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• Upload large files via a webpage

  - by Hultner

  What way is the best way to let users upload large files from there webbrowser to a server. I'm talking 200MB+ possible up to a few gigatyes. I have been thinking of a few possible solutions to the problem (not tried them yet) and this is basically the things I came up with. Server download speed will not be a problem but the users connection possibly could. Having some sort of applet on the client side written in Java or Flash which sends the file in parts (is this possible with an applet) to a php/other script on the server and a checksum+ some other info about the file. On the server scripts all the parts and the info file is saved in a temporary directory wich has a unique name based on the checksum of the file and the ip of the user. When the last chunk is sent the applet sends a signal to the server saying it's finished and the server put the file together in the right location. If a chunk doesn't match the checksum for that part the server will send a response to the applet telling it to reupload that chunk. I don't know how important the checksum checking is since it's all tcpackages, someone with more insigth migth be able to answer on that. This is probably the worst way, changing the settings on your server to allow huge fileuploads via an inputfiel. Do it like a normal transfer. User an uploadmanager which does pretty much the same thing as applet i mentioned above. Pros of the first is probably that it would most likely be rather secure, you could show progress as well and possibly resume an upload if ip hasn't changed and do a threaded upload of the chunks. Cons of the first is that the user will need flash/java for it to work. Pros of the 2nd is that it will pretty much work for everyone but cons are big, first there's no way resuming an intruppted download and if something is wrong the whole file would have to be reuploaded is a few of cons. For the third one the pros is pretty muc the same as for the first but the cons is that the user would have to download an application to their computer and run and the application will have to be have to be compatible with their computer and OS. Another way may be a combination of two. Lets say an applet for bigger or more files and a simple input which is rather restricted to maybe max 10-20MB for smaller files and comability. There are probably other much smarter ways to tackle this and that's why I'm asking for advice here on SO.

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• Flex - Problem with auto resizing datagrid

  - by Marty Pitt

  Hi All I'm trying to create a datagrid which will resize vertically to ensure all the renderers are displayed in full. Additionally, Renderers are of variable height Renderers can resize themselves Generally speaking, the flow of events is as follows : One of the item renderers resizes itself (normally in response to a user click etc) It dispatches a bubbling event which the parent datagrid picks up The DataGrid attempts to resize to ensure that all renderers remain visible in full. I'm currently using this code within the datagrid to calculate the height: height = measureHeightOfItems(0, dataProvider.length ) + headerHeight; This appears to get an incorrect height. I've tried a number of variations including callLater ( to ensure the resize has completed so measure can work correctly), and overriding meausre() and calling invalidateSize() / validateSize(), but neither works. Below are 3 classes which will illustrate the problem. Clicking the button in the item renderers resizes the renderer. The grid should also expand so that all of the 3 renderers are shown in their entirety. Any suggestions would be greatly appreciated. Regards Marty DataGridProblem.mxml (Application file) <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="vertical" xmlns:view="view.*"> <mx:ArrayCollection id="dataProvider"> <mx:String>Item A</mx:String> <mx:String>Item B</mx:String> <mx:String>Item C</mx:String> </mx:ArrayCollection> <view:TestDataGrid id="dg" dataProvider="{ dataProvider }" width="400"> <view:columns> <mx:DataGridColumn dataField="text" /> <mx:DataGridColumn itemRenderer="view.RendererButton" /> </view:columns> </view:TestDataGrid> </mx:Application> view.TestDataGrid.as package view { import flash.events.Event; import mx.controls.DataGrid; import mx.core.ScrollPolicy; public class TestDataGrid extends DataGrid { public function TestDataGrid() { this.verticalScrollPolicy = ScrollPolicy.OFF; this.variableRowHeight = true; this.addEventListener( RendererButton.RENDERER_RESIZE , onRendererResize ); } private function onRendererResize( event : Event ) : void { resizeDatagrid(); } private function resizeDatagrid():void { height = measureHeightOfItems(0, dataProvider.length ) + headerHeight; } } } view.RendererButton.mxml <?xml version="1.0" encoding="utf-8"?> <mx:HBox xmlns:mx="http://www.adobe.com/2006/mxml"> <mx:Button width="50" height="50" click="onClick()" /> <mx:Script> <![CDATA[ public static const RENDERER_RESIZE : String = "resizeRenderer"; private function onClick() : void { this.height += 20; dispatchEvent( new Event( RENDERER_RESIZE , true ) ); } ]]> </mx:Script> </mx:HBox>

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• javascript select box hanging on second select in ie7

