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  • What determines which Javascript functions are blocking vs non-blocking?

    - by Sean
    I have been doing web-based Javascript (vanilla JS, jQuery, Backbone, etc.) for a few years now, and recently I've been doing some work with Node.js. It took me a while to get the hang of "non-blocking" programming, but I've now gotten used to using callbacks for IO operations and whatnot. I understand that Javascript is single-threaded by nature. I understand the concept of the Node "event queue". What I DON'T understand is what determines whether an individual javascript operation is "blocking" vs. "non-blocking". How do I know which operations I can depend on to produce an output synchronously for me to use in later code, and which ones I'll need to pass callbacks to so I can process the output after the initial operation has completed? Is there a list of Javascript functions somewhere that are asynchronous/non-blocking, and a list of ones that are synchronous/blocking? What is preventing my Javascript app from being one giant race condition? I know that operations that take a long time, like IO operations in Node and AJAX operations on the web, require them to be asynchronous and therefore use callbacks - but who is determining what qualifies as "a long time"? Is there some sort of trigger within these operations that removes them from the normal "event queue"? If not, what makes them different from simple operations like assigning values to variables or looping through arrays, which it seems we can depend on to finish in a synchronous manner? Perhaps I'm not even thinking of this correctly - hoping someone can set me straight. Thanks!

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  • jQuery: How to fire event when all asynchronous calls return?

    - by Jeremy
    I have a jQuery application that loads data from five asynchronous server calls. I do not want to display any data until all five calls return. (I plan on displaying a Loading message until that happens.) How can I detect when all five calls have returned? I considered having each callback method increment a variable (using jQuery's data() method, perhaps) and then waiting for the value to become 5. (I am not sure yet how I would listen for that event.) I do not think this is a very good solution, however. What would happen if two calls return at the same time? Is there a better way to do this?

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  • How do I fire an asynchronous call in asp classic and ignore the response?

    - by Hexate
    Here's the gist: I have a call I want to make in asp, and I do not care about the response. I just want to fire the call and I do not want the page to wait for the response. According to the documentation, it should look something like this: dim xmlhttp : set xmlhttp = Server.CreateObject("MSXML2.ServerXMLHTTP") xmlhttp.Open "POST", url, true '' setting the 'asynchronous' option to 'true' xmlhttp.setRequestHeader "Content-Type", "application/soap+xml; charset=utf-8" xmlhttp.setRequestHeader "Content-Length", Len(XMLData) xmlhttp.send XMLData This works peachy when calling synchronously, but when I flip the ansynchronous option to 'true', nothing fires. What I can gather from the internet is that users do something like the following: While xmlhttp.readyState <> 4 xmlhttp.waitForResponse 1000 Wend Am I crazy in that this does not really seem like an asynchrous call anymore though if you are waiting for a response? putting the line xmlhttp.waitForResponse 1 right after the send will cause the request to fire, but again, I don't want to wait a second. Any thoughts?

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  • [C#] How to consume web service adheres to the Event-based Asynchronous Pattern?

    - by codemonkie
    I am following the example from http://msdn.microsoft.com/en-us/library/8wy069k1.aspx to consume a web service implemented (by 3rd party) using the Event-based Asynchronous Pattern. However, my program needs to do multiple calls to the DoStuffAsync() hence will get back as many DoStuffCompleted. I chose the overload which takes an extra parameter - Object userState to distinguish them. My first question is: Is it valid to cast a GUID to Object as below, where GUID is used to generate unique taskID? Object userState = Guid.NewGuid(); Secondly, do I need to spawn off a new thread for each DoStuffAsync() call, since I am calling it multiple times? Also, would be nice to have some online examples or tutorials on this subject. (I've been googling for it the whole day and didn't get much back) Many thanks

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  • Flash: How to get a list to be processed synchronous instead of asynchronous?

    - by Quandary
    Question: In Flash I have the below function. Now the problem is SaveFurniture, SavePolygons and SaveComments all save to the same XML file. Now SaveFurniture sends JSON encoded data to a ashx handler, which saves it in the xml on the server. The problem is, because flash sends the data asynchronous, the polygons get sent to the polygonsave ashx handler, but before saving of the furniture has completed, thus access error, write process already in progress... // cSaveData.SaveData(); public static function SaveData():void { trace("cSaveData.SaveData"); //NotifyASPXofNewScale(cGlobals.nPlanScale); SaveFurniture(); SavePolygons(); SaveComments(); } What's the best way to process this list, ONE AFTER ANOTHER ? Making a callback in all of them does make the program flow structure very confusing...

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  • multi user web game with scheduled processing?

