticle called whenever an article is processed;
Public Class CBMECAT_NODE
Inherits CBMECAT_ELEMENT
Public Overridable Function CreateChildNode(ByRef Nodename As String, Optional ByRef Parent As CBMECAT_NODE = Nothing) As CBMECAT_ELEMENT
Select Case Nodename
[..]
Case ELEMENT_ARTICLE
CreateChildNode = New CARTICLE(Parent)
Dim e As New ArticleEventArgs With
{
.ARTICLE = CreateChildNode
}
EventOnNewArticle(Me, e)
[..]
UPDATE
Public Class CARTICLE
Inherits CBMECAT_NODE
Public Sub New(ByRef Father As CBMECAT_NODE)
[..]
Public Overrides Sub Read()
[..]
Public Overrides Sub Write()
[..]
Public Overrides Sub Validate()
[..]
UPDATE
Calling sequence:
CBMECAT_NODE.CreateChildNode calls CT_NEW_CATALOG.EventOnNewArticle <- OK
CT_NEW_CATALOG.EventOnNewArticle calls CTRANSACTION.TransactionEventOnNewArticle <- OK
CTRANSACTION.TransactionEventOnNewArticle fires Event Transaction_OnNewArticle
but this event is not received by the event handlier in CBMECAT
If I fire the event manually from a method in CTRANSACTION the event IS received by the event handler.
I also experimentet with AddHandler/RemoveHandler, but this also did not work.
Thank you, Visual Vincent, for helping me to focus the problem and to solve it. In deed it was "a little bit" complicated.
Class CBMECAT had the following read method:
Public Overrides Sub Read()
MyBase.Read()
GetContent(HEADER, ELEMENT_HEADER)
Select Case TransactionType
Case TransactionTypes.T_NEW_CATALOG
GetContent(TRANSACTION, ELEMENT_T_NEW_CATALOG)
Case TransactionTypes.T_UPDATE_PRICES
GetContent(TRANSACTION, ELEMENT_T_UPDATE_PRICES)
Case TransactionTypes.T_UPDATE_PRODUCTS
GetContent(TRANSACTION, ELEMENT_T_UPDATE_PRODUCTS)
Case Else
ReportError(ERROR_BMECAT_UNKNOWN_TRANSACTION_TYPE)
End Select
Validate()
End Sub
MyBase.Read reads the complete XML file and while reading it, the events should be fired. But at this moment the variable TRANSACTION is not assigned by it´s value. This is done by calling GetContent after the reading process has finished.
I have changed to:
TRANSACTION = New CT_NEW_CATALOG
TRANSACTION.Read()
Now all events are fired as expected.
I will remove TransactionEventOnNewArticle() from CBMECAT_ELEMENT. Thanks again, Vincent, for your suggestion. :-)
When the form loads, it stars a thread to find all the computers in the network with the use of a library, then for each computer it creates a class which is stored in a list, that class handles the TCP communication between the computer and the remote end, when data is received i want to show it on my form
The code looks something like this
Public Class FormHub
Public Sub ChangeUI (ByVal Text as String)
.....
End Sub
Private Sub FormHub_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim thr As New Thread(AddressOf FindComputers)
thr.Start()
End Sub
Sub FindComputers()
For Each Computer As String In APINetworkItems.GetAllComputersInDomain
For Each Address As IPAddress In Dns.GetHostEntry(Computer).AddressList
If Address.AddressFamily = AddressFamily.InterNetwork Then
Dim handler As New RemoteEnd
handler.Connect(New IPEndPoint(Address, Port), Address, Computer)
ConnectionList.Add(handler)
End If
Next
Next
End Sub
Public Class RemoteEnd
Public Sub Connect(ByVal EndPoint As IPEndPoint, ByVal IP As IPAddress, ByVal Name As String)
.........
End Sub
Public Sub Receive()
....
<Here i want to call a sub on the Form>
End Sub
End Class
Googled it, nothing seems to work... what do i do?
This is the most common problem for people who are just starting to understand multi threading. Think about how WinForm controls interact with calling elements. They use events to signal to the outside world that something happened within them. You can do the same:
Public Class SomeForm
Private connectionsList As New List(Of RemoteEnd)
Public Property Port As Integer
Sub FindComputers()
For Each comp As String In APINetworkItems.GetAllComputersInDomain
For Each addr As IPAddress In Dns.GetHostEntry(comp).AddressList.Where(Function(a) a.AddressFamily = AddressFamily.InterNetwork)
Dim remote As New RemoteEnd
' Add a handler to handle the Connected event that the RemoteEnd class exposes, and then call its Connect sub.
' Note that we do not add the instance to the list yet, as it's not really connected yet (not as long as the RemoteEnd class
' hasn't raised the Connected event...)
