.NET Multithreading / Calling Invoke On A UI Control From A Class In A Separate Class File?
May 13, 2011
Example:
Two files - TestClass.vb, myForm.vb
TestClass.vb looks as follows:
Imports System.Threading
Public Class TestClass
Private myClassThread As New Thread(AddressOf StartMyClassThread)
[code]....
The result:Application runs, no errors or exceptions.Displayed is the listbox and the Start button.I press the start button and a msgbox says "Not Invoked" as expected and upon clicking OK to that msgbox "Start Button Pressed" is added to the Output listbox control.Immediately following that the msgbox pops up again and says "Not Invoked". I was expecting "Invoked" as a separate thread is trying to use the Output listbox control.Of course this results in the Output.Items.Add being attempted which results in no visible result as the thread is not allowed to directly update the UI control.
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Jan 24, 2012
I am making use of a serial port in a class. I am raising an event from that class to my form calling the class. Event contains data received... I wish to simply populate a textbox from the raised event.Now I am not specifically creating a seperate thread, but I get the normal crossthreading error when trying to update my textbox on the UI, so my assumption is that the serial port and its internal methods probably creates its own threads...Regardless, I am a bit confused as to how to properly implement an invoke, from my main form, pointing to the thread in the instantiated class...
Dim WithEvents tmpRS232 As New clsRS232
Private Sub but_txt_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles but_txt.Click
tmpRS232.Set_com_port("COM8", 38400)
[code]....
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Nov 16, 2011
Can we write all the control events in a seperate class file in different layer rather than in code-behind of web-page ?
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Feb 5, 2011
E.g. I have a class:
Namespace Common
Public Class AClass
Public Class BClass
[code]....
How can I use BClass without saying AClass.BClass, I've see some existing code using this format, but I can't find the setting.
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Nov 6, 2008
How can I move the following to a separate class for repeated use ? (the problem is that it uses response object)
' Download/View a given file
Protected
Sub downloadFile(ByVal sFile
As String)
[code]....
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Aug 5, 2011
I have a listbox in separate class like this [code]
[Code]...
How can I use that list box that I have created in that class on this form or I want to show that listbox on my form?
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Jul 21, 2010
control which will need to be reused in several forms in my program. It basically consists of several buttons in a panel. To start with, what I need to do is get the button values from the control into a text box on the first form. But I don't want to have a method calling the textbox directly from within the control, because then it won't be reusable in my other forms. Is there something I can do in VB like parentform.textbox.append for example, where you can generically call the methods of the form in which the control appears?
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Mar 16, 2010
I've got the following code:
[code]...
The problem is that, when I call the "SetStatusBarText" sub from another thread, InvokeRequired is True (as it should be), but then my threads stall on the Me.Invoke statement - pausing execution shows them all just sitting there, not actually invoking anything.
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Aug 5, 2010
<div sizcache="0" sizset="0">
i am having 2 class files a.vb and b.vb i have some public shared function in a.vb which i need to call in b.vb i have called it inthis way like the way i has called in normal .aspx pages in b.vb page i called the function of a.vb as
a.funcpwd("filedname") error BC30451: Name 'a' is not declared.
</div>
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Apr 22, 2010
Lets say I have a class like this in class1.vb:
Public Class my_class
Public Sub my_sub()
Dim myvar as String
myvar = 10
Session("myvar") = myvar
End Sub
End Class
Then I have a ASP.NET page with a code-behind file, default.aspx and default.aspx.vb and I want to call my_class. I'm doing the following, but it doesn't work:
[Code]...
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Jul 22, 2011
I have a class (see below)
Imports Microsoft.VisualBasic
Imports System.Data.SqlClient
Public Class ClientProfile
#Region "Variables"
[CODE]...
It is in the file ClientProfile I have placed in both App_Code and also App_Code/Models
In my code behind I have the following
[CODE]...
The last word, "ClientProfile" has the scary squiggly red line below it. It is not recognizing my class.Even the Intellisense is not picking up te class. Do I have to register the class file in any way?
