Handle Multithread Situation And Don't Lock?
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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May 20, 2011
in VB is there any situation whereby x = Nothing is not the same as x is Nothing?Also, x <> Nothing vs x IsNot Nothing.
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Jan 4, 2011
i have this code that i am using to read from an excel spreadsheet but it i giving me an error saying that i am not not giving the exact name of the table.i have uploaded the excel spreadsheet as well. [code]
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Aug 18, 2011
The following is a function to read a value from a field in a database, then add a value to it, and restore it.The three possible columns it reads from are Hoodoo, Give Them, Snug.It works no probs for hoodoo and snug, but not for Give them..[code]Index Out of Range Exception was unhandled. The text visualizer says that the value of night is give them.I can see the column give them in the database, so what could be going on?
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Sep 14, 2010
So, I have an app that uses a SQL Server express db. I have about 80ish tables all with a primary key but no foreign keys. (The reason we have no foreign keys is because of how we do our sql client-to-server replication. It's not true replication but it's a sync system that was in place when we took over the app. We have no guarantee what records are going to make it to the database first when a client syncs to the server so it is possible that a record would make it to the database with a foreign key that points to a nonexistant record). We use a type-per-model convention. For each of our business objects there is a table in the db. We currently use stored procedures for every database transaction. This means for every new class there is at least 4 new stored procedures (crud). We have abstracted out our data access layer from our business objects. Each business object has a corresponding businessObjectDAO.
My question is, is entity framework feasible for me to move to? With no foreign key relationships I'm going to have to set up every association between tables manually.My biggest hang up right now is trying to figure out how I map my DAOs to the EF partial classes. Should I be creating one big .edmx or multiple? A lot of questions I know. This is my first big architectural type decision and I've been given the go ahead to make the change if I think it is beneficial and feasible. Maybe I should try Linq-to-SQL? NHibernate is out because we're not allowed using open source products in production (stupid, I know).
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Jun 11, 2012
So I have[code]...
It would give me 5 instead 4 results, since <title>My Channel</title> is considered one of the item under channel. I'm just wondering if there is anyway to loop through only the 4 item elements.
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Jan 26, 2012
I have a Check Box that the use checks to indicate that a specific situation is present. When the User checks the box he gets a Message Box reminding him that the condition must be fulfilled. This works fine and the database reflectthe fact that the Check Box is filled.
At a later date, if the user calls this record and fills the form, the Check Box is triggered and the message Box appears in the middle of the form fill operation.
Is there a way to prevent this from happening. I want the Check Box checked but don't want the message box if the change is triggered by the fill process.
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Dec 17, 2009
I want to create multiple dataset depend on situation. dataset number may vary each time.how can we create multiple dataset
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Sep 8, 2011
.Cast(Of Double) extension method not working in a particular situation.However I can get my own extension method .CastToDouble working.Would you call this a Framework bug?see the commented out line of code in the code below.Similar code posted in my last post in this thread: http:[url].....
Option Strict On
Option Explicit On
Option Infer Off[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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May 20, 2011
in what situation will an item in System.Collections.Generic.List not be removed successfully?url...The way they phrase it makes me think that it is possible that a Remove operation on an item found in the List(Of T) could actually fail.
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Jun 11, 2011
Anyone know why the Mouse_Leave event fires when you don't leave the control with the mouse pointer?Put a large button on a Form so your mouse pointer does not leave it easily.Then try this codeWhen you do, leave the mouse pointer in the middle of the button and then click the button.By the way, if you uncomment the 1st line of code in the Button Click event and comment out the MessageBox, this does not happen.Can someone please explain this behaviour?
Option Strict On
Option Explicit On
Option Infer Off
[code].....
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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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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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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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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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May 27, 2009
I am trying to successfully multithread a piece of software I have been working on. I have an array of threads 'gen' already working, calling to a method taking a single integer as a parameter (done via typecasting).Now in this thread, when the function gets processed (for each thread a roughly 500 iteration while loop) the index seems to be getting mixed up. As far as I can tell, my threads are messing with eachother and warping values. Now this is happening in locally declared variables inside this function, not global variables.It may be useful to know that I am using a WebRequest via a call to another method. Don't know if that makes a difference or not.
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Jul 7, 2009
I'm trying to manipulate something that is in a different thread, and I know I need to do something by the way of Invoked procedure, but I'm unclear on how. I looked up some examples here on the forums and tried to follow the basic template, but I continue to have the same problem. how to use invoke correctly.
Private Sub getMessage()
For Me.infiniteCounter = 1 To 2
'Try
[CODE]...........................
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Aug 16, 2009
I currently have a browser go through the same list of sites one by one and gather updates. The problem though this takes awhile. Can a browser be multithreaded, (so it could visit several sites at a time) and if so would this take up a lot of server resources?
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Aug 31, 2009
I am doing this within a thread:For Each item As ListViewItem In lvUsers.Items and I am getting: Cross-thread operation not valid: Control 'lvUsers' accessed from a thread other than the thread it was created on.I have been able to adjust a control in a way using something like:
Public Delegate Sub ListAddNameInvoker(ByVal text As String)
Public Sub ListAddName(ByVal text As String)
If lvUsers.InvokeRequired Then
[code]....
But how do I get data from a control and pass it to another thread?
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