    - by Rooq
    I have an idea for a game which I am in the process of designing, but I am struggling to establish if the way I plan to implement it is possible. The game is a text based sports management simulation. This will require players to take certain actions through a web browser which will interact with a database - adding/updating and selecting. Most of the code required to be executed at this point will be fairly straightforward. The main processing will take place by applications which are scheduled to run on the server at certain times. These apps will process transactions added by the players and also perform some automatic processing based on the game date. My plan was to use an SQL server database (at last count I require about 20 tables) and VB.net for all the coding (coming from a mainframe programming background this language is the simplist for me to get to grips with). I will also need a scheduling tool on the server. Can anyone tell me if what I am planning is feasible before I dive into the actual coding stage of my project?

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  • Installing Oracle Event Processing 11g by Antoney Reynolds

    - by JuergenKress
    Earlier this month I was involved in organizing the Monument Family History Day. It was certainly a complex event, with dozens of presenters, guides and 100s of visitors. So with that experience of a complex event under my belt I decided to refresh my acquaintance with Oracle Event Processing (CEP). CEP has a developer side based on Eclipse and a runtime environment. Server install The server install is very straightforward (documentation). It is recommended to use the JRockit JDK with CEP so the steps to set up a working CEP server environment are: Download required software JRockit - I used Oracle “JRockit 6 - R28.2.5” which includes “JRockit Mission Control 4.1” and “JRockit Real Time 4.1”. Oracle Event Processor - I used “Complex Event Processing Release 11gR1 (11.1.1.6.0)” Install JRockit Run the JRockit installer, the download is an executable binary that just needs to be marked as executable. Install CEP Unzip the downloaded file Run the CEP installer, the unzipped file is an executable binary that may need to be marked as executable. Choose a custom install and add the examples if needed. It is not recommended to add the examples to a production environment but they can be helpful in development. Developer Install The developer install requires several steps (documentation). A developer install needs access to the software for the server install, although JRockit isn’t necessary for development use. Read the full article by Antony Reynolds. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress,CEP,Reynolds

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  • Parallelize incremental processing in Tabular #ssas #tabular

    - by Marco Russo (SQLBI)
    I recently came in a problem trying to improve the parallelism of Tabular processing. As you know, multiple tables can be processed in parallel, whereas the processing of several partitions within the same table cannot be parallelized. When you perform an incremental update by adding only new rows to existing table, what you really do is adding rows to a partition, so adding rows to many tables means adding rows to several partitions. The particular condition you have in this case is that every partition in which you add rows belongs to a different table. Adding rows implies using the ProcessAdd command; its QueryBinding parameter specifies a SQL syntax to read new rows, otherwise the original query specified for the partition will be used, and it could generate duplicated data if you don’t have a dynamic behavior on the SQL side. If you create the required XMLA code manually, you will find that the QueryBinding node that should be part of the ProcessAdd command has to be moved out from ProcessAdd in case you are using a Batch command with more than one Process command (which is the reason why you want to use a single batch: run multiple process operations in parallel!). If you use AMO (Analysis Management Objects) you will find that this combination is not supported, even if you don’t have a syntax error compiling the code, but you might obtain this error at execution time: The syntax for the 'Process' command is incorrect. The 'Bindings' keyword cannot appear under a 'Process' command if the 'Process' command is a part of a 'Batch' command and there are more than one 'Process' commands in the 'Batch' or the 'Batch' command contains any out of line related information. In this case, the 'Bindings' keyword should be a part of the 'Batch' command only. If this is happening to you, the best solution I’ve found is manipulating the XMLA code generated by AMO moving the Binding nodes in the right place. A more detailed description of the issue and the code required to send a correct XMLA batch to Analysis Services is available in my article Parallelize ProcessAdd with AMO. By the way, the same technique (and code) can be used also if you have the same problem in a Multidimensional model.

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  • Command Pattern refactor for input processing?

    - by Casey
    According to Game Coding Complete 4th. ed. processing input via the following is considered unmanagable and inflexible. But does not show an example. I've used the Command pattern to represent GUI button commands but could not figure out how to represent the input from the keyboard and/or mouse. if(g_keyboard->KeyDown(KEY_ESC)) { quit = true; return; } //Processing if(g_keyboard->KeyDown(KEY_T)) { g_show_test_gateway = !g_show_test_gateway; } if(g_mouse->ButtonDown(a2de::Mouse::BUTTON2)) { g_selected_part = GWPart::PART_NONE; SetMouseImageToPartImage(); } ResetButtonStates(); g_prevButton = g_curButton; g_curButton = GetButtonHovered(); if(g_curButton) { g_mouse->SetImageToDefault(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1) || g_mouse->ButtonPress(a2de::Mouse::BUTTON1)) { ButtonPressCommand curCommand(g_curButton); curCommand.Execute(); } else if(g_mouse->ButtonUp(a2de::Mouse::BUTTON1)) { if(g_prevButton == g_curButton) { ButtonReleaseCommand curCommand(g_curButton); curCommand.Execute(); if(g_curButton->GetType() == "export") { ExportCommand curCommand(g_curButton, *g_gateway); curCommand.Execute(); } } else { ResetButtonStates(); } } else { ButtonHoverCommand curCommand(g_curButton); curCommand.Execute(); } } else { g_status_message.clear(); SetMouseImageToPartImage(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1)) { CreatePartCommand curCommand(*g_gateway, g_selected_part, a2de::Vector2D(g_mouse->GetX(), g_mouse->GetY())); curCommand.Execute(); } }

