I have a small VB.NET application built using VS 2008 and .NET 3.5.Very simply, there is a timer that kicks off every few seconds to download an XML stream from the web. I look at this stream and manipulate it.The problem I am facing is that the remote web server may not respond in a timely fashion to the following line of
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How can I implement asynchronous calls so that the my application can behave without locking up?
I am currently writing a program in Visual Basic 2008 express edition to read and write to tags on an Omron PLC. I am using the DeviceXPlorer OPC Server V4.1.1.1 program to connect to the Omron PLC. I have made two programs, one is a form program which works fine, two is a windows service program where it does not let me connect to the OPC Server. The connection code is identical, the only difference is the windows service code is called by a timer. The timer works fines and jumps into the connection code, but stops at the line
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my project was intially mandated to be done in c#.however a large contributor to the project wrote much of the business logic, which he knows well, in vb.net.How difficult would it be to convert the following c# code into vb.net.
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how to apply the code in the module?
this is my code:
sqlstr = "update StudentGraduateTable set LastName ='" & txtlastname.Text & "'," _
& "FirstName ='" & txtfirstname.Text & "'," _
& "MiddleName ='" & txtmiddlename.Text & "'," _
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I'm trying to apply a code to a group of labels (actually all the labels but one in particular).I used to use:
For Each lbl In My.Forms.Form1.Controls
If lbl.name.ToString.Substring(0, 1) = "x" Then
'Code
End If
Next
I'm playing with a simple string replacement editor for editing VB.Net functions outside of VB. Is there a way to apply VB.Net code formatting to a string?
For example. The txtboxCodeEntry looks like this:
If strVar="dummy" then 1 else 0 Endif
I would like it to "autoformat" to:
If strVar = "dummy" Then
1
Else
0
End If
The formatting would match whatever formatting VB.Net does when you're editing code in the Visual Studio IDE.
I was using VB 2008 to code using applications. An example of something I coded was hangman. I was wondering if its possible to somehow use the application code and apply it to a form.So for example with the code below how would one go about putting into a form? If this isn't possible, what are the main difference between form/application coding? How would I go about coding hangman for example on a form, what are the main difference between the two??
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Between testing sessions on my windows service, I'm changing code (little tweaks here and there). For more detailed debugging, I've had the application send messages to a text file everytime it does something (executes a new procedure, catches an exception, etc).
I've been doing this for a while, but ever since yesterday, it appeared that the new code wasn't being used. To test this, I changed the name and location of the log file that the service would use, and re-installed it shortly after a new successful build. As it turns out, the service is writing only 1 message (about a timer being started - which is only supposed to happen after it's logged the start of the service) to the old text file. It looks to me like my service isn't using the new code in my Service1.vb file, Like the old code has been cached or something, and the service is installing from that.
how to apply inserting data syntax into the Try catch..
sqlstr = "insert into StudentDiplomaTable (LastName, FirstName, MiddleName, StudentNo, SoNo, CourseTaken, Honors, DateofGraduation, Copy, DateIssued, DateRealesed, Notes) values ('" _
& txtlastname.Text & "','" _[code]......
I am programming in VB 2010 and have a question. I have some code that currently only applies to one text box. As you will see, I have sub setup to handle multiple textbox events. My question being, Is there a way to take this code and apply it to all textboxes that are being handled?
VBCode:
Private Sub TextBoxes_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles fnameTxBx.TextChanged, _
lnameTxBx.TextChanged, streetTxBx.TextChanged, cityTxBx.TextChanged
Dim theText As String = fnameTxBx.Text
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I have this code obtaining data from a sensor that is sending a string that contains 4 numbers separated by a tab and terminated by an end of line/ I am trying to use an asynchronous callback to get the data over TCP. That problem is that the callback function is not grabbing the complete string. Sometimes it will, other times it gets half in one retrieve and half in another. I need the callback to hold off until it gets a newline character.
Code:
Public Sub readVaisala()
Dim ip As String = "192.168.1.30"
Dim portNumber As Integer = 23
Dim time As Int32 = Now.Second * 1000 + Now.Millisecond
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How can I set up an asynchronous web service in asp.net?
I want to call a webservice to post some data to a database, but I don't care if the response failed or succeeded.
I can use .net 2.0 or 3.5 only and it can be in vb or c#.
I have a class with a mthod which does a a time consuming task. I know how to start the method in a separate thread using the Threading.Thread class. What I want to do is use callback so as to have the method report its result to another method when completed. I chose to use the asynchronous Begin/End call pattern.
Private Function BeginConnect(ByVal URl As String, ByVal callback As AsyncCallback, ByVal state As Object) As IAsyncResult
'Some Code
End Function
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i'm creating an Asynchronous socket programming in vb.net. i've utilised the code from Asynchronous client and server code frtom the following links:m a new user so could post only one link fully)When I try to connect the for more than one client the second client always waits until the first clientcompletes the call. i want the clients to accept calls at the same time
View 1 RepliesI am writing web services with VB.NET (2.0). The client side will use different technologies such as Java and Siebel. So, if I write asynchronous web services, is it possible for different platforms to consume them? I know it is quite easy with a consumer having .NET platform, but not sure for different platforms. Is it enough for them to have asynchronous ability, or should it be a similar platform?
View 3 RepliesI noticed that HttpWebRequest freezes the UI while it's waiting for a web page to be downloaded:
[code]
If someone's done this before, what is a good way to keep the application responsive?