  - by bsandrabr

  I have a drop down select box inside a div. When the user clicks on change, a dropdown box appears next to the change/submit button and the user makes a selection which then updates the db and the selection appears instead of the dropdown. All works fine in IE8 and firefox but in IE7 it allows one selection (there are several identical dropdowns) but the second time a selection is made it hangs on please wait. This is the relevant code <td width=200> <input type="button" onclick="startChanging(this)" value="Change" /></td> <script type="text/javascript"> var selectBox, isEditing = false; var recordvalue; if( window.XMLHttpRequest ) { recordvalue = new XMLHttpRequest(); } else if( window.ActiveXObject ) { try { recordvalue = new ActiveXObject('Microsoft.XMLHTTP'); } catch(e) {} } window.onload = function () { selectBox = document.getElementById('changer'); selectBox.id = ''; selectBox.parentNode.removeChild(selectBox); }; function startChanging(whatButton) { if( isEditing && isEditing != whatButton ) { return; } //no editing of other entries if( isEditing == whatButton ) { changeSelect(whatButton); return; } //this time, act as "submit" isEditing = whatButton; whatButton.value = 'Submit'; var theRow = whatButton.parentNode.parentNode; var stateCell = theRow.cells[3]; //the cell that says "present" stateCell.className = 'editing'; //so you can use CSS to remove the background colour stateCell.replaceChild(selectBox,stateCell.firstChild); //PRESENT is replaced with the select input selectBox.selectedIndex = 0; } function changeSelect(whatButton) { isEditing = true; //don't allow it to be clicked until submission is complete whatButton.value = 'Change'; var stateCell = selectBox.parentNode; var theRow = stateCell.parentNode; var editid = theRow.cells[0].firstChild.firstChild.nodeValue; //text inside the first cell var value = selectBox.firstChild.options[selectBox.firstChild.selectedIndex].value; //the option they chose selectBox.parentNode.replaceChild(document.createTextNode('Please wait...'),selectBox); if( !recordvalue ) { //allow fallback to basic HTTP location.href = 'getupdate.php?id='+editid+'&newvalue='+value; } else { recordvalue.onreadystatechange = function () { if( recordvalue.readyState != 4 ) { return; } if( recordvalue.status >= 300 ) { alert('An error occurred when trying to update'); } isEditing = false; newState = recordvalue.responseText.split("|"); stateCell.className = newState[0]; stateCell.firstChild.nodeValue = newState[1] || 'Server response was not correct'; }; recordvalue.open('GET', "getupdate.php?id="+editid+"&newvalue="+value, true); recordvalue.send(null); } } </script> If anyone has any idea why this is happening I'd be very grateful

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• How to embed html table into the bpdy of email

  - by Michael Mao

  Hi all: I am sending info to target email via PHP native mail() method right now. Everything else works fine but the table part troubles me the most. See sample output : Dear Michael Mao : Thank you for purchasing flight tickets with us, here is your receipt : Your tickets will be delivered by mail to the following address : Street Address 1 : sdfsdafsadf sdf Street Address 2 : N/A City : Sydney State : nsw Postcode : 2 Country : Australia Credit Card Number : *************1234 Your purchase details are recorded as : <table><tr><th class="delete">del?</th><th class="from_city">from</th><th class="to_city">to</th><th class="quantity">qty</th><th class="price">unit price</th><th class="price">total price</th></tr><tr class="evenrow" id="Sydney-Lima"><td><input name="isDeleting" type="checkbox"></td><td>Sydney</td><td>Lima</td><td>1</td><td>1030.00</td><td>1030</td></tr><tr class="oddrow" id="Sydney-Perth"><td><input name="isDeleting" type="checkbox"></td><td>Sydney</td><td>Perth</td><td>3</td><td>340.00</td><td>1020</td></tr><tr class="totalprice"><td colspan="5">Grand Total Price</td><td id="grandtotal">2050</td></tr></table> The source of table is directly taken from a webpage, exactly as the same. However, Gmail, Hotmail and most of other emails will ignore to render this as a table. So I am wondering, without using Outlook or other email sending agent software, how could I craft a embedded table for the PHP mail() method to send? Current code snippet corresponds to table generation : $purchaseinfo = $_POST["purchaseinfo"]; //if html tags are not to be filtered in the body of email $stringBuilder .= "<table>" .stripslashes($purchaseinfo) ."</table>"; //must send json response back to caller ajax request if(mail($email, 'Your purchase information on www.hardlyworldtravel.com', $emailbody, $headers)) echo json_encode(array("feedback"=>"successful")); else echo json_encode(array("feedback"=>"error")); Any hints and suggestions are welcomed, thanks a lot in advance.

