Asp.net - WebRequest Async CallBack Code Only Gets Call The First Time?
May 28, 2012
I am an absolute beginner on ASP.net (VB.) Please pardon me if the question is too obvious for the experienced members.I tried to make a simple WebRequest in the async mode in case the target URL takes long to provide the data. In my code below, I just want to see if the callback block (RespCallback) is called correctly every time. If all goes well, lblResult should have the string '123' appended to it every time I click the button which calls the 'GetData' sub.
However, the lblResult only shows 123 after the first click. After the subsequent click, the lblResult only gets appended with '12', as if RespCallback is never called. When I tried to debug this in Visual Studio, the execution actually stepped right into the RespCallback part and the lblResult.Text watch actually shows '123123' but the resulting Web page always shows only '12312'
I am sure I am missing something basic here, but I just don't know what. I was even guessing that it has to do with browser cache (hence the result changes for the second time) but I don't know how to fix that either.
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.
I think this is a simple question for you, but I don't understand other cases of webRequests, so I asked here: How can I make this webRequest asynchronous? Dim sBuffer As String Dim oRequest As WebRequest = WebRequest.Create(url) oRequest.Method = "GET" Dim oResponse As WebResponse = oRequest.GetResponse() Dim oStream As New StreamReader(oResponse.GetResponseStream()) [Code] .....
I have a console app that is supposed to async call a web service...i don't get any errors but the completed handler doesn't seem to complete correctly. I have a subroutine with a loop that is supposed to fire off say 6 seperate calls to another routine that calls the service. The completed event handler routine puts data into the database..If i put a thread.sleep under the call to the routine calling the web service. The completed event handler fires but only one record is put in the database instead of the hundreds expected and only that one webservice call appears to fire.I should mention that this works as expected when calling the sync method of the web service within a console app and the asyc calls work as expected from a windows forms app. I just need it to work async within a console app..
I am still learning about Get / Post statements in VB, and wondering if you have to call the Get commands to images, and what not, or just the main Post / Get statement and the rest will auto-load?
I am trying to convert a DLL function call which has the Callback function routine called within the DLL function call.The DLL function call signature is like this:
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()
I have the below code. What happens if the Upload method takes more than one minute for completion? Does the timer kick off another call to the Upload method immediately after one minute is over or Does it wait until the method finishes executing? I am implementing this as a windows service.
Protected Overrides Sub OnStart(ByVal args() As String) Dim tmr As Timer = New Timer(New TimerCallback(AddressOf Upload), Nothing, 1000, 60000) While Not tmr Is Nothing
I am trying to use the code from Microsoft for an Async Socket connection. It appears the listener runs in the main thread locking the GUI. I am new at both socket connections and multi-threading all at the same time. Having a hard time getting my mind wrapped around this all at once.
I have a Windows program (sort of a crawler) that queries an internet website to collect data from. I use WebRequest and Webresponse. The first time I run the program everything works fine. However the second time I get a Time out exception on the WebRequest.GetRequestStream method.
I'm trying to write a 'developer friendly' wrapper for the Windows API EnumWindows - the problem is that the API uses a callback function that gets invoked on another thread, where as I want my wrapper function to simplify this and make it more useful by working like any other normal synchronous function and just returning a value.
Now if the API just called the callback once that would be fine, as I would just call the API and make the wrapper function wait until it got a signal from the callback function telling it to continue... but the API calls the callback function over 100 times (once for every window handle that exists). The biggest problem is that there is nothing that indicates that any particular call to this callback function is the last one, so my wrapper function has no idea when it is safe to continue and return the list of window handles to the caller.
The only solution I could think of is to do this:
1. The wrapper function calls the API and starts a timer that waits 2 seconds before it raises the Elapsed event. The wrapper function then pauses until it receives a signal (ManualResetEvent)
2. Each time the callback function is raised by the API on a different thread, it stops the timer (so this is before the 2 seconds have elapsed), adds the current window handle that was passed in by the API to the list of handles, then starts the timer again.
3. If the timer reaches its 2 second interval then it is assumed that we are at the end of the windows because otherwise the callback would have stopped the timer. So the timer's Elapsed event handler is what signals the original thread (that the wrapper function is executing on) to continue as we now have a complete list of windows to return.
This works fine and does exactly what I want... but I dont like it.