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Mar 8, 2010
I've made an interface called ApprovalEvent in a separate file with the namespace myproject... I've also made a class called PurchaseOrder... it's also in the same namespace, just in a separate file. Whenever I try to make PurchaseOrder implement ApprovalEvent it always says that ApprovalEvent is undefined...
How can I make the class recognize that the interface exists but is in a different file?[code]...
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Jan 9, 2012
i would like to have a shared function in a separate class file to address the form location . but i dont know how can i get this to work. if i use this below code in my form its working . but i cannot move this to a class file.
Shared Sub Formlocation()
Me.StartPosition = FormStartPosition.Manual
Me.Location = Screen.GetWorkingArea(Me).Location
End Sub
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Mar 15, 2012
I have a VB program that writes a batch file to allow me to run a line of the following format:java <my class file> [options]I then run the batch file using the Shell() routine in VB.When I do this it says it cannot find <my class file>. However if I run the same batch file from a dos prompt it works.why it works in a dos prompt but not in the Shell function?
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Oct 9, 2009
I have written a class that handles my socket information, which means i need to raise events back to my form class using a delegate. But for some reason the following does not work: -
Public Class Form1
Private WithEvents objEthernet As Ethernet
Dim Eth As New Ethernet
[Code]....
Both of the Disconnected and connected events fire and are working from my socket thread but when i call "CallPassData" i get the following error "Invoke or BeginInvoke cannot be called on a control until the window handle has been created"
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Apr 13, 2009
I have a class with a background worker in it that does some tasks on a separate thread. I want to fire some events from the background worker thread to the 'main thread' of the class, so that when using this class your not obliged to go make invoke calls for every event handler your using.I'm at a loss of how to do this though. When having a similar problem in a form of usercontrol I always use Me.Invoke, but this method is not present in a class inheriting system.object.
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Jul 17, 2011
I am new to making events and I have read up on them to further my understanding of them, and I have come across a situation that I am stuck at. Currently I have a handful of classes (lets call them a childform) that are all inherited from a class that's a form (lets call it a parentform) with an event called UpdateData(). When these forms are created they are added into a hashtable of ParentForms then added into another form. I call on these forms through a method that returns the form from the hastable. [code]....
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Nov 21, 2009
I am searching for the Component Class. When I go to "Add New Item" ,in my project their is no Component Class Item in VS 2008. I would like to Drag and Drop control onto my new class and I can't see how to do this ?
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May 29, 2012
I want to invoke a method on a class that i have a reference to. The method that I want to call has a custom attributes. Currently I can find this attributes and call the property of my class Attribute.
is there a way to invoke that method ?
PS/ The project is written in vbnet, but I think the solution is the same in c#.
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Oct 2, 2009
I'm working on a class that has multithreading in it, this class has events that are being raised (raiseevent) in a new created threads within the class, for example:
[Code]...
Now when I load this example application an error is raised up saying that there is a cross thread error (Cross-Thread operation not valid control 'Text1' accessed from a thread other than the thread it was created on.) Now I don't want to handle this error within my form (editing the code in the form) what I want to do is to fix this problem within the class (I guess something with invoke?)
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Oct 13, 2010
We have a UI with a progressbar. I know how to invoke, safely, the control from which it was not created from a thread. there are threads being processed in a threadpool, all of which calls an "agent" (which is a notifier to raise an event back to the UI to then increase the progressbar). an "agent" is set as a property in a State object, which is then passed into a method which will be executed on the ThreadPool. so, I invoke on the UI the method to update the progressbar, but the bar does not seem to update at all (screen frozen) and it takes a very very long time for it to execute. without threading, no problem.
[Code]...
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Nov 1, 2011
I was using the following code within a class and creating an instance of that class from within my main form (Main.vb):Dim count As Integer = Main.DbDataSet.Accounts.CountThis was returning the count of accounts within my database.After changing the code so that I could run this in a background thread to save locking up the program, as more data is processed after this point, the count was returning 0 each time.