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• GUI Application becomes unresponsive while http request is being done

  - by JW

  I have just made my first proper little desktop GUI application that basically wraps a GUI (php-gtk) interface around a SimpleTest Web Test case to make it act as a remote testing client. Each time the local The Web Test case runs, it sends an HTTP request to another SimpleTest case (that has an XHTML interface) sitting on my server. The application, allows me to run one local test that collates information from multiple remote tests. It just has a 'Start Test' button, 'Stop Test' button and a setting to increase/decrease the number of remote tests conducted in each HTTP Request. Each test-run takes about an hour to complete. The trouble is, most of the time the application is making http requests. Furthermore, whenever an HTTP Request is being made, the application's GUI is unresponsive. I have taken to making the application wait a few seconds (iterating through the Gtk::main_iteration ) between requests in order to give the user time to re-size the window, press the Stop button, etc. But, this makes the whole test run take a lot a longer than is necessary. <?php require_once('simpletest/web_tester.php'); class TestRemoteTestingClient extends WebTestCase { function testRunIterations() { ... $this->assertTrue($this->get($nextUrl), 'getting from pointer:'. $this->_remoteMementoPointer); $this->assertResponse(200, "checking response for " . $nextUrl ); $this->assertText('RemoteNodeGreen'); $this->doGtkIterationsForMinNSeconds($secs); ... } public function doGtkIterationsForMinNSeconds($secs) { $this->appendStatusMessage("Waiting " . $secs); $start = time(); $end = $start + $secs; while( (time() < $end) ) { $this->appendStatusMessage("Waiting " . ($end - time())); while(gtk::events_pending()) Gtk::main_iteration(); } } } Is there a way to keep the application responsive whilst, at the same time making an HTTP request? I am considering splitting the application into two, where: Test Controller Application - Acts as a settings-writer / report-reader and this writes to settings file and reads a report file. Test Runner Application - Acts as a settings-reader / report-writer and, for each iteration reads the settings file, Runs the test, then write a report. So to tell it to close down - I'd: Press the Stop Button on the 'Test Controller Application', which writes to the settings file, which is read by the 'Test Runner Application' which stops, then writes to the report file to say it stopped the 'Test Controller Application' reads the report and updates the status and so on... However, before I go ahead and split the application in two - I am wondering if there is any other obvious way to deal with, this issue. I suspect it is probably quite common and a well-trodden path. Also is there an easier way to send messages between two applications?

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• ASP.NET Web Service - how to handle special characters in strings?

  - by Vlorg

  To show this fundamental issue in .NET and the reason for this question, I have written a simple test web service with one method (EditString), and a consumer console app that calls it. They are both standard web service/console applications created via File/New Project, etc., so I won't list the whole code - just the methods in question: Web method: [WebMethod] public string EditString(string s, bool useSpecial) { return s + (useSpecial ? ((char)19).ToString() : ""); } [You can see it simply returns the string s if useSpecial is false. If useSpecial is true, it returns s + char 19.] Console app: TestService.Service1 service = new SCTestConsumer.TestService.Service1(); string response1 = service.EditString("hello", false); Console.WriteLine(response1); string response2 = service.EditString("hello", true); // fails! Console.WriteLine(response2); [The second response fails, because the method returns hello + a special character (ascii code 19 for argument's sake).] The error is: There is an error in XML document (1, 287) Inner exception: "'', hexadecimal value 0x13, is an invalid character. Line 1, position 287." A few points worth mentioning: The web method itself WORKS FINE when browsing directly to the ASMX file (e.g. http://localhost:2065/service1.asmx), and running the method through this (with the same parameters as in the console application) - i.e. displays XML with the string hello + char 19. Checking the serialized XML in other ways shows the special character is being encoded properly (the SERVER SIDE seems to be ok which is GOOD) So it seems the CLIENT SIDE has the issue - i.e. the .NET generated proxy class code doesn't handle special characters This is part of a bigger project where objects are passed in and out of the web methods - that contain string attributes - these are what need to work properly. i.e. we're de/serializing classes. Any suggestions for a workaround and how to implement it? Or have I completely missed something really obvious!!? Thanks in advance... PS. I've not had much luck with getting it to use CDATA tags (does .NET support these out of the box?).

