Multithread Approach - How To Create Instances Of Forms
Jan 21, 2010
I have a program with 3 forms; each has a different role behind them. Form 1 loads when the program executes and the other 2 load by clicking on buttons from form 1. I would like to implement a multithreaded approach where even after clicking on form2 and form 3 I can still execute other form 1 options while form2 and form 3 contents execute. I read through some tutorials and still not to sure how to implement. I figured I need to create instances of the forms 2 and 3 but how to call the threads and control them? I did try a simple one and had some error concerning delegates.
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Nov 3, 2011
I am trying to create a new instance of a form if its not allready been created the only problem is is that the instance creation is inside a worker thread.[code]...
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Feb 2, 2011
I have a form which asks for a username and password to connect to a MySQL database. Before I load the login form I would like to place a check to see if the connection information is stored in the My.Settings.<connection string..I am using Sub New() in the Form.Designer to do this by placing the following [code]The connection form does show but when i close the form there is a blank form that shows up.
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Jun 22, 2009
Good Day. Kinda banging my head against the wall on this one. I have a Mdi application with the start form(mdiparent) and form1(mdichild). On the start form, there is a textbox and a button. Heres how I want it to work:
1. value is entered into textbox and button is clicked
2. if form1 is open with that value, Bring it to the front if not, create a new instance of form1
If Not IsNothing(frmForm) Then 'If it is something
If Not frmForm.IsDisposed Then 'it's not disposed
'loop through the open form1s and compare the form1s property to the startform textbox
'if its the same, bring the form1 to the front
[code]....
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Oct 24, 2010
how to have only one child form open at a time. I'm trying to close the open one from a second button on the parent form. or maybe there is some way to use the same button to close the first form and open the second.
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May 1, 2011
The below Code is written inside the Timer Tick event. It works fine as long as the Time and Date are not same. When the Time and Date are same it only displays 1 message. How can I show multiple message for the same date and Time ? I think this can be done If I create different instances for a form. But I don't know how many same time and Date will be there in the database. So I can't do that.
Dim frm As New frmMessage
Dim nowDate As String = String.Format("{0:M/d/yyyy}", DateTime.Now)
Dim nowTime As String = String.Format("{0:h:mm tt}", DateTime.Now)
[Code]....
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Feb 6, 2011
I am able to create internet explorer instance by using SHDocVw.InternetExplorer, how to create instances for google chrome / mozilla fire fox / opera browsers.
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Jun 14, 2010
I am using the following code to create new instances of a form
Dim nfMainForm as New frmMainForm
nfMainForm .Show()
And when I open multiple instances of the form then I need to reference controls on specific instanced of the Form then I dont know how. i.e. I need something like
nfMainForm(0).lblFullName.Text
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Jan 11, 2011
I believe one or more versions of VB.Net did away with "default instances" for Forms.
1) Was it in the 2003 or 2005 version(s)?
2) With the more recent 2008 and 2010 verions, is it possible to use a template or
change one of the files in the project so that default Form instances are not created?
I was recently looking at some of the other .Vb files in VB.Net 2008 Express Edition.
By the way, just so you know I could install a full version of Visual Studio if need be from;
2203, 2005, 2008 or 2010
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Aug 20, 2010
I'm using Visual Studio 2008 writing a Windows Forms project and I'd like to know a way to step around 'default instances' of forms. I don't like default instances, they constantly get in my way, and working in a team it's causing some really annoying confusion about the object identity of which form is actual in focus at this moment. This means I need to go threw the entire project (big) and remove ALL references to any 'default instance' of a form. But this is difficult to do as there's no errors or anything, it basically requires me to search for every text of "MyFormType." and then checking if it's accessing a default instance and fix it like that.
It'd be nice if I could just turn it off or something so I could
1) easily find all erroneous lines of code
2) avoid the accidental use of it in the future by anyone on the team
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Sep 27, 2010
I am making a visual basic game. And in the game I have a few instances where I want to call open a window (let's save to save the user's preferences) from a form, then I want to go from that form to another one.
Example:
The user has completed the new game page. I have the users choices in a host of string, integer, and boolean variables. Now I want to use a generic saving screen I made with a progress bar. When I open up the saving box, I want to close or hide the new game setup menu (whichever I need to do). Then when it is done saving I want the Saving bar to return and cause the new game form to open the actual game form and close itself.
So I guess my question is this: What is a reliable(or correct) way to poll for a return in form to signal it to go ahead with execution?