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  • Question regarding Readability vs Processing Time

    - by Jordy
    I am creating a flowchart for a program with multiple sequential steps. Every step should be performed if the previous step is succesful. I use a c-based programming language so the lay-out would be something like this: METHOD 1: if(step_one_succeeded()) { if(step_two_succeeded()) { if(step_three_succeeded()) { //etc. etc. } } } If my program would have 15+ steps, the resulting code would be terribly unfriendly to read. So I changed my design and implemented a global errorcode that I keep passing by reference, make everything more readable. The resulting code would be something like this: METHOD 2: int _no_error = 0; step_one(_no_error); if(_no_error == 0) step_two(_no_error); if(_no_error == 0) step_three(_no_error); if(_no_error == 0) step_two(_no_error); The cyclomatic complexibility stays the same. Now let's say there are N number of steps. And let's assume that checking a condition is 1 clock long and performing a step doesn't take up time. The processing speed of Method1 can be anywhere between 1 and N. The processing speed of Method2 however is always equal to N-1. So Method1 will be faster most of the time. Which brings me to my question, is it bad practice to sacrifice time in order to make the code more readable? And why (not)?

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  • Customizing the processing of ListItems for asp:RadioButtonList with "Flow" layout and "Horizontal"

    - by evovision
    Hi, recently I was asked to add an ability to pad specific elements from each other to a certain distance in RadioButtonList control. Not quite common everyday task I would say :)   Ok, let's get started!   Prerequisites: ASP.NET Page having RadioButtonList control with RepeatLayout="Flow" RepeatDirection="Horizontal" properties set.   Implementation:  The underlying data was coming from another source, so the only fast way to add meta information about padding was the text value itself (yes, not very optimal solution): Id = 1, Name = "This is first element" and for padding we agreed to use <space/> meta tag: Id = 2, Name = "<space padcount="30px"/>This is second padded element"   To handle items rendering in RadioButtonList control I've created custom class and subclassed from it:    public class CustomRadioButtonList : RadioButtonList    {        private Action<ListItem, HtmlTextWriter> _preProcess;         protected override void RenderItem(ListItemType itemType, int repeatIndex, RepeatInfo repeatInfo, HtmlTextWriter writer)        {            if (_preProcess != null)            {                _preProcess(this.Items[repeatIndex], writer);            }             base.RenderItem(itemType, repeatIndex, repeatInfo, writer);        }         public void SetPrePrenderItemFunction(Action<ListItem, HtmlTextWriter> func)        {            _preProcess = func;        }    }   It is pretty straightforward approach, the key is to override RenderItem method. Class has SetPrePrenderItemFunction method which is used to pass custom processing function that takes 2 parameters: ListItem and HtmlTextWriter objects.   Now update existing RadioButtonList control in Default.aspx: add this to beginning of the page:   <%@ Register Namespace="Sample.Controls" TagPrefix="uc1" %>   and update the control to:   <uc1:CustomRadioButtonList ID="customRbl" runat="server" DataValueField="Id" DataTextField="Name"            RepeatLayout="Flow" RepeatDirection="Horizontal"></uc1:CustomRadioButtonList>   Now, from codebehind of the page:   Add regular expression that will be used for parsing:   private Regex _regex = new Regex(@"(?:[<]space padcount\s*?=\s*?(?:'|"")(?<padcount>\d+)(?:(?:\s+)?px)?(?:'|"")\s*?/>)(?<content>.*)?", RegexOptions.IgnoreCase | RegexOptions.Compiled);   and finally setup the processing function in Page_Load:   protected void Page_Load(object sender, EventArgs e)    {        customRbl.DataSource = DataObjects;         customRbl.SetPrePrenderItemFunction((listItem, writer) =>        {            Match match = _regex.Match(listItem.Text);            if (match.Success)            {                writer.Write(string.Format(@"<span style=""padding-left:{0}"">Extreme values: </span>", match.Groups["padcount"].Value + "px"));                 // if you need to pad listitem use code below                //x.Attributes.CssStyle.Add("padding-left", match.Groups["padcount"].Value + "px");                 // remove meta tag from text                listItem.Text = match.Groups["content"].Value;            }        });         customRbl.DataBind();    }   That's it! :)   Run the attached sample application:     P.S.: of course several other approaches could have been used for that purpose including events and the functionality for processing could also be embedded inside control itself. Current solution suits slightly better due some other reasons for situation where it was used, in your case consider this as a kick start for your own implementation :)   Source application: CustomRadioButtonList.zip