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• A Python Wrapper for Shutterfly. Uploading an Image

  - by iJames

  I'm working on a Django app in which I want to order prints through Shutterfly's Open API: http://www.shutterfly.com/documentation/start.sfly So far I've been able to build the appropriate POSTs and GETs using the modules and suggested code snippets including httplib, httplib2, urllib, urllib2, mimetype, etc. But I'm stuck on the image uploading when placing an order (the ordering process is not the same process as uploading images to albums which I haven't tried.) From what I can tell, I'm supposed to basically create the multipart form data by concatenating the HTTP request body together with the binary data of the image. I take the strings: --myuniqueboundary1273149960.175.1 Content-Disposition: form-data; name="AuthenticationID" auniqueauthenticationid --myuniqueboundary1273149960.175.1 Content-Disposition: file; name="Image.Data"; filename="1_41_orig.jpg" Content-Type: image/jpeg and I put this data into it and end with the final boundary: ...\xb5|\xf88\x1dj\t@\xd9\'\x1f\xc6j\x88{\x8a\xc0\x18\x8eGaJG\x03\xe9J-\xd8\x96[\x91T\xc3\x0eTu\xf4\xaa\xa5Ty\x80\x01\x8c\x9f\xe9Z\xad\x8cg\xba# g\x18\xe2\xaa:\x829\x02\xb4["\x17Q\xe7\x801\xea?\xad7j\xfd\xa2\xdf\x81\xd2\x84D\xb6)\xa8\xcb\xc8O\\\x9a\xaf(\x1cqM\x98\x8d*\xb8\'h\xc8+\x8e:u\xaa\xf3*\x9b\x95\x05F8\xedN%\xcb\xe1B2\xa9~Tw\xedF\xc4\xfe\xe8\xfc\xa9\x983\xff\xd9... That ends up making it look like this (when I use print to debug): ... --myuniqueboundary1273149960.175.1 Content-Disposition: file; name="Image.Data"; filename="1_41_orig.jpg" Content-Type: image/jpeg ????q?ExifMM* ? ??(1?2?<??i?b?NIKON CORPORATIONNIKON D40HHQuickTime 7.62009:02:17 13:05:25Mac OS X 10.5.6%??????"?'??0220?????? ???? ? ?|_???,b???50??5 ... --myuniqueboundary1273149960.175.1-- My code for grabbing the binary data is pretty much this: filedata = open('myjpegfile.jpeg','rb').read() Which I then add to the rest of the body. I've see something like this code everywhere. I'm then using this to post the full request (with the headers too): response = urllib2.urlopen(request).read() This seems to me to be the standard way that form POSTS with files happens. Am I missing something here? At some point I might be able to make this into a library worth posting up on github, but this problem has stopped me cold in my tracks. Thanks for any insight!

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• Connected host failed to respond (internal NAT address)

  - by MostRandom

  I'm writing my first C# web application that connects to an XML based service. It requires that I present a certificate and feed the XML stream. It seems to authenticate properly but then it gives the following error: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.1.10.4:3128 The funny thing is that I'm not on a proxy or anything like that. I'm connecting directly to the internet. At one point I we did use a proxy that with internal NAT address. So my question is: Does Visual Studio have some sort of default proxy setting that I need to change? This IP is no longer used for anything, so I know that I don't need to use any proxy authentication code. using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Net; using System.Security.Cryptography.X509Certificates; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; namespace WebApplication1 { public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Uri requestURI = new Uri("*site omitted*"); //Create the Request Object HttpWebRequest pageRequest = (HttpWebRequest)WebRequest.Create(requestURI); //After installing the cert on the server export a client cert to the working directory as Deluxe.cer string certFile = "*certificate omitted*"; X509Certificate cert = X509Certificate.CreateFromCertFile(certFile); //Pull in your Data, if it is from an external xml as below or create an xml string with variables if a dynamic post is required. string xmlPath = "*XML omitted*"; System.Xml.XmlDocument passXML = new System.Xml.XmlDocument(); passXML.Load(xmlPath); //XML String with the data needed to pass string postData = passXML.OuterXml; //Set the Request Object parameters pageRequest.ContentType = "application/x-www-form-urlencoded"; pageRequest.Method = "POST"; pageRequest.AllowWriteStreamBuffering = false; pageRequest.AllowAutoRedirect = false; pageRequest.ClientCertificates.Add(cert); postData = "xml_data=" + Server.UrlEncode(postData); pageRequest.ContentLength = postData.Length; //Create the Post Stream Object System.IO.StreamWriter postStream = new System.IO.StreamWriter(pageRequest.GetRequestStream()); //Write the data to the post stream postStream.Write(postData); postStream.Flush(); postStream.Close(); //Set the Response Object HttpWebResponse postResponse = (HttpWebResponse)pageRequest.GetResponse();

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• How can I import one Gradle script into another?

