Have Background Thread Handle Events?
Apr 7, 2011
I am in the planning stages for developing a VB.Net class (let's call it OpDAq) that is to obtain data via an API provided by a COM object (AxInterop.TWSLib) that makes requests to an Internet server. The API provides data via events. Class OpDAq should do its work on a separate thread; it takes several seconds (sometimes up to ~10) to collect the desired data. One should be able to create several instances of OpDAq in order to collect data in parallel. The class would be given a reference to the TWSLib object when its constructor is called, as well as several parameters. There needs to be a way for the class to provide results, preferably in the form of a generic list.
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Apr 17, 2009
I need an application in background that handles key events in other applications. Really i only need to know if user press F7 key, and after call some functions. I try with
[Code]...
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Aug 27, 2011
I am trying to call a method that started on a background thread on the UI thread calling BeginInvoke and passing in a delegate as follows:
Dispatcher.BeginInvoke(Function() UpdateApplicationDataUI())
to call this method:
Private Sub UpdateApplicationDataUI()
...
End Sub
However, I get an error in the call to BeginInvoke (the UpdateApplicationDataUI portion of the delegate is stating "Expression does not produce a value").
Me.Dispatcher.BeginInvoke(Function() New Action(AddressOf UpdateApplicationDataUI))
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Dec 4, 2008
A non-UI thread in my prog needs to obtain data from a UI listview control. To prevent cross-thread errors I use the following, but it freezes the prog (probably because the "Else" part is never called).What am I doing wrong?
[Code]...
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Jul 19, 2010
Is it possible in VB.NET to easily write an event handler that will handle every event that fires? I'm wondering if one could make a logging system using something like this.I'm wanting to do something like (in pseudocode):
Public Sub eventHandledEvent(ByVal sender As Object, ByVal e As EventArgs)
File.Write(sender.EventName)
End Sub
I realize it would be slow, but it wouldn't be for a production system, only as a development tool.
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Sep 2, 2011
I'm trying to move some code into some class files to clean up my code. One area I'm having trouble with is reporting progress for events between the object performing the task and a progress bar. I guess the event functions have to be placed in the new class but they also need to update the progress bar on the calling form? Can the classobject return updates in place of the event handlers?
[Code]...
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Nov 13, 2009
i have the ComClassSearchCustomers class and interface IComClassSearchCustomersat .net which used to create a tlb file. The class raise an event inside new. After that i have a vb6 form Form1 which catch the event , but it never see the event.
[Code]...
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Aug 1, 2011
I have the below code. When I execute this code, the handle is different between the Load event and the Shown event. I thought the handle was static for an instance of a window. What could cause the handle to change? The only other thing the form is doing is setting itself to invisible and setting the ShowInTaskbar = False in the Activated event.
[Code]...
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Aug 9, 2010
I have multiple textboxes which I want them to perform the same thing upon clicking them. By default I can use the handles textbox1.click for 1 single textbox but I am not sure how to do handle multiples of them. Of course I can write a handler for every single textbox but I have about 50.
Sub TextBox1_click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.Click
If Button9.Text = "Make Changes" Then
If TextBox2.Text <> "" Then
Frm_Cine1.Show()
[Code] .....
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Dec 17, 2010
From within the same form is this possible? I could eliminate a ton of code if this were possible.
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Jan 15, 2009
I created a Class which inherits Combobox and the listview is added . Now what I need is once the user click listview, the listview has to close and the clicked item has to added with combobox text. simply can say combobox1.text = listview.item(0).textFor closing & displaying the listview I need to handle the events. For
My Codings :========Public Class Combu_lstviewInherits ComboBoxPrivate treeViewHost As ToolStripControlHostPrivate Shadows dropdown As ToolStripDropDownPublic mylistview As New ListView
Public Sub New()mylistview.BorderStyle = BorderStyle.Nonemylistview.View = View.Detailsmylistview.HeaderStyle =
[code].....
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Apr 21, 2010
Is there any limit to the no. of handles assigned to an routine. Well actually my form form has about 80 controls and when ever the user press the enter key, focus must be to the next control. so can I handle all the 80 keydown events in one routine, or is there an better way.
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Jan 22, 2011
I've got a form that acts as a progress report for a long running operation, it has a listview on it (which I might be replacing with a DGV soon) that gets updated with progress updates from a background thread that is doing all the work. The method running on the background thread raises events that the form then handles and adds the string passed in to this event to the listview. The method running on the background thread raises progress update events several times a second and for each of these updates the event handler on the form must invoke a method on the UI thread to actually add the item to the listview.