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  • Exitus Acta Probat: The Post-Processing Module

    - by Phil Factor
    Sometimes, one has to make certain ethical compromises to ensure the success of a corporate IT project. Exitus Acta Probat (literally 'the result validates the deeds' meaning that the ends justify the means)It was a while back, whilst working as a Technical Architect for a well-known international company, that I was given the task of designing the architecture of a rather specialized accounting system. We'd tried an off-the-shelf (OTS) Windows-based solution which crashed with dispiriting regularity, and didn't quite do what the business required. After a great deal of research and planning, we commissioned a Unux-based system that used X-terminals for the desktops of  the participating staff. X terminals are now obsolete, but were then hot stuff; stripped-down Unix workstations that provided client GUIs for networked applications long before the days of AJAX, Flash, Air and DHTML. I've never known a project go so smoothly: I'd been initially rather nervous about going the Unix route, believing then that  Unix programmers were excitable creatures who were prone to  indulge in role-play enactments of elves and wizards at the weekend, but the programmers I met from the company that did the work seemed to be rather donnish, earnest, people who quickly grasped our requirements and were faultlessly professional in their work.After thinking lofty thoughts for a while, there was considerable pummeling of keyboards by our suppliers, and a beautiful robust application was delivered to us ahead of dates.Soon, the department who had commissioned the work received shiny new X Terminals to replace their rather depressing lavatory-beige PCs. I modestly hung around as the application was commissioned and deployed to the department in order to receive the plaudits. They didn't come. Something was very wrong with the project. I couldn't put my finger on the problem, and the users weren't doing any more than desperately and futilely searching the application to find a fault with it.Many times in my life, I've come up against a predicament like this: The roll-out of an application goes wrong and you are hearing nothing that helps you to discern the cause but nit-*** noise. There is a limit to the emotional heat you can pack into a complaint about text being in the wrong font, or an input form being slightly cramped, but they tried their best. The answer is, of course, one that every IT executive should have tattooed prominently where they can read it in emergencies: In Vino Veritas (literally, 'in wine the truth', alcohol loosens the tongue. A roman proverb) It was time to slap the wallet and get the department down the pub with the tab in my name. It was an eye-watering investment, but hedged with an over-confident IT director who relished my discomfort. To cut a long story short, The real reason gushed out with the third round. We had deprived them of their PCs, which had been good for very little from the pure business perspective, but had provided them with many hours of happiness playing computer-based minesweeper and solitaire. There is no more agreeable way of passing away the interminable hours of wage-slavery than minesweeper or solitaire, and the employees had applauded the munificence of their employer who had provided them with the means to play it. I had, unthinkingly, deprived them of it.I held an emergency meeting with our suppliers the following day. I came over big with the notion that it was in their interests to provide a solution. They played it cool, probably knowing that it was my head on the block, not theirs. In the end, they came up with a compromise. they would temporarily descend from their lofty, cerebral stamping grounds  in order to write a server-based Minesweeper and Solitaire game for X Terminals, and install it in a concealed place within the system. We'd have to pay for it, though. I groaned. How could we do that? "Could we call it a 'post-processing module?" suggested their account executive.And so it came to pass. The application was a resounding success. Every now and then, the staff were able to indulge in some 'post-processing', with what turned out to be a very fine implementation of both minesweeper and solitaire. There were several refinements: A single click in a 'boss' button turned the games into what looked just like a financial spreadsheet.  They even threw in a multi-user version of Battleships. The extra payment for the post-processing module went through the change-control process without anyone untoward noticing, and peace once more descended. Only one thing niggles. Those games were good. Do they still survive, somewhere in a Linux library? If so, I'd like to claim a small part in their production.