AddHandler remote.Connected, AddressOf RemoteEnd_Connected
remote.Connect(New IPEndPoint(addr, Port), addr, comp)
Next
Next
End Sub
Private Sub RemoteEnd_Connected(ByVal sender As Object, ByVal e As EventArgs)
' When the form catches the event, it restores the reference to the instance that raised it, and
' add the instance to the list. Keep in mind that the event will be handled on the same thread it was raised!
' That means that if you want to display data in a form control, you need to invoke the form to make the change!
' Here we just add a reference to a list, so it doesn't matter.
Dim remote = DirectCast(sender, RemoteEnd)
connectionsList.Add(remote)
DoSomething(remote)
End Sub
Private Sub DoSomething(ByVal remote As RemoteEnd)
' ...
End Sub
End Class
Public Class RemoteEnd
Public Event Connected(ByVal sender As Object, ByVal e As EventArgs)
Public Sub Connect(ByVal EndPoint As IPEndPoint, ByVal IP As IPAddress, ByVal Name As String)
' To work efficiently, when this sub is called we need to start the asynchronous process and return immediately.
' When the connection is fully handled, we will raise the event and carry a reference to this instance to the form.
' Because QueueUserWorkItem only takes in one state object to pass parameters, we create a single object that
' contains all the information needed to connect and pass that.
Dim params = New ConnectionInfo(EndPoint, IP, Name)
ThreadPool.QueueUserWorkItem(New WaitCallback(AddressOf HandleConnectionAsync), params)
End Sub
Private Sub HandleConnectionAsync(ByVal connectionInfos As ConnectionInfo)
' ...
' Here we raise the Connected event for the outside world, carrying a reference to this instance,
' and possibly an instance derived from EventArgs. Here we return nothing.
RaiseEvent Connected(Me, Nothing)
End Sub
End Class
Public Class ConnectionInfo
Public Property EndPoint As IPEndPoint
Public Property IP As IPAddress
Public Property Name As String
Public Sub New(ByVal _ep As IPEndPoint, ByVal _ip As IPAddress, ByVal _name As String)
EndPoint = _ep
IP = _ip
Name = _name
End Sub
End Class
Your RemoteEnd class has no reason whatsoever to even be aware of the form, this is very important, because you want each class of yours to be loosely coupled to others. If a class depends on another, they both should be in the same assembly, but if not they should be separate, so that they can be reused elsewhere. If your form depends on your class, and your class depends on your form, it's called codependency, and it is very bad from an architectural point of view. It might work, but it will be hell to maintain.
As for your original question, once you are setup with the above code, you will notice that the code in the RemoteEnd_Connected handler is actually executed on the same thread that we created on the threadpool in the RemoteEnd class. That means that within that handler, you cannot play with UI controls, because they are on another thread. You need to ask the form to call the delegate with the parameters you need:
Private Delegate Sub SetTextDelegate(ByRef ctrl As Control, ByVal text As String)
Private delSetText As New SetTextDelegate(AddressOf SetText)
Private Sub SetText(ByRef ctrl As Control, ByVal text As String)
ctrl.Text = text
End Sub
Private Sub DoSomething()
If Me.InvokeRequired Then
Me.Invoke(delSetText, {SomeTextBox, "This is the text to set..."})
Else
SomeTextBox.Text = "This is the text to set..."
End If
End Sub
I am trying to call the function getTemp(value as integer) from my webservice service1. When I execute the code it gives an error saying that _value is nothing.
If I call the same function in a normal windowsforms project it runs perfectly.
Does anyone have a solution ?
See my code below (import statements omitted):
Dim _value As String
Private Sub Button_Click_1(sender As Object, e As RoutedEventArgs)
Dim client As New Service1Client
AddHandler client.GetTempCompleted, AddressOf getTempgotten
client.GetTempAsync(3)
MessageBox.Show(CStr(_value))
End Sub
Public Sub getTempgotten(sender As Object, e As GetTempCompletedEventArgs)
_value = CStr(e.Result)
End Sub
PS: I'm new to this forum, so forgive my mistakes.
Consider the following code, in a brand new WinForms .NET 4.0 application, with default settings:
Public Class Form1
Private Sub AAA()
Form1.AAA(Nothing) 'cannot refer to itself through its default instance; use 'Me' instead.
End Sub
Private Shared Sub AAA(str As String)
End Sub
End Class
I am getting this error:
{FORM_CLASS_NAME} cannot refer to itself through its default instance; use 'Me' instead.
I also get this warning at the same line:
Access of shared member, constant member, enum member or nested type through an instance; qualifying expression will not be evaluated.