This works fine on my test PC (which has a quad core CPU and 8 GB of RAM) but others have reported that after a while the form goes to the Not Responding state so I'm assuming all of these updates on the UI thread are being requested too often for it to be able to process them all as well as user input.So I'm looking for a better solution and have come up with the following:When the background thread raises these progress updated events, instead of them being added to the listview instantly I add them to a Queue(Of String). Then every second the form would check this queue and remove any items currently in it and add them to the listview - using a Queue(Of T) instead of a List(Of T) should guarantee they come out in the correct order. Both of these operations (adding to the queue and reading/removing from it) would be done under a SyncLock block that would lock on the same object to avoid both threads trying to work with the queue at the same time, so there would still be some contention but I'm hoping it would mean the UI thread only gets busy once a second instead of potentially roughly 30 times a second as it is doing now.Does that sound like a good plan? Can anyone think of a better way of handling this?
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Jun 22, 2009
I have a number of user control dynamically added to a page, and user interaction with these dynamically added user controls need to be handled by the control's parent. Is this what is referred to as "event bubbling"?How do I do that in VB?
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Jul 14, 2010
I am attempting to share a sub menu among several different parts of an application so that it is consistent (not wanting to copy/paste.) I thought it would be simple. I am doing something like this:
[Code]...
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Jan 10, 2012
I have created a PictureBox array to hold 104 playing cards that are all visible at the same time.I did this with this line in the declarations:Shared Card(104) As PictureBox
And with these lines in the Form_Load module:
For I% = 1 To 104
Card(I%) = New PictureBox
Card(I%).Name = String.Format("Card{0}", I%.ToString)
Card(I%).Size = New Size(71, 96)
[Code]...
I have been successful in creating the array, positioning each and entering the images for all 104 PictureBoxes, but now I want to add code for the event "MouseDown.I copied the code for this event from my VB3 program and VB10 automatically updated the list of parameters, but nothing has linked the objects (Card) to the code.
I have tried to append "Handles Card.MouseDown" as well as several variations with brackets to indicate that it is an array.Auto-complete doesn't include "Card" as an option, and of course, since the array was never an object added to the form design, I can't create the empty module from there.
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Feb 22, 2010
if I wanted the button onclick event in a different class how would I declare it?
when I refer back to the form it says I need to declare with events..
Private Sub btnAddToLaneFilter_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Dispatch.btnAddToLaneFilter.Click
If Me.txtCriteria.Text = "" Then
[Code]....
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Sep 7, 2010
I need to handle events that are thrown by Internet Explorer 8. I am able to handle events associated with the first tab that is created when IE8 launches, but I am unable to handle events if the user creates a new tab or opens a new window. I need to handle events of all tabs (and preferably all new windows as well) that are created by the instance of IE8 that is launched by my application.
[Code]...
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Apr 24, 2010
I want to handle the events of my serial input buffer. I've seen the following article:
[URL]
My programming skills are not really that great so I've got a question:How can I trigger a sub (for example: ArduinoSerialInput) as soon as this event is handled?
Code:
Public Delegate Sub SerialDataReceivedEventHandler(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
Dim SerialBufferIn As SerialDataReceivedEventHandler = AddressOf ArduinoSerialInput
Public Sub ArduinoSerialInput()
MsgBox("test")
End Sub
I use a piece of hardware to send data to my COM port, but nothing happens.
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Apr 7, 2011
I'm trying to use a asynchronous UDP-Port to recieve data on a form.I manage to receive one message at a time(for each click of btnReadData), however if I do this receive in a loop (in order to continously receive new messages), my form seems to be locked.What am I doing wrong?
Public Class FPR2DIS
Delegate Sub dDataReceived(ByVal Data As String)
Dim UDPWorker As New Worker
[code].....
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Jan 30, 2012
I want to create an object like the shape which is shown in the below picture. This picture is divided into different zones. I want to know how can I handle different events by clicking on different zones. For instance when the user click on zone 1 something is activated and when the user click on zone 2 another event is called.
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Sep 20, 2010
Am on creation of touch screen UI system.And am generating button for selecting products
Under certain category.
--> array of button creating dynamically And placing in TABPAGE when user selects Tab for category. The button will be created with the name of products, Under the category selected.
{
'the way am creating controls.
mybutton(j) = new button()
mybutton(j).top = 100
}
How can i get the Click event of those buttons-( in the array)....??
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Jun 20, 2011
I have the user control that is loaded dynamically. When the user save the data by clicking on the Save button, a raise event is passed.
Public Sub RaiseCloseEvent(ByVal sender As Object, ByVal e As System.EventArgs)
RaiseEvent Close(sender, e)
Debug.Print(String.Format("The control {{0}} was closed by {{1}}.", Me.Name, sender.ToString))
End Sub
In the save button I have called the RaiseCloseEvent as follows:
RaiseCloseEvent(sender, e)
Now, how can I close the user control form? Any Idea? I have used VB.Net language.