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  • Understanding the 'High Performance' meaning in Extreme Transaction Processing

    - by kyap
    Despite my previous blogs entries on SOA/BPM and Identity Management, the domain where I'm the most passionated is definitely the Extreme Transaction Processing, commonly called XTP.I came across XTP back to 2007 while I was still FMW Product Manager in EMEA. At that time Oracle acquired a company called Tangosol, which owned an unique product called Coherence that we renamed to Oracle Coherence. Beside this innovative renaming of the product, to be honest, I didn't know much about it, except being a "distributed in-memory cache for Extreme Transaction Processing"... not very helpful still.In general when people doesn't fully understand a technology or a concept, they tend to find some shortcuts, either correct or not, to justify their lack-of understanding... and of course I was part of this category of individuals. And the shortcut was "Oracle Coherence Cache helps to improve Performance". Excellent marketing slogan... but not very meaningful still. By chance I was able to get away quickly from that group in July 2007* at Thames Valley Park (UK), after I attended one of the most interesting workshops, in my 10 years career in Oracle, delivered by Brian Oliver. The biggest mistake I made was to assume that performance improvement with Coherence was related to the response time. Which can be considered as legitimus at that time, because after-all caches help to reduce latency on cached data access, hence reduce the response-time. But like all caches, you need to define caching and expiration policies, thinking about the cache-missed strategy, and most of the time you have to re-write partially your application in order to work with the cache. At a result, the expected benefit vanishes... so, not very useful then?The key mistake I made was my perception or obsession on how performance improvement should be driven, but I strongly believe this is still a common problem to most of the developers. In fact we all know the that the performance of a system is generally presented by the Capacity (or Throughput), with the 2 important dimensions Speed (response-time) and Volume (load) :Capacity (TPS) = Volume (T) / Speed (S)To increase the Capacity, we can either reduce the Speed(in terms of response-time), or to increase the Volume. However we tend to only focus on reducing the Speed dimension, perhaps it is more concrete and tangible to measure, and nicer to present to our management because there's a direct impact onto the end-users experience. On the other hand, we assume the Volume can be addressed by the underlying hardware or software stack, so if we need more capacity (scale out), we just add more hardware or software. Unfortunately, the reality proves that IT is never as ideal as we assume...The challenge with Speed improvement approach is that it is generally difficult and costly to make things already fast... faster. And by adding Coherence will not necessarily help either. Even though we manage to do so, the Capacity can not increase forever because... the Speed can be influenced by the Volume. For all system, we always have a performance illustration as follow: In all traditional system, the increase of Volume (Transaction) will also increase the Speed (Response-Time) as some point. The reason is simple: most of the time the Application logics were not designed to scale. As an example, if you have a while-loop in your application, it is natural to conceive that parsing 200 entries will require double execution-time compared to 100 entries. If you need to "Speed-up" the execution, you can only upgrade your hardware (scale-up) with faster CPU and/or network to reduce network latency. It is technically limited and economically inefficient. And this is exactly where XTP and Coherence kick in. The primary objective of XTP is about designing applications which can scale-out for increasing the Volume, by applying coding techniques to keep the execution-time as constant as possible, independently of the number of runtime data being manipulated. It is actually not just about having an application running as fast as possible, but about having a much more predictable system, with constant response-time and linearly scale, so we can easily increase throughput by adding more hardwares in parallel. It is in general combined with the Low Latency Programming model, where we tried to optimize the network usage as much as possible, either from the programmatic angle (less network-hoops to complete a task), and/or from a hardware angle (faster network equipments). In this picture, Oracle Coherence can be considered as software-level XTP enabler, via the Distributed-Cache because it can guarantee: - Constant Data Objects access time, independently from the number of Objects and the Coherence Cluster size - Data Objects Distribution by Affinity for in-memory data grouping - In-place Data Processing for parallel executionTo summarize, Oracle Coherence is indeed useful to improve your application performance, just not in the way we commonly think. It's not about the Speed itself, but about the overall Capacity with Extreme Load while keeping consistant Speed. In the future I will keep adding new blog entries around this topic, with some sample codes experiences sharing that I capture in the last few years. In the meanwhile if you want to know more how Oracle Coherence, I strongly suggest you to start with checking how our worldwide customers are using Oracle Coherence first, then you can start playing with the product through our tutorial.Have Fun !

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  • Force Postback from code behind? Or reload JavaScript from an Asynchronous Postback?

    - by sah302
    Hi all, I've got a Jquery UI dialog that pops up to confirm the creation of an item after filling out a form. I have the form in an update panel due to various needs of the form, and especially because I want validation being done on the form without reloading the page. JavaScript appears to not reload on an asynchronoous postback. This means when the form is a success and I change the variable 'formSubmitPass' to true, it does not get passed to the Javascript via <%= formSubmitPass %. If I add a trigger to the submit button to do a full postback, it works. However I don't want the submit button to do a full postback as I said so I can validate the form within the update panel. How can I have this so my form validates asynchronously, but my javaScript will properly reload when the form is completed successfully and the item is saved to the database? Javascript: var formSubmitPass = '<%= formSubmitPass %>'; var redirectUrl = '<%= redirectUrl %>'; function pageLoad() { $('#formPassBox').dialog({ autoOpen: false, width: 400, resizable: false, modal: true, draggable: false, buttons: { "Ok": function() { window.location.href = redirectUrl; } }, open: function(event, ui) { $(".ui-dialog-titlebar-close").hide(); var t = window.setTimeout("goToUrl()", 5000); } }); if(formSubmitPass == 'True') { $('#formPassBox').dialog({ autoOpen: true }); } So how can I force a postback from the code behind, or reload the JavaScript on an Asynchronous Postback, or do this in a way that will work such that I can continue to do Async form validation? Edit: I change formSubmitPass at the very end of the code behind: If errorCount = 0 Then formSubmitPass = True upForm.Update() Else formSubmitPass = False End If So on a full postback, the value does change.

