Asynchronous Programming Using CallBack?
Feb 1, 2010
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
[code]....
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Feb 1, 2010
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.
My thoughts are:
Private Function BeginConnect(ByVal URl As String, ByVal callback As AsyncCallback, ByVal state As Object) As IAsyncResult
'Some Code
[Code].....
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Aug 17, 2009
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
[code].....
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Feb 12, 2011
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)
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Feb 23, 2010
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
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Feb 2, 2011
I am facing problem in asynchronous socket communication.
1)I wanted to perform connect(from client to server) operation on enter button and send the data whatever client want to send and disconnect from server. And again client should get connect to server whenever client wanted to send data. this is the mechanism.
i.e how to reuse the socket.
2)Again Server should able to send the data to client.
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Jan 28, 2012
I have recently taken a liking to programming, and have programmed a few games in C#,my friend has asked me to program an application for him to use in his shop. But I have no idea of what language is best suitable?
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Feb 18, 2011
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#.
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Jun 19, 2012
I'm trying to use a .DLL which Callbacks a Function of my project, but I can't get it to work.
Declaration from .h file of .DLL
void DLL_EXPORT SetEntity_CallBack(bool Active, _
void (*Entity_Callback)(int Site, int Application, int ID, _
[Code].....
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Mar 15, 2009
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
[code]...
How can I implement asynchronous calls so that the my application can behave without locking up?
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Oct 12, 2010
I 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?
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Feb 12, 2010
I 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?
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Feb 2, 2012
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?
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Mar 3, 2011
I have a C++ dll that contains a callback. The callback has one parameter that is passed in and one parameter that is passed out. The parameter that is passed from C++ is a variant. So, we are going from a variant in C++ to an object in VB.NET. The function works. However, It seems that there is a memory leak on the VB.Net side. This must be a Marshaling issue. I have tried to use the MarshalAs Functions, but to no avail.
VB.NET
Declare
Function EnableWriteNotification
Lib
[code]....
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Jan 4, 2011
there is error when i use callback function A callback was made on a garbage collected delegate of type 'skynet1!skynet1.Form1+myCallBack::Invoke'. This may cause application crashes, corruption and data loss. When passing delegates to unmanaged code, they must be kept alive by the managed application until it is guaranteed that they will never be called.
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Aug 8, 2011
I am working on a Twitter application and with the authentication process, Twitter returns Two Tokens with a Callback URL, For example: [URL]. How do I extract each token and put them into separate strings?
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May 12, 2011
I am writing classes in VB.Net (both managed). The main class "A" creates an instance of "B". Class "B" must call a method of Class "A". I need to know two things (syntax, etc...):
1. How does class "A" tell class "B" what method to call?
2. How does class "B" call the method?
The method must pass back an array of Shorts (in this particular example), either as a return value, or as a ByRef argument.I don't want to use an event if I don't have to. The execution is timing critical. (I assume event handling involves a lot of overhead by the operating system, but I may be wrong.)
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Oct 15, 2011
I 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.
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Jan 9, 2010
I 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?
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Jan 24, 2011
I'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.
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Jun 3, 2011
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
[CODE]...
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.
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Jun 9, 2011
Download file asynchronous using sockets
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Jul 12, 2011
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.
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Jun 16, 2010
I 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.
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Jan 17, 2012
I 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?
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Feb 6, 2011
I 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..
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Feb 2, 2011
I do not know Why I am recieving a TimeOutException in my code:
Dim Uri2 As New Uri("http://localhost:8733/Design_Time_Addresses/ssWcfService/Service1/")
Dim binding2 As New WSDualHttpBinding()
Dim callback = New MyCallBackClient()
[Code].....
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Feb 21, 2012
I am a relative newcomer to Windows programming and VB.net. What we are trying to do is call a function in an existing, 3rd party COM dll. This function requires a callback parameter, whose type is an interface also defined in the dll.In our VB.net application, we have added the dll as a COM reference, and created a class that implements the interface in the DLL. We then send an object of that type as the callback parameter. This compiles fine. However, when we run the application, we receive an error stating that the program is unable to cast the object from our existing type to the interface type.
I suspect that there is a simple fix, but so far, my efforts to find a solution have come up short. If anyone could point me in the right direction,
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Jun 12, 2009
I have a bunch of operations that need to be executed simultaneously. For this I'm using the thread pool to execute the tasks. I'd like to know if it's possible to consume some sort of Async Callback (similar to BackgroundWorker.DoWorkComplete) when each thread is finished. The reasoning behind this is that I have a windows service running that uses IPC to update a GUI and I need to know the time at which each specific thread finishes I've used background workers to do a set of tasks and they work perfectly, however, they take longer than I would like. I've timed the execution on my BGW method for a designated number of said tasks and it took 27 seconds, and the same set of tasks takes 4 seconds using the threadpool method. I've also tried using managed threads, to the same effect as the background workers.
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Mar 23, 2011
Situation: i've created several forms with a datagrid:formwithdatagrid1formwithdatagrid2formwithdatagrid3.... These datagrid can be filled manually or with a selection list. I've written this selection list a a new form (frmSelectionList), witch is called with a SQL instruction, now this selectionlist calls a funtion in formwithdatagrid1 to return the selected value. Question:How can the same selectionform being used for all datagridforms?
[Code]...
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