Invoke From Another Class?
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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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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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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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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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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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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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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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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Aug 27, 2010
I have a filesystewatcher object. On it`s event it runs a procedure which fills a treeview with a data. I had problems with treeview methods, but when I run them using invoke method everything is ok. But I still have one problem. When I load the form for the first time, everything works fine. But, when I then close the form (me.dispose, me.close), and load it once again, when Filesystemwathcer start the procedure i have an exception "invoke or begininvoke cannot be called on a control until the window handle has been created" trying to run a treeview.invoke method?
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Apr 10, 2009
What is Platform Invoke Service (P/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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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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Oct 12, 2009
how do i create dll application in vb.net? how do i call a dll application from an exe application?
using VB.NET, is there sample code where an exe application invokes a dll appliction?
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Mar 5, 2009
Is it possible to execute some sort of code to determine whether or not it's a good idea to call Invoke? I dunno what you would do once you'd found out you can't but it could be useful for detecting some dead locks (like the one I have a the moment).
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Apr 15, 2010
I have put this code in the global form Inherits System.Windows.Forms.Form. And then in the form that will inherit this from the global Inherits MenuStrip. "MenuStrip" is what the global form is called. But keep getting this error: Error1Base class 'MenuStrip' specified for class 'Lesson2' cannot be different from the base class 'System.Windows.Forms.Form' of one of its other partial types.
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Nov 11, 2009
Public Class StateObject
Public workSocket As Socket = Nothing
Public Const BufferSize As Integer = 1024
Public buffer(BufferSize) As Byte
[CODE]....
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Jan 23, 2012
I have the HTML Help Workshop, and I can create a .chm file. When I add the file's name as a help file in the Project Properties form, pressing F1 invokes I also have a help menu item (which has F1 as a shortcut key), but clicking on the item produces no response. When I created the help menu item, VB generated stub SUBs for mnuHelp_Click() and cmdHelp_Click(); what code do I add to the SUBs to bring up the help file?
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Apr 19, 2009
Alright, all I want to do is submit a form on this website.The program is simple enough - automatically logs me into the site.For reference; the website is ( url.. )I know, the game is lame..
Anyway, I have already figured out how to fill in User/Pass fields.But I am having problems understanding how to access the Login button.It should be simple, but the button itself is not assigned a name at all.Here is the only information given on the button itself [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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Jun 25, 2010
Is there a one-stop shop for determining which .Net types/attributes to use, given a native type?
[Code]...
Also, as a related aside, what's the most reliable place for looking up marshalling declarations for Win32 functions?
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Apr 1, 2011
Private Delegate Sub SetControlValueCallBack(ByVal value As Integer)
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Apr 22, 2011
I wish to check the hard drive space used in a folder on a hard drive. This will happen continuously as a service, so it will be calculating the space used for thousands of folders all the time. I know that this code can be done easily in dotnet, but it seems to take a really long time. Are there any APIs to do this more efficiently, or does the entire looping process have to occur to do this check?
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Nov 16, 2011
How would one invoke a readonly property?
ListView1.SelectedIndices.Count
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Jan 30, 2012
I use this code to invoke a function from a string, which I build in my application:
Public Class Form1
Dim f As New Foo
Dim methodName As String
Dim result As Object
[code]....
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Aug 20, 2009
1. On the main form a scanner class is instantiated that (in the scanner's constructor) sets the scanner settings (baud rate, parity, etc) and opens the scanner for use
2. A barcode is scanned (via a scanner connected to the device in a seral port) while on the main form
3. In the scanner class, the DataRecieved event gets the needed info from the scanned code.
4. Then that info is passed back to the main form to a method RunCommandCode (which takes the scanned info as an argument)
5. On the main form the RunCommandCode calls another method CommandCodeHandler, passing the scanned info again
6. In the CommandCodeHandler sub a method is called in a Utils class (SetSelectedTab), which interacts with the form itself (determines how many tabs exist on a tab control), which is the reason for the invoke in the first place
So, before I figured out I needed to use the Invoke method (and, more specifically, that the scanner was working in a different thread), I was getting an error in step 6 on the line that got the TabControl.TabPages.Count.
[code]...
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Jan 31, 2011
I dont know how to invoke a cmd prompt from vb.net window. from the vb.net i have tp ping an ip adress of a system in the cmd prompt.
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May 25, 2009
I've got a messagebox that pops up after so long and gives you a yes no choice, if the user clicks yes, I need it to invoke, or press the button named GetA. How do I do this?I tried Invoke(GetA) but that did not work!
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Apr 13, 2011
I was wondering if this is known / expected behavior. By design?Is it documented somewhere?
My 'real' code does need something to keep one thread from accessing a listview while another is busy clearing and refreshing the Items collection, so it's not as easy as omitting the synclock section in the example below (The SyncLock in my case is on the ListView).
This code, which can be pasted over a new empty form's user code class, deadlocks during the Invoke call. It doesn't reach the entry point of SetText (setting a brakpoint there, the deadlock occurs before the breakpoint is hit).[cod]e...
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Feb 14, 2011
I am using VS2010 (VB) and I am trying to dynamically call a function in another assembly. From my research, I seem to be doing it correctly --- but appearenty not since I get a run time error. {apologies if the code does not come out formated -- the code block helper is not loading for me}Here is the proto type of the function I am calling.
Public Class PrintLabel
Public Function ProcessMany(ByVal listRequests As List(Of Request)) As Windows.Forms.DialogResult
End Function
[code]....
When I step through in debug mode all seems great until I hit the .Invoke() line. It is then I get a paremeter count error exception.
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Mar 5, 2009
I'm trying to figure out if it is possible to instantiate and invoke a delegate by name, rather than explicitly. I think the code below explains it fairly well. I want to accept a function name and then instantiate the delegate based on that. In the example I use a select case, but I want to eliminate that and just use the methodName argument itself.
Private Delegate Sub myDelegate()
Private Sub myDelegate_Implementation1()
'Some code
End Sub
Private Sub myDelegate_Implementation2()
[Code] .....
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