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  • Why does using the Asynchronous Programming Model in .Net not lead to StackOverflow exceptions?

    - by uriDium
    For example, we call BeginReceive and have the callback method that BeginReceive executes when it has completed. If that callback method once again calls BeginReceive in my mind it would be very similar to recursion. How is that this does not cause a stackoverflow exception. Example code from MSDN: private static void Receive(Socket client) { try { // Create the state object. StateObject state = new StateObject(); state.workSocket = client; // Begin receiving the data from the remote device. client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReceiveCallback), state); } catch (Exception e) { Console.WriteLine(e.ToString()); } } private static void ReceiveCallback( IAsyncResult ar ) { try { // Retrieve the state object and the client socket // from the asynchronous state object. StateObject state = (StateObject) ar.AsyncState; Socket client = state.workSocket; // Read data from the remote device. int bytesRead = client.EndReceive(ar); if (bytesRead > 0) { // There might be more data, so store the data received so far. state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,bytesRead)); // Get the rest of the data. client.BeginReceive(state.buffer,0,StateObject.BufferSize,0, new AsyncCallback(ReceiveCallback), state); } else { // All the data has arrived; put it in response. if (state.sb.Length > 1) { response = state.sb.ToString(); } // Signal that all bytes have been received. receiveDone.Set(); } } catch (Exception e) { Console.WriteLine(e.ToString()); } }

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  • Which way is preferred when doing asynchronous WCF calls?

    - by Mikael Svenson
    When invoking a WCF service asynchronous there seems to be two ways it can be done. 1. public void One() { WcfClient client = new WcfClient(); client.BegindoSearch("input", ResultOne, null); } private void ResultOne(IAsyncResult ar) { WcfClient client = new WcfClient(); string data = client.EnddoSearch(ar); } 2. public void Two() { WcfClient client = new WcfClient(); client.doSearchCompleted += TwoCompleted; client.doSearchAsync("input"); } void TwoCompleted(object sender, doSearchCompletedEventArgs e) { string data = e.Result; } And with the new Task<T> class we have an easy third way by wrapping the synchronous operation in a task. 3. public void Three() { WcfClient client = new WcfClient(); var task = Task<string>.Factory.StartNew(() => client.doSearch("input")); string data = task.Result; } They all give you the ability to execute other code while you wait for the result, but I think Task<T> gives better control on what you execute before or after the result is retrieved. Are there any advantages or disadvantages to using one over the other? Or scenarios where one way of doing it is more preferable?

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  • How can I make a WPF TreeView data binding lazy and asynchronous?

    - by pauldoo
    I am learning how to use data binding in WPF for a TreeView. I am procedurally creating the Binding object, setting Source, Path, and Converter properties to point to my own classes. I can even go as far as setting IsAsync and I can see the GUI update asynchronously when I explore the tree. So far so good! My problem is that WPF eagerly evaluates parts of the tree prior to them being expanded in the GUI. If left long enough this would result in the entire tree being evaluated (well actually in this example my tree is infinite, but you get the idea). I would like the tree only be evaluated on demand as the user expands the nodes. Is this possible using the existing asynchronous data binding stuff in the WPF? As an aside I have not figured out how ObjectDataProvider relates to this task. My XAML code contains only a single TreeView object, and my C# code is: public partial class Window1 : Window { public Window1() { InitializeComponent(); treeView.Items.Add( CreateItem(2) ); } static TreeViewItem CreateItem(int number) { TreeViewItem item = new TreeViewItem(); item.Header = number; Binding b = new Binding(); b.Converter = new MyConverter(); b.Source = new MyDataProvider(number); b.Path = new PropertyPath("Value"); b.IsAsync = true; item.SetBinding(TreeView.ItemsSourceProperty, b); return item; } class MyDataProvider { readonly int m_value; public MyDataProvider(int value) { m_value = value; } public int[] Value { get { // Sleep to mimick a costly operation that should not hang the UI System.Threading.Thread.Sleep(2000); System.Diagnostics.Debug.Write(string.Format("Evaluated for {0}\n", m_value)); return new int[] { m_value * 2, m_value + 1, }; } } } class MyConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { // Convert the double to an int. int[] values = (int[])value; IList<TreeViewItem> result = new List<TreeViewItem>(); foreach (int i in values) { result.Add(CreateItem(i)); } return result; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new InvalidOperationException("Not implemented."); } } } Note: I have previously managed to do lazy evaluation of the tree nodes by adding WPF event handlers and directly adding items when the event handlers are triggered. I'm trying to move away from that and use data binding instead (which I understand is more in spirit with "the WPF way").