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Jun 4, 2011
Right now I have a Email class that has all the properties of an email to send it, and then a SendEmail function which takes those properties and uses them in the following
Public Function SendEmail()
'Exception handling
Try
[Code]....
The loop goes through each email in the array to process its email, however with the multithreaded function I cannot call
"EmailArray(i).ThreadSendBatchEmail()"
So how do I call an objects method when its on a different thread?
And I'm making it multithreaded so I can easily pause the process, and because the program freezes when the send() function is working, this would resolve that.
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Aug 9, 2011
so I used to mess around with C#, just a little. And someone had helped me make a class for Visual C# that was supposed to do the math parts for "internal structure" - which the program used for a part of its calculations and screen... Basically there were 2 options. Endo-Steel and Standard. The user would use a updownbox to determine weight of the machine and then internal structure was a % of that total. If it was standard then it was 10% of the overall weight, if it was Endo-Steel then it was 50% of standard (so 5% of total weight) rounded to next 0.5 (so .25 was .5, 1.25 was 1.5, 1.75 was 2.0, etc). I have the code for the C# class file for it, but want to make it in VB.
[Code]...
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Nov 22, 2009
Good evening folks, I'm building a program that is threaded. While I can get the thread to work no problem, I can not seem to add pages to my tabcontrol from the class I'm using. Any idea's on what I'm doing wrong?frmMain is loaded first. Then the idea is to load the other tabpages using a separate thread as they take awhile.[code]
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Jan 20, 2011
I am having following Projects
ClassLibrary1
Public Class Class1
Public Sub MyMethod()
[code].....
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Feb 11, 2011
I don't want my application's main form to be displayed when it opens; I just want the notifyicon control in it to show in the taskbar.This is the code I have been using:
Module:
Code:
Module mdlStartup
Public Sub Main()
[Code]...
The NotifyIcon control is in my frmMain. However, when I run my program I get mulitple instances of the Notify Icon being displayed. I even get two frmMains getting launched if I try clicking the other tray icon that has been made. I'm guessing this has to do with the New instance.If that's the problem, is there a way I can move the notifyicon control to some completely separate class?
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Mar 12, 2011
I have created a class for Socket reads so I can create sockets on command. Due to performing a socket read, the program will freeze waiting for incoming data due to being on a single thread. So I created a separate thread for the reading of the sock and attempt to invoke an event to prevent multi-threading errors.
But I am getting an error when trying to Invoke: "Invoke or BeginInvoke cannot be called on a control until the window handle has been created."
How can I fix this or is there a better way to read a sock without freezing the thread?
Class for Sockets:
Option Explicit On
Option Strict On
Imports System.Text
[CODE]...
Calling form code example:
Private WithEvents Socks As clsSock
Private Sub Sock_Connected(ByVal state As String) Handles Socks.Connected
MsgBox("Connected - " & state)
[CODE]...
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Dec 16, 2009
If Class X is within the scope of Class Y, is X a subclass of Y?If Class A is a sub Class of B, then is Class B considered a super class of A?if Class C inherits Class D is Class D a superclass or parent of Class C?if Class E extends Class F then we can consider Class E a child of F?if Class G inherits Class H and is within the scope of Class I then who is the parent of Class G? Classes that inherits Class J and classes that are within Class J are all sub classes of Class J?
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Feb 11, 2009
I am trying to get a handle on SyncLock and multithreading, but I am having some trouble wrapping my head around exactly how it should be implemented. I have a Public Class Utilities with a many Shared Functions. I want to make sure that each function can only be executed when there are no other concurrent calls to the same function. So If I have 2 functions, A and B in a Public Class Utilities, what is the syntax so that a function "locks" while it is being executed, preventing any subsequent calls until the "locking" thread has completed?
CODE
Public Class Utilities
Public Shared Function A (ByRef i As Integer) As Integer
[CODE].............................
I know I need to wrap the statements of execution in a SyncLock block, but I am unsure of the scope of the parameter used with SyncLock...is it private to the function, class, etc? Can the same object be used to lock both functions if they are independent?
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