  - by Ant

  Hi all, I have a complex gradle script that wraps up a load of functionality around building and deploying a number of netbeans projects to a number of environments. The script works very well, but in essence it is all configured through half a dozen maps holding project and environment information. I want to abstract the tasks away into another file, so that I can simply define my maps in a simple build file, and import the tasks from the other file. In this way, I can use the same core tasks for a number of projects and configure those projects with a simple set of maps. Can anyone tell me how I can import one gradle file into another, in a similar manner to Ant's task? I've trawled Gradle's docs to no avail so far. Additional Info After Tom's response below, I thought I'd try and clarify exactly what I mean. Basically I have a gradle script which runs a number of subprojects. However, the subprojects are all Netbeans projects, and come with their own ant build scripts, so I have tasks in gradle to call each of these. My problem is that I have some configuration at the top of the file, such as: projects = [ [name:"MySubproject1", shortname: "sub1", env:"mainEnv", cvs_module="mod1"], [name:"MySubproject2", shortname: "sub2", env:"altEnv", cvs_module="mod2"] ] I then generate tasks such as: projects.each({ task "checkout_$it.shortname" << { // Code to for example check module out from cvs using config from 'it'. } }) I have many of these sort of task generation snippets, and all of them are generic - they entirely depend on the config in the projects list. So what I want is a way to put this in a separate script and import it in the following sort of way: projects = [ [name:"MySubproject1", shortname: "sub1", env:"mainEnv", cvs_module="mod1"], [name:"MySubproject2", shortname: "sub2", env:"altEnv", cvs_module="mod2"] ] import("tasks.gradle") // This will import and run the script so that all tasks are generated for the projects given above. So in this example, tasks.gradle will have all the generic task generation code in, and will get run for the projects defined in the main build.gradle file. In this way, tasks.gradle is a file that can be used by all large projects that consist of a number of sub-projects with Netbeans ant build files.

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• Adding OutputCache to an ASP.NET WebForm crashes my site :(

  - by Pure.Krome

  Hi folks, When I add either one of these ... <%@ OutputCache Duration="600" Location="Any" VaryByParam="*" %> or <%@ OutputCache CacheProfile="CmsArticlesListOrItem" %> (.. and this into the web.config file...) <caching> <outputCacheSettings> <outputCacheProfiles> <add name="CmsArticlesListOrItem" duration="600" varyByParam="*" /> </outputCacheProfiles> </outputCacheSettings> <sqlCacheDependency ........ ></sqlCacheDependency </caching> my page/site crashes with the following error:- Source: System.Web ---------------------------------------------------------------------------- TargetSite: System.Web.DirectoryMonitor FindDirectoryMonitor(System.String, Boolean, Boolean) ---------------------------------------------------------------------------- Message:System.Web.HttpException: Directory 'C:\Web Sites\My Site Foo - Main Site\Controls\InfoAdvice' does not exist. Failed to start monitoring file changes. at System.Web.FileChangesMonitor.FindDirectoryMonitor(String dir, Boolean addIfNotFound, Boolean throwOnError) at System.Web.FileChangesMonitor.StartMonitoringPath(String alias, FileChangeEventHandler callback, FileAttributesData& fad) at System.Web.Caching.CacheDependency.Init(Boolean isPublic, String[] filenamesArg, String[] cachekeysArg, CacheDependency dependency, DateTime utcStart) at System.Web.Caching.CacheDependency..ctor(Int32 dummy, String[] filenames, DateTime utcStart) at System.Web.Hosting.MapPathBasedVirtualPathProvider.GetCacheDependency(String virtualPath, IEnumerable virtualPathDependencies, DateTime utcStart) at System.Web.ResponseDependencyList.CreateCacheDependency(CacheDependencyType dependencyType, CacheDependency dependency) at System.Web.HttpResponse.CreateCacheDependencyForResponse(CacheDependency dependencyVary) at System.Web.Caching.OutputCacheModule.InsertResponse(HttpResponse response, HttpContext context, String keyRawResponse, HttpCachePolicySettings settings, CachedVary cachedVary, CachedRawResponse memoryRawResponse) at System.Web.Caching.OutputCacheModule.OnLeave(Object source, EventArgs eventArgs) at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) Ok .. so for some reason, the OutputCache wants a folder/file to be there? Well, i've had this site live for around 3 years and i'm pretty sure that the folders \Controls and \Controls\InfoAdvice doesn't exist on my production server. On my localhost, it sure does .. and contains a large list of ascx controls. But they don't exist on my live server. So ... what is going on here? Can anyone please help? Oh :) Before someone suggests I create those two folders and even stick a random file in those folders .. and have some random text in those random files .. i've done that and it doesn't seem to work, still :( Please Help !