Second:
This is similar to the first question. Instead of keeping the first form open when I use the saving form; is there a way I can save the name of a page I want the saving bar to go to once it's done?
I want the user to enter their prefered username before they start a new game for the first time. So I poll the saved username setting I have and if it equals "username" I want the Username entry form I made to pop up, but once it's done I want it to immediately call the new game screen. I also want to use this username entry form on the options screen so that the user can change their accepted name at anytime; but I want this screen to return back to the options screen.
What is the accept way to do this? Is it done through stacks? (form information -> stack : load new page : Do stuff: load stack value -> goto)
Finally:
Do I have to keep a window open (not close it) to access the variables that I have defined in it, and have stored values too? Does this apply to hiding too?
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Oct 12, 2011
I have a problem that can be best solved with LINQ. I have a class that has 2 properties of which 1 is a single. I have a collection of that class and I need to select the instance with the highest single value.[code]I'm having a hard time explaining this even this is a simple task. Please ask if you don't understand.In addition to my original question, How would I create a collection containing the 5 highest Instances.
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Jun 26, 2009
In VB.net we are creating different namespace level classes. For Example, DynamicPDF - Root NameSpace Test ,Report are two sub folders in side the sub folders some classes.
[Code]...
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Dec 29, 2010
If I have a large number of classes, each similar to the other in certain aspects (they all share a common base class, but each does things differently), and I need to create Windows forms for each to allow easy changing of their values through a GUI? Create one matching form for each object in VS' forms designer, Or Use code to create the forms dynamically at runtime.
#2 makes the most sense to me, because a lot of these objects will share very common features of the form, notably "Ok" and "Cancel" buttons. But one object might need to draw a textbox on the form while another might need to draw a combobox. Not to mention, if I want to put icons on the "Ok" and "Cancel" buttons, I'd have to do this for each copy of the form in designer, and that sounds like it could get out of hand quickly.But is drawing forms through code sane? VS' forms designer is pretty sophisticated and designed to make life easier. Am I wise to consider ignoring its functionality and diving into the trench warfare of forms design through code? Or are there examples of automating form creation based on an existing object's properties?
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Sep 17, 2010
I have a TabControl object on my form with many tabs created in code (TabPages) and my problem is that the same objects that are in the initial TabPage needs to be in the other TabPages created in code, I have this done in code when the user clicks the 'New Tab' menu option, however the same code is used for any new tabs created. The problem created here is that I have an event against one of the objects that appear in the other TabPages, but because the same code is used to create any new tab pages, the event will only work on the newest tab page, if that makes sense? By the way these objects that appear on the other TabPages are properties at the top so events can be handled against them in the respective subroutine.
[Code]...
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Feb 23, 2011
I'm making a type of download manager which downloads parts of a file using HTTPREQUEST.addrange. The parts download without a problem and currently I use 5 instances of the same class to download the parts simultaneously each one downloading a different section of the file. Now my problem is that I don't want to save each part as a file then merge them later, I want to use a singular filestream and append everything asynchronously. In the code below I attempted to use the seek method but it feels like it changes the seek for all of the other parts as well.
[Code]...
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Nov 17, 2011
how do I multithread using timers. For instance 3 picture boxes that change ever 3 seconds?
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Feb 24, 2011
I have client/server app.I have a class for the tcpclient and a class for the tcplistenerIn my tcpclient class I have a system.timers.timerThe timer elapsed event fires a public event(in the tcpclient class) which the tcplistener class handles.During debugging I see the timer firing its elapsed event and calling raiseevent on the public method, yet the event is never fired in my tcplistener class.
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Sep 5, 2010
I'm working on a project. It is a windows form app which has a webbrowser. The app navigates to a url automatically, checks the url's document, and jumps to another url (depends on the document). It works fine. But, now, the problem is the project needs check many urls, so, I'm trying to make it as a MDI form project. when the start button clicked, it create a control thread, in the thread, it launchs 10 MDI forms (within main form), each form does the work for different urls. once done, then launch the next 10 urls.
It works. However, I noticed that, although 10 MDI forms are open, the navigating part in their webbrowser seems run in sequencial. I thought these 10 MDI forms will load 10 urls at the same time, do the work at the same time, but I found that it seems they do load urls one by one, not at the same time.
so, I did some research, it seems webbrowser can only be run STA mode. does it mean I can not use multithread to load different urls at the same time?
basically, I want to have a multi tab webbrowser, and navigate to different urls in these tabs at the same time.