I am using a BackgroundWorker, an OleDBDataReader, a DataGridView to retrieve records asynchronously from an Access database. I call ProgressChanged event from the DoWork event every time I retrieve a record. In ProgressChanged event I add that record to the DataGridView and also update a label. There are about 2000 records to retrieve.I have two problems:Although I'm running an asynchronous operation, the UI remains unresponsive unless I use Thread.Sleep() inside the DoWork event (Why?). Using Sleep() method with an argument of 1 causes the process to run 20 times slower! (Process takes about 1 second if I comment out the 'Threading.Thread.Sleep(1)' line, compared to 20 seconds if I use it.) What can I do to get a responsive UI and a fast background operation (at least not 20 times slower!)?The other problem I am facing is: if I close the form while the asynchronous operation is ongoing, I get this exception (I think in the ProgressChanged event): Exception has been thrown by the target of an invocation. I tried using FormClosing event to end the process but no luck. How to fix this?
View 5 RepliesI made a TCP server which communicates with multiple clients at once, but I can't seem to be able to make them stable. When one of the client sends 100 packets to the server, the server receives only a few of them.Here's the client code in PasteBin. It shows how the client connects to the server and then sends 100 messages in a For loop to the server.And here's how the server handles the connection. I couldn't paste the full source as it's hundreds of lines long so let me know if it's missing any mandatory parts and I'll upload them as well.
View 1 RepliesI create an automatic ftp file downloader by using FTPwebrequest. In which, is there any possible to download multiple files simultaneously using Asynchrounous and threading concept?
View 1 RepliesI'm using asynchronous to send/receive from a website I want to block the BeginGetRequestStream method which I have done, using
Code:
WaitEvent.WaitOne(1000 * 20, false);
the problem is that it blocks the UI, which I thought it did not so it basically works like GetRequestStream which does block the UI.
I basically have a few thousand transactions 7,000 - 10,000 transactions to process over a short time. The flow goes like this.
---> ----> ---> ---> receive (1000) as each transaction takes approx 2 seconds so if i were to process synchronously it would take all night......
Now first i would like to ask if i am going about this the right way ? the service i am communicating with is not .net but is built to handle large amounts of requests. I have obtained the following code that suggests it will do what i am after
dim strxmlreq as string = '(this is where i input my xml string)
Dim request As HttpWebRequest
' Create the request
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The problem i have is if the above will work for me where exactly do i catch the returned xml string ? I assumed "result" would be the xml output string.
Download file asynchronous using sockets
View 8 RepliesI have a class with a mthod which does a a time consuming task. I know how to start the method in a separate thread using the Threading.Thread class. What I want to do is use callback so as to have the method report its result to another method when completed. I chose to use the asynchronous Begin/End call pattern.
My thoughts are:
Private Function BeginConnect(ByVal URl As String, ByVal callback As AsyncCallback, ByVal state As Object) As IAsyncResult
'Some Code
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I have been trying to figure this our for far too long and I cannot get my head around it. Every example I have seen seems to be far more complex that I need. I have a web service in my project (.asmx). I want to call it very simply from a button on a webpage.
Click
Run service asynchronously
return control back to webpage (web
service running in background)
The scenario is that an ASP.NET webforms page will call a web service in an async manner to make about 8 web service calls to various providers for data. I would like to run them in parallel to speed things up. I also need to wait for them all to come back before moving on.
View 1 RepliesI need to make an asynchronous call to a method which for the sake of simplicity counts from 1 to 100. If an exception is thrown during the methods counting process, lets say at 50 I need to stop the methods execution, dispose of a few objects and restart it at 51 but have no idea how to go about it.I basically need to raise an event from the method to the main thread and restart the asynchrounous method.
View 3 RepliesI am developing a form application in VB .Net with a main thread and two other threads that reading values from two serial ports, do some work and raising events to return values when each thread ends.The handlers for the events are in my main thread.Is there any possibility the two threads to raise events the same time or some other event (button click event for example) raised the same time with a thread finished event? What happened then? Is there a way to make asynchronous event raising?
View 11 RepliesI have closed the client socket using client.close() but netstat command shows the same socket in time-wait state.Because of this I am unable to reuse the socket..
View 2 RepliesVB.NET 2010, .NET 4/I have a System.Timers.Timer object that does some work on its elapsed event:
Private Sub MasterTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles MasterTimer.Elapsed
MasterTimer.Enabled = False
'...work...
MasterTimer.Enabled = True
End Sub
My problem is that the work that it's doing sometimes gets stuck. Part of the work is serial communication so it might be getting stuck waiting for a response from something. I've already modified my serial communication code a bit to hopefully solve the problem. However, this timer is basically the heartbeat of a production control application and it is very bad if it were to stop for any reason. I was thinking that it might be nice to put in a fail-safe timeout so that, if the "work" is taking too long, the timer could re-enable itself and try again. I was thinking of something like this:Move the work into a subroutine and create a delegate:
Private Delegate Sub WorkDelegate()
Private Sub Work()
'...work...
End Sub
Call the work by invoking the delegate and then use WaitOne(timeout) on the IAsyncResult to specify a timeout:
Private Sub MasterTimer_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles MasterTimer.Elapsed
MasterTimer.Enabled = False
Dim workDel as New WorkDelegate(AddressOf Work)
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In that it would re-enter a subroutine that is already running? Is there a way to abort Work() if it hasn't finished after the timeout? In other words, just cease execution of Work() if result.IsCompleted Is False after WaitOne?
I am attempted to write a small asynchronous socket library that I can use to create a client/server application. I can get all of the code to run fine if I leave it in the form, however if I try to move it out into its own class, I cannot figure out how to update the form with connection status, things like that. Below is code, shortened a bit just to make this easier to read and type.
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There is actually more to that class, but I never get anything after the first message goes out. I'm not sure where to go from here. I've tried lots of different methods that I've found on the google searches, some from here, some not.