I dont like forcing the caller to wait an extra 2 seconds after the API has done its last callback but more importantly I dont like assuming that the API will never take longer than 2 seconds between callbacks. In reality on my PC it is never anywhere near that long between callbacks, it is something like 200 miliseconds, but I have no idea how long it would be on a slower PC and I want this to be completely reliable.
i am using System.Net.WebRequest.Create(url) to download html code, but it missed some data. if i use IE to view page and click "view source", all data will be showed.
my code:
Dim req As System.Net.WebRequest Dim resp As System.Net.WebResponse req = System.Net.WebRequest.Create(url) resp = req.GetResponse()
I connected to the Informix server using RazorSQL, created a stored procedure and tested it, getting the expected answer, so the procedure exists in the database in some form.
I then run the following code:
If ConnectToInformix() Then Dim cmd As New IfxCommand("dc_routeHasOutstandingQuantity", conn) cmd.CommandType = CommandType.StoredProcedure
[Code]....
This error does not occur when calling the stored procedure from a live SQL connection.
I am working on a windows application project on NIST time synchronization, but can't get a proper solution for it. If anyone can send me the code to synchronize time from the global time server in VB.net or C # code
Im trying to create a software which can post into yahoogroups.I've done trying to log in yahoomail but my problem is when I am going to post in yahoogroups, I am turning back in to yahoo log in page.
Is there a way in VB.Net to determine if the timezone the current system has daylight savings time in effect? Of course I can get the offset from GMT using the "z"/"zz" formatting option, but that doesn't tell me if DST is in effect for the current timezone or if the current timezone is in standard time...or if DST/Standard time aren't even an issue in the timezone for the system.
I have a piece of JQuery AJAX that calls a VB.NET code-behind (class) that returns string data. It grabs some latest stats on a particular server. Now the code works, but the first time I press the refresh button data is returned and the alert "Refreshed" is shown on screen.
But if I press it again, the alert box "Refreshed" is shown twice, I click again three times! and on and on, until the time-out kicks in.It seems to be coming from the AJAX call and no where else. I'm at a loss at what could be calling this, I've tried deleting the data returned after success but no joy.
Actually we have a system for doctors in dispensary and when they try to access records for the patients from doctors module they able to do it but when they try to modify records and save it gives an error "Run-time error '5': Invalid Procedure call or argument" We are using oracle 8i as database and vb6 as fronend.
1) The first function (call it GetValues()) returns values in a SQL database as a list via a stored proc. One of the fields is DateTimeSubmitted. All of this data is displayed on my webpage using a repeater control. It works fine.
2) The second function (call it NiceDate()) I created to change the DateTimeSubmitted to a nice date such as "one minute ago" or "yesterday".
My problem is I have no idea which is the best part of the process to do the conversion (at point of data extraction or in pageload etc.) or in fact how to do the conversion.
How can I call a javascript function from code behind?The most popular response is "ScriptManager.RegisterStartupScript" however, that does not work in my situation. I have a vb class that is doing a database check to see if a record exists. If exists, then call a javascript function to display an alert("Record exists") So I am doing something like
Dim strMessage as string = "javascript:RecordExists('Param');"
I open an Excel workbook from VB.Net and then want an event in the workbook (such as pressing a button) to activate code in VB.Net. How do I accomplish this type of callback?
I have a function that is responsible for populating an SSRS report. The user presses a button and I go out and check to see if there is data. If no data, I provide a NO DATA message. If there is data I call the SSRS report which I would like to open in a new window.
<script type="text/javascript"> function openWindow(url) { document.forms[0].target = "_blank"; } </script>
I have ShowValue working. Now, on the last line I need to call the function newFunction to repopulate the dropdownlist object on the onClick event.
I am getting errors when I click the dropdownlist down arrow.
How do I get the two to hand shake with each other?
My code:
Public Sub ShowValue(ByVal sender As Object, ByVal e As System.EventArgs) lblupdatePanel.Text = DropDownList1.SelectedValue.ToString Dim LocationDescription2 As DropDownList =
I'm working in VB.Net and I'm trying to make a piece of code more generic.In fact, there's a big Select Case statement that build a ProxyServer based on a value passed in parameter (a string).
Select Case _strNteraHL7 Case Constantes.NomPRPMIN306010 strUrl = ObtenirUrl("ProviderDetailsQuery", _strVersion, _strEnvir, True, _blnSimulCAIS, _blnSimulPDS, _blnSimulPDSSIIR, _blnSimulPDSInteg)
[code]....
or something similar, so I can remove all those big switch cases, that repeat the same thing 30 times.objWsHL7 being an object or type "object" at compiling.Again, in another switch case statement,
objMsgHL7Out = _objWsHL7.ProviderDetailsQuery(_objMsgIn) objMsgHL7Out is a System.ServiceModel.Channels.Message _objMsgIn is a System.ServiceModel.Channels.Message _objWsHL7 is an Object