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Mar 4, 2011
the differences between multi threading and background worker and when I should be using either.
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Mar 3, 2009
On this piece Of code I want to multithread, beginning where the for loop takes the data out of the array arydata. The threads would all do the same task.
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Aug 10, 2009
VB and programming on Windows as such. Mostly c++/gcc/linux. I am trying to build this VB app that shows a streaming video from a camera and that needs to be overlaid with some custom graphics and text. I used the code published here: [URL] to get the capture part to work. It essentially uses the avicap32.dll that most of you would probably know.
My plan:
1) Capture frames using SendMessage(windowHandle, WM_CAP_EDIT_COPY, 0, 0) and then copy from clipboard.
2) Do whatever graphics/text overlay on the obtained bitmap
3) send it to some picturebox on some form that is being shown
4) Do step 1 to 3 in a loop by a spawned worker thread.
Firstly is this a reasonable way to do what I want? or is there a much more efficient/easier way to about?
Now the specific problem: From my main thread directly if I do step 1 to 3 once UIComponent.DrawImage(VideoComponent.GetBitmap()) It shows me once captured image as it should and all is good.
Just to clarify: UIComponent is an object/instance that launches the Form and owns the picturebox I want to display on. VideoComponent is an object/instance that has started the videocapture and owns the picturebox to which the video is being captured. But if I wrap the same call above in a function and launch a thread that would start with that function as its starting point, I see a blank screen. Again, for testing purpose, I am only doing step 1 through 3 just once.
The thread part of the code is like this:
Private drawthread As Thread
public sub main()
drawthread = New Thread(AddressOf threadfunc)
[CODE]........
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Nov 25, 2009
I have this situation: a Form with a System.Timer in it (with AutoReset = False). The form has its main thread and the timer its own thread too (nothing new here). When the user press a button I need to stop the timer, wait until the timer thread has stopped its execution and do something more.
On the other side, the timer updates an item at the form so BeginInvoke is used. The code looks like this:
Button Code: Private Sub ButtonStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonStop.Click
[Code]...
The point is that I wait the main thread to let the timer thread to end its work.The problem is that this code deadlocks when the user clicks the button when the BeginInvoke is going to be called. How a simple thing like this one can be done? Looks like I cannot find a good solution to this problem
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Aug 9, 2009
SERVER
Im using this code:
Imports System.Threading
Imports System.Net.Sockets
[code]....
but when i tried to run the application, it hangs even if i wait several minutes.., is there something wrong with the code..
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Apr 30, 2011
I have a multithread program and in a thread i read a stram from ftp server and write them to a file and close it and in another thread open saved file and read it for process.but sometime when i want to open saved file i receive a error that say : cannot open file , because another user open it .i create 2 filter that surly file saved and closed , but i don't success.
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May 18, 2011
The server connects, the clients connect, one client sends a message to the server, and the server broadcasts it to the other clients. But what I want to do now is to also have the server communicate with the clients. But when I click on the server form, it freezes, and I cant do nothing.
I think this is because of me not creating a thread for the communication(I saw this on another forum), but I dont know how to do that. I copied basically all the chat program code from a site, and I dont know much of sockets and what not.
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May 18, 2011
i'm doing a chat for a project, and it works like this. The server connects, the clients connect, one client sends a message to the server, and the server broadcasts it to the other clients. But what I want to do now is to also have the server communicate with the clients. But when I click on the server form, it freezes, and I cant do nothing. I think this is because of me not creating a thread for the communication(I saw this on another forum), but I dont know how to do that. I copied basically all the chat program code from a site, and I dont know much of sockets and what not.
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Nov 15, 2011
How can I use a text box on a multithreaded client so that it will appear in the command line of the multithreaded server?We were given this code to work around/tear apart:
Imports System.Net.Sockets
Imports System.Text
Module Module1
[code]....
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Jun 27, 2011
i am new with multithreading in vbnet. i got this error.Cross-thread operation not valid: Control 'lvSample' accessed from a thread other than thethread it was created on.this is my code.
Private Sub xFormLoad(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim t As Threading.Thread
[code].....
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Jan 21, 2010
I have a thread executing the following:
vb
Do UpdateVis()
System.Threading.Thread.Sleep(Interval)
Loop
UpdateVis is as follows:
[Code]...
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