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  • Ubuntu 10.04 - unable to install Arduino

    - by Newbie
    Hello! At the moment, I try to install Arduino on my Ubuntu 10.04 (32 Bit) computer. I downloaded the latest release at http://arduino.cc/en/Main/Software, cd'ed to the directory and unziped the package. When I try to run ./arduino , I get following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Base.main(Base.java:112) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(Unknown Source) ... 1 more Here is my java -version output: java version "1.6.0_20" OpenJDK Runtime Environment (IcedTea6 1.9.5) (6b20-1.9.5-0ubuntu1~10.04.1) OpenJDK Server VM (build 19.0-b09, mixed mode) Any suggestions on this? I try to install arduino without the 'arduino' package. I tried to install it with apt-get (sudo apt-get install arduino). When I try to start arduino (using arduino command) will cause following error: Exception in thread "main" java.lang.ExceptionInInitializerError at processing.app.Preferences.load(Preferences.java:553) at processing.app.Preferences.load(Preferences.java:549) at processing.app.Preferences.init(Preferences.java:142) at processing.app.Base.main(Base.java:188) Caused by: java.awt.HeadlessException at sun.awt.HeadlessToolkit.getMenuShortcutKeyMask(HeadlessToolkit.java:231) at processing.core.PApplet.<clinit>(PApplet.java:224) ... 4 more Update: I saw that I installed several versions of jre (sun and open). So I uninstalled the open jre. Now, when calling arduino I get a new error: java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1734) at java.lang.Runtime.loadLibrary0(Runtime.java:823) at java.lang.System.loadLibrary(System.java:1028) at gnu.io.CommPortIdentifier.<clinit>(CommPortIdentifier.java:123) at processing.app.Editor.populateSerialMenu(Editor.java:965) at processing.app.Editor.buildToolsMenu(Editor.java:717) at processing.app.Editor.buildMenuBar(Editor.java:502) at processing.app.Editor.<init>(Editor.java:194) at processing.app.Base.handleOpen(Base.java:698) at processing.app.Base.handleOpen(Base.java:663) at processing.app.Base.handleNew(Base.java:578) at processing.app.Base.<init>(Base.java:318) at processing.app.Base.main(Base.java:207)

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  • ADO.NET Data Services business logic processing

    a simple approach that provides business logic processing before forwarding data to the clients with ADO.NET Data Services.  read moreBy Siyamand AyubiDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • .NET processing unit [closed]

    - by configurator
    Do you think we'll ever see an IL (or other bytecode) processing unit? It sounds possible and would have a major benefit, because we wouldn't need the JITter. This isn't the same as compiling .NET directly to machine code, since the bytecode here is designed to be programmed and disassembled easily, unlike the bytecode used in x86 processors which is designed to work faster. What's stopping Intel (for example) from partnering with Microsoft and making such a .NET-optimised processor?

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  • What is stopping data flow with .NET 3.5 asynchronous System.Net.Sockets.Socket?