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• Linked List Design

  - by Jim Scott

  The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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• mysql_connect() causes page to not display (WAMP)

  - by VOIDHand

  I currently have a website running MySQL and PHP in which this is all working. I've tried installing WAMPServer to be able to work on the site on my own computer, but I have been having issues trying to get the site to work correctly. HTML and PHP files work correctly (by going to http://localhost/index.php, etc.). But some of the pages display "This Webpage is not available" (in Chrome) or "Internet Explorer cannot display this webpage", which leads me to think there is an error is the server, as when the page doesn't exist, it typically dispays "Oops! This link appears to be broken" or IE's standard 404 page. Each page in my site has an include() call to set up an instance of a class to handle all database transactions. This class opens the connection to the database in its constructor. I have found commenting out the contents of the constructor will allow the page to load, although this understandably causes errors later in the page. This is the contents of the included file: class dbAccess { private $db; function __construct() { $this->db = mysql_connect("externalURL","user","password") or die ("Connection for database not found."); mysql_select_db("dbName", $this->db) or die ("Database not selected"); } ... } As a note for what's happening here. I'm attempting to use the database on my site, rather than the local machine. The actual values of externalURL, dbName, user, and password work when I plug them into my database software and the file fine of the site, so I don't think the issue is with those values themselves, but rather some setting with Apache or Wamp. The issue persists if I try a local database as well. This is an excerpt of my Apache error log for one attempt at logging into the site: [Wed Apr 14 15:32:54 2010] [notice] Parent: child process exited with status 255 -- Restarting. [Wed Apr 14 15:32:54 2010] [notice] Apache/2.2.11 (Win32) PHP/5.3.0 configured -- resuming normal operations [Wed Apr 14 15:32:54 2010] [notice] Server built: Dec 10 2008 00:10:06 [Wed Apr 14 15:32:54 2010] [notice] Parent: Created child process 1756 [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Child process is running [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Acquired the start mutex. [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Starting 64 worker threads. [Wed Apr 14 15:32:55 2010] [notice] Child 1756: Starting thread to listen on port 80. For the first line, isLoggedIn (from the first line) is a method of the class above. Assuming that the connection works, this error should disappear. I've tried searching for solutions online, but haven't been able to find anything to help. If you need any further information to help solve this issue, feel free to ask for it. (One more note, I don't even have Skype on this computer, so I can't see it being an issue, as this conflict seems to be the default response for any Wamp issue.) [Edit: Removed entry from the error log as it was solved as an unrelated issue]

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• Rails: AJAX Controller JS not firing...

  - by neezer

  I'm having an issue with one of my controller's AJAX functionality. Here's what I have: class PhotosController < ApplicationController # ... def create @photo = Photo.new(params[:photo]) @photo.image_content_type = MIME::Types.type_for(@photo.image_file_name).to_s @photo.image_width = Paperclip::Geometry.from_file(params[:photo][:image]).width.to_i @photo.image_height = Paperclip::Geometry.from_file(params[:photo][:image]).height.to_i @photo.save! respond_to do |format| format.js end end # ... end This is called through a POST request sent by this code: $(function() { // add photos link $('a.add-photos-link').colorbox({ overlayClose: false, onComplete: function() { wire_add_photo_modal(); } }); function wire_add_photo_modal() { <% session_key = ActionController::Base.session_options[:key] %> $('#upload_photo').uploadify({ uploader: '/swf/uploadify.swf', script: '/photos', cancelImg: '/images/buttons/cancel.png', buttonText: 'Upload Photo(s)', auto: true, queueID: 'queue', fileDataName: 'photo[image]', scriptData: { '<%= session_key %>': '<%= u cookies[session_key] %>', commit: 'Adding Photo', controller: 'photos', action: 'create', '_method': 'post', 'photo[gallery_id]': $('#gallery_id').val(), 'photo[user_id]': $('#user_id').val(), authenticity_token: encodeURIComponent('<%= u form_authenticity_token if protect_against_forgery? %>') }, multi: true }); } }); Finally, I have my response code in app/views/photos/create.js.erb: alert('photo added!'); My log file shows that the request was successful (the photo was successfully uploaded), and it even says that it rendered the create action, yet I never get the alert. My browser shows NO javascript errors. Here's the log AFTER a request from the above POST request is submitted: Processing PhotosController#create (for 127.0.0.1 at 2010-03-16 14:35:33) [POST] Parameters: {"Filename"=>"tumblr_kx74k06IuI1qzt6cxo1_400.jpg", "photo"=>{"user_id"=>"1", "image"=>#<File:/tmp/RackMultipart20100316-54303-7r2npu-0>}, "commit"=>"Adding Photo", "_edited_session"=>"edited", "folder"=>"/kakagiloon/", "authenticity_token"=>"edited", "action"=>"create", "_method"=>"post", "Upload"=>"Submit Query", "controller"=>"photos"} [paperclip] Saving attachments. [paperclip] saving /public/images/assets/kakagiloon/thumbnail/tumblr_kx74k06IuI1qzt6cxo1_400.jpg [paperclip] saving /public/images/assets/kakagiloon/profile/tumblr_kx74k06IuI1qzt6cxo1_400.jpg [paperclip] saving /public/images/assets/kakagiloon/original/tumblr_kx74k06IuI1qzt6cxo1_400.jpg Rendering photos/create Completed in 248ms (View: 1, DB: 6) | 200 OK [http://edited.local/photos] NOTE: I edited out all the SQL statements and I put "edited" in place of sensitive info. What gives? Why aren't I getting my alert();? Please let me know if you need anymore info to help me solve this issue! Thanks.