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Jul 28, 2010
I've been thinking about my options when it comes to events in vb.net.What I'd like to do is to track events that are fired in an application without explicitly declaring them with 'handles' sub. Here is a pseudo-[code]....
Yeah I know, not quite working, but is there any way of implementing something like this in vb.net? My end game is really to be able to monitor events fired in many objects from another object, isn't there a more maintainable way to do that then to add a special sub in each object that handles the event that I want to catch? I need some way to let one object handle events fired in other objects without a special sub, the AddHandler goes a long way, but I can't really use that dynamically like so:[code]....
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Jul 20, 2009
I am trying to put a new face on an old C program. The C program is, of course, unmanaged code, designed smartly to separate the number crunching and the interface, and the interface I'm trying to replace is X windowing. The graphics part is where it gets a little hairy, because the C is going to need to continue to draw in my new interface, based on the data the program produces. Even if I want to duplicate that data in .NET so that the .NET side can handle all of the drawing, the fact remains I'm going to need to operate on the graphics window in some fashion from C.
I gather that handles have a lot to do with the bare Win32 graphic operations. Is such a similar handle provided to, say, a PictureBox element in .NET? And if so, is it the kind of handle I can use in the unmanaged code without an issue?
I have tried and tried and tried to google for the solution for weeks now, and all I come up with are either C++ solutions (using object-oriented GDI+) or some sort of extension to the C language.
Alternatively, is there a way I can have .NET create a handle specifically for this purpose of having C draw it?
To sum it up, I am using Visual Basic .NET 2008 and a C DLL (also compiled in VS2008), so far in the little testing I've done, I've been able to marshal complex structures to and fro, but I am not sure how exactly I'd let C do any drawing on the .NET form, if that was even possible.
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Mar 11, 2011
I am in need of adding arr of type label at run-time. I am making a program which will retrieve employee name from database in different label. On clicking each employee name (label) it will display all the information about that employee in a msgbox. I use the following code to create the label. Since the number of labels is not fixed I have used an array.
dim withevents lblArr() as Label 'declared in the class
In the subroutine(Form load):
for i as integer=0 to NoofEmployee-1
redim lblArr(NoofEmployee-1)
lblArr(i)=new Label
' I assigned all the necessary property like size location etc..
me.controls.add(lblArr(i))
next
I declared another subroutine:
private sub MyClick(sender as Object,e as EventArgs) **handles lblArr(0).click**
MsgBox("Hello")
end sub
The code doesn't compile since a subroutine doesn't.
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Apr 25, 2010
I want to handle the events of my serial input buffer. [code] My programming skills are not really that great so I've got a question:How can I trigger a sub (for example: ArduinoSerialInput) as soon as this event is handled? I've tried some code but without success, that's why I decided to post on the forum [code] I use a piece of hardware to send data to my COM port, but nothing happens.
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Sep 14, 2011
I've a little program that has got tabControl with 2 tabs - "results" and "log". My idea was that when an error occurs the tab will switch automatically on tbLog to show what the problem was. Most arguably the problem is in threading. This is the code that..I use:
Dim thread As New Thread(AddressOf ExecuteQuery)
thread.Start()
ExecuteQuery executes the query and I'm making an error deliberately to see if I'll be automatically switched to the log tab which is in Try-EndTry procedure:
tbGrid.SelectedTab = tbGrid.TabPages(1)
The program indeed switches to tabLog (which is number 1) but I don't see any controls on it (txtLog), then when I'm trying to switch tabs a couple of times I get "Error creating window handle in a thread". I read other forum threads about it where people as how many controls do they have in their programs but my program does not exceed 70 controls on a form.
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Feb 5, 2011
I have an application which runs two threads.
- One thread is the main thread while the other one is to monitor the main thread.
- The errors are written to a custom event log
- There is an event handler to handle the event logs
- When an event occurs I want to create a new thread and update the event to a sql table (pseudo code)
- Also in case their are number of errors/events
how should I handle them (pseudo code)
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Sep 23, 2011
I have a vb.net application in which there is a main form. There are around 10 classes each having their own functionalities like tcpactions, fileactions, serialport actions etc. The user interacts with the main form and does certain actions which will invoke the methods in these classes. Now I have a notifications textarea in the mainform and i want to show the current action being performed in those classes and their results in the notifications area.
for example when a user clicks a "Start Process" Button in the form i invoke the method "launchprocess" in a class "ProcessActions". Now this method tries to launch about 7 different process and after launching it sends notification such as "process 1 launched" or if it fails it sends notifications such as "process 1 launch failed".
I currently use event handlers and use them to show notifications but with the amount of events i have to handle it is getting cumbersome and i might have to add even more classes in the future. So is there a better way of handling notifications from other classes.
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