    - by TonyG
    I have a .NET 3.5 client/server socket interface using the asynchronous methods. The client connects to the server and the connection should remain open until the app terminates. The protocol consists of the following pattern: send stx receive ack send data1 receive ack send data2 (repeat 5-6 while more data) receive ack send etx So a single transaction with two datablocks as above would consist of 4 sends from the client. After sending etx the client simply waits for more data to send out, then begins the next transmission with stx. I do not want to break the connection between individual exchanges or after each stx/data/etx payload. Right now, after connection, the client can send the first stx, and get a single ack, but I can't put more data onto the wire after that. Neither side disconnects, the socket is still intact. The client code is seriously abbreviated as follows - I'm following the pattern commonly available in online code samples. private void SendReceive(string data) { // ... SocketAsyncEventArgs completeArgs; completeArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnSend); clientSocket.SendAsync(completeArgs); // two AutoResetEvents, one for send, one for receive if ( !AutoResetEvent.WaitAll(autoSendReceiveEvents , -1) ) Log("failed"); else Log("success"); // ... } private void OnSend( object sender , SocketAsyncEventArgs e ) { // ... Socket s = e.UserToken as Socket; byte[] receiveBuffer = new byte[ 4096 ]; e.SetBuffer(receiveBuffer , 0 , receiveBuffer.Length); e.Completed += new EventHandler<SocketAsyncEventArgs>(OnReceive); s.ReceiveAsync(e); // ... } private void OnReceive( object sender , SocketAsyncEventArgs e ) {} // ... if ( e.BytesTransferred > 0 ) { Int32 bytesTransferred = e.BytesTransferred; String received = Encoding.ASCII.GetString(e.Buffer , e.Offset , bytesTransferred); dataReceived += received; } autoSendReceiveEvents[ SendOperation ].Set(); // could be moved elsewhere autoSendReceiveEvents[ ReceiveOperation ].Set(); // releases mutexes } The code on the server is very similar except that it receives first and then sends a response - the server is not doing anything (that I can tell) to modify the connection after it sends a response. The problem is that the second time I hit SendReceive in the client, the connection is already in a weird state. Do I need to do something in the client to preserve the SocketAsyncEventArgs, and re-use the same object for the lifetime of the socket/connection? I'm not sure which eventargs object should hang around during the life of the connection or a given exchange. Do I need to do something, or Not do something in the server to ensure it continues to Receive data? The server setup and response processing looks like this: void Start() { // ... listenSocket.Bind(...); listenSocket.Listen(0); StartAccept(null); // note accept as soon as we start. OK? mutex.WaitOne(); } void StartAccept(SocketAsyncEventArgs acceptEventArg) { if ( acceptEventArg == null ) { acceptEventArg = new SocketAsyncEventArgs(); acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(OnAcceptCompleted); } Boolean willRaiseEvent = this.listenSocket.AcceptAsync(acceptEventArg); if ( !willRaiseEvent ) ProcessAccept(acceptEventArg); // ... } private void OnAcceptCompleted( object sender , SocketAsyncEventArgs e ) { ProcessAccept(e); } private void ProcessAccept( SocketAsyncEventArgs e ) { // ... SocketAsyncEventArgs readEventArgs = new SocketAsyncEventArgs(); readEventArgs.SetBuffer(dataBuffer , 0 , Int16.MaxValue); readEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnIOCompleted); readEventArgs.UserToken = e.AcceptSocket; dataReceived = ""; // note server is degraded for single client/thread use // As soon as the client is connected, post a receive to the connection. Boolean willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs); if ( !willRaiseEvent ) this.ProcessReceive(readEventArgs); // Accept the next connection request. this.StartAccept(e); } private void OnIOCompleted( object sender , SocketAsyncEventArgs e ) { // switch ( e.LastOperation ) case SocketAsyncOperation.Receive: ProcessReceive(e); // similar to client code // operate on dataReceived here case SocketAsyncOperation.Send: ProcessSend(e); // similar to client code } // execute this when a data has been processed into a response (ack, etc) private SendResponseToClient(string response) { // create buffer with response // currentEventArgs has class scope and is re-used currentEventArgs.SetBuffer(sendBuffer , 0 , sendBuffer.Length); Boolean willRaiseEvent = currentClient.SendAsync(currentEventArgs); if ( !willRaiseEvent ) ProcessSend(currentEventArgs); } A .NET trace shows the following when sending ABC\r\n: Socket#7588182::SendAsync() Socket#7588182::SendAsync(True#1) Data from Socket#7588182::FinishOperation(SendAsync) 00000000 : 41 42 43 0D 0A Socket#7588182::ReceiveAsync() Exiting Socket#7588182::ReceiveAsync() - True#1 And it stops there. It looks just like the first send from the client but the server shows no activity. I think that could be info overload for now but I'll be happy to provide more details as required. Thanks!

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  • Design For Asynchronous User Interface

    - by Sohnee
    I have been working on a integration that has posed an interesting user interface conundrum that I would like suggestions for. The user interface is displayed within a third party product. The state of the interface is supplied by calls to a service I have written. There can be small delays between the actual state changing the the user interface changing due to the polling for state by the third party. When a user interacts with the user interface, requests are sent back to my application. This then affects the state and the next state poll request will update the user interface. The problem is that the delay between pressing a button and seeing the user interface update is perhaps 1 or 2 seconds and in usability testing I can see that people are clicking again before the user interface updates, thinking that they haven't properly clicked the first time. Given the constraints (we can only update the user interface via the polling mechanism - if we updated it when they clicked, the polling might return and overwrite the change causing unpredictable / undesirable results)... what can we do to make the user experience better. My current idea is to show a message for a couple of seconds so people know their click was accepted, the message would not be affected by the state polling, so wouldn't be prematurely removed / overwritten etc. I'm sure there are other ideas out there and I'm also confident someone has a better idea that I have!

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