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• Decode the string encoded through php in javascript

  - by Pankaj Khurana

  Hi, I am working on a facebook page in which i have used ajax & response is returned in json format. I have encoded the string in php. Now i want to decode that string in javascript. foreach($feedbackdetails as $feedbackdetail) { $str.= '<div class="tweet"> <img style="cursor:pointer;" id="imgVoteUp" src="http://myserver/facebook/vote_up.gif" alt="Vote Up" title="Vote Up" onclick="saveVote('.$feedbackdetail[pk_feedbackid].',1)" /> : '.$feedbackdetail[upvotecount].' <img style="cursor:pointer;" id="imgVoteDown" src="http://myserver/facebook/vote_down.gif" alt="Vote Down" title="Vote Down" onclick="saveVote('.$feedbackdetail[pk_feedbackid].',0)" /> : '.$feedbackdetail[downvotecount].' <p class="'.$pclass.'">'.$feedbackdetail[title].' by '.$feedbackdetail[name].'<br>'.$feedbackdetail[description].'</p></div>'; } $str=urlencode($str); echo '{"fbml_test":"'.$str.'"}'; Javascript Function: function saveVote(id,type,class) { contentdiv='div_'+id; processdiv='processdiv_'+id; document.getElementById(processdiv).setInnerXHTML('<span id="caric"><center><img src="http://static.ak.fbcdn.net/rsrc.php/z5R48/hash/ejut8v2y.gif" /></center></span>'); posturl='http://myserver/facebook/vote.php'; if(class==0) { class='firstmessage'; } else { class='message'; } var queryString = "?id="+id+"&type="+type+"&pclass="+class; posturl = posturl +queryString; ajax = new Ajax(); ajax.responseType = Ajax.JSON; ajax.requireLogin = true; ajax.ondone = function(data) { document.getElementById('caric').setStyle('display','none'); //new Dialog().showMessage('Dialog',data); if(data.error) { new Dialog().showMessage('Dialog',data.error); } if(data.fbml_test) { document.getElementById(contentdiv).setInnerFBML(data)); } //div_id.setInnerFBML(data); } ajax.post(posturl); } Right now i am getting encoded string how can i change it? Please help me on this Thanks Pankaj

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• Show loading image when pdf rendering

  - by Pankaj

  I am displaying pdf on my page like this <object data="/Customer/GetPricedMaterialPDF?projID=<%= ViewData["ProjectID"]%>" type="application/pdf" width="960" height="900" style="margin-top: -33px;"> <p> It appears you don't have a PDF plugin for this browser. No biggie... you can <a href="/Customer/GetPricedMaterialPDF?projID=<%= ViewData["ProjectID"]%>">click here to download the PDF file. </a> </p> </object> and Controller function are public FileStreamResult GetPricedMaterialPDF(string projID) { System.IO.Stream fileStream = GeneratePDF(projID); HttpContext.Response.AddHeader("content-disposition", "attachment; filename=form.pdf"); return new FileStreamResult(fileStream, "application/pdf"); } private System.IO.Stream GeneratePDF(string projID) { //create your pdf and put it into the stream... pdf variable below //comes from a class I use to write content to PDF files System.IO.MemoryStream ms = new System.IO.MemoryStream(); Project proj = GetProject(projID); List<File> ff = proj.GetFiles(Project_Thin.Folders.IntegrationFiles, true); string fileName = string.Empty; if (ff != null && ff.Count > 0 && ff.Where(p => p.AccessToUserID == CurrentCustomer.CustomerID).Count() > 0) { ff = ff.Where(p => p.AccessToUserID == CurrentCustomer.CustomerID).ToList(); foreach (var item in ff) { fileName = item.FileName; } byte[] bArr = new byte[] { }; bArr = GetJDLFile(fileName); ms.Write(bArr, 0, bArr.Length); ms.Position = 0; } return ms; } Now my problem is function on controller taking 10 to 20 second to process pdf, data="/Customer/GetPricedMaterialPDF?projID=<%= ViewData["ProjectID"]%>" at that time my page shows blank, which i don't want. i want to show loading image at that time. How can i do this...