Assuming default instance is meant here, it ends up in an infinite loop - VS suggests to change Me.AAA() to Form1.AAA(), and then back. AAA() works in both.
Converting Private Sub AAA() to Shared solves the error. It seems like from Microsoft's point of view, all overloads must be shared, if at least one is. Or you get this default instance confusion. Why?
To clarify, I do not want to use default instance here, just do a shared call.
If anyone encountered the same situation, please advise.
Creating a variable alias that has the same name as the type of the Form class is without a doubt the single most disastrous VB.NET problem. But it was necessary to give VB6 developers a fighting chance to move to VB.NET.
The workaround is to stop trying to be explicit about what method you want to call. This compiles fine and is unambiguous, at least in your snippet:
Private Sub AAA()
AAA(Nothing) '' fine
End Sub
If that really, really hurts then simply swapping the two methods removes the ambiguity:
Private Shared Sub AAA(str As String)
End Sub
Private Sub AAA()
Form1.AAA(Nothing) '' fine
End Sub
Can you get away with this? Your usage will be very similar Form1.AAA() vs. code.AAA().
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
code.AAA()
End Sub
Private Class code
Public Shared Sub AAA()
End Sub
End Class
End Class
EDIT
Given the new information in the OP - another solution to your issue may be to use optional parameters -- ie :
Private Shared Sub AAA(Optional ByVal str As String = Nothing)
Also - the resolution works out in the "right" way if you simply change the ordering of the declarations -- this avoids the compiler error:
Private Shared Sub AAA(ByVal str As String)
End Sub
Private Sub AAA()
Form1.AAA(Nothing)
End Sub
--
Keeping this below because it can be helpful in other circumstances
Perhaps your larger application did something like this - VB is full of messes like this you can get yourself into. This will compile but it will crash :
Public Class Form1
Private Shared Sub AAA()
Form1.Text = "this"
End Sub
Private Sub Label1_TextChanged(sender As System.Object, _
e As System.EventArgs) _
Handles Label1.TextChanged
Form1.AAA()
End Sub
End Class
Just the same, this actually is "fine" (I use the term loosely)...
Public Class Form1
Private Shared dont As Boolean = True
Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
Handles MyBase.Load
dont = False
End Sub
Private Shared Sub AAA()
If Not dont Then Form1.Text = "this"
End Sub
Private Sub Label1_TextChanged(sender As System.Object, _
e As System.EventArgs) _
Handles Label1.TextChanged
Form1.AAA()
End Sub
End Class
This is because the text changed handler will fire before Form1 completes loading (ie : during InitializeComponent()!) and will refer to the default instance which is not yet finished being created - so VB tries to create a new one for you so that you can call the shared method which spins you down the infinite loop.
Oddly, the Load handler is "fine" (again, loosely) to call Form1.AAA() in - as in your opening code - because the default instance (Form1 the instance of Form1 the Class) is finished creation at that point and another won't be created to satisfy the call. Any other code path, however, that starts in the shared call and ultimately ends up touching any instance data, no matter how torturous the path, will loop around and crash.
See also : Why is there a default instance of every form in VB.Net but not in C#?
Unclear what you are trying to accomplish overall. In the OP Form1.AAA should be just AAA.
Private Sub AAA()
AAA(Nothing)
End Sub
Private Sub AAA(str As String)
If str IsNot Nothing Then MsgBox(str) ' else ???
End Sub
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
AAA()
AAA("hello")
End Sub
Hey all i am trying to call a public sub within a class that resides within my form1 code:
Public Class Form1
Public Shared objItem As ListViewItem
Class Server
Private Shared Sub StringMessageReceived(ByVal sender As Object, ByVal e As StringMessageEventArgs)
MsgBox("Received message: " & Convert.ToString(e.Message))
'Form1.ListView1.Items.Add(Convert.ToString(e.Message))
Call Form1.writeToLV(Convert.ToString(e.Message))
End Sub
End Class
Public Sub writeToLV(ByRef theStuff As String)
MsgBox(theStuff)
objItem = ListView1.Items.Add(theStuff)
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
ListView1.View = View.Details
ListView1.Columns.Add("Response", CInt(500))
End Sub
End Class
It sends the value over just fine but when it gets to putting it into the listview it never does?
Any pointers?
David
The most likely explanation is that the form that has been opened on the screen is not the default instance referenced by Form1 in the Server class.
I think that you need to restructure your code somewhat: if you are only going to have one instance of Form1, explicitly create the form and keep a reference to it in a global variable (i.e. g_Form1) rather than relying on the VB-provided default instance (assuming you are ever only going to have 1 instance of the form.
If you can have more than 1 instance of Form1, I would convert your internal Server static class to an Interface and when a new form is created, have it register itself with whatever mechanism is calling Server.StringMessageReceived.