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• Asynchronous Silverlight 4 call to the World of Warcraft armoury streaming XML in C#

  - by user348446

  Hello - I have been stuck on this all weekend and failed miserably! Please help me to claw back my sanity!! Your challenge For my first Silverlight application I thought it would be fun to use the World of Warcraft armoury to list the characters in my guild. This involves making an asyncronous from Silverlight (duh!) to the WoW armoury which is XML based. SIMPLE EH? Take a look at this link and open the source. You'll see what I mean: http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented Below is code for getting the XML (the call to ShowGuildies will cope with the returned XML - I have tested this locally and I know it works). I have not managed to get the expected returned XML at all. Notes: If the browser is capable of transforming the XML it will do so, otherwise HTML will be provided. I think it examines the UserAgent I am a seasoned asp.net web developer C# so go easy if you start talking about native to Windows Forms / WPF I can't seem to set the UserAgent setting in .net 4.0 - doesn't seem to be a property off the HttpWebRequest object for some reason - i think it used to be available. Silverlight 4.0 (created as 3.0 originally before I updated my installation of Silverlight to 4.0) Created using C# 4.0 Please explain as if you talking to a web developer and not a proper programming lol! Below is the code - it should return the XML from the wow armoury. private void button7_Click(object sender, RoutedEventArgs e) { // URL for armoury lookup string url = @"http://eu.wowarmory.com/guild-info.xml?r=Eonar&n=Gifted and Talented"; // Create the web request HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url); // Set the user agent so we are returned XML and not HTML //httpWebRequest.Headers["User-Agent"] = "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0)"; // Not sure about this dispatcher thing - it's late so i have started to guess. Dispatcher.BeginInvoke(delegate() { // Call asyncronously IAsyncResult asyncResult = httpWebRequest.BeginGetResponse(ReqCallback, httpWebRequest); // End the response and use the result using (HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.EndGetResponse(asyncResult)) { // Load an XML document from a stream XDocument x = XDocument.Load(httpWebResponse.GetResponseStream()); // Basic function that will use LINQ to XML to get the list of characters. ShowGuildies(x); } }); } private void ReqCallback(IAsyncResult asynchronousResult) { // Not sure what to do here - maybe update the interface? } Really hope someone out there can help me! Thanks mucho! Dan. PS Yes, I have noticed the irony in the name of the guild :)

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• Joomla - Force File Download / CSV Export

  - by lautaro.dragan

  I'm in need of help... this is my first time asking a question in SO, so please be kind :) I'm trying to force-download a file from php, so when the user hits a certain button, he gets a file download. The file is a csv (email, username) of all registered users. I decided to add this button to the admin users screen, as you can see in this screenshot. So I added the following code to the addToolbar function in administrator/components/com_users/views/users/view.html.php: JToolBarHelper::custom('users.export', 'export.png', 'export_f2.png', 'Exportar', false); This button is mapped to the following function in the com_users\controller\users.php controller: public function exportAllUsers() { ob_end_clean(); $app = JFactory::getApplication(); header("Content-type: text/csv"); header("Content-Disposition: attachment; filename=ideary_users.csv"); header("Pragma: no-cache"); header("Expires: 0"); echo "email,name\n"; $model = $this->getModel("Users"); $users = $model->getAllUsers(); foreach ($users as $user) { echo $user->email . ", " . ucwords(trim($user->name)) . "\r\n"; } $app->close(); } Now, this is actually working perfectly fine. The issue here is that after I download a file, if I hit any button in the admin that causes a POST, instead of it performing the action it should, it just downloads the file over again! For example: I hit the "Export" button "users.csv" downloads Then, I hit the "search" button "users.csv" downloads... what the hell? I'm guessing that when I hit the export button, a JS gets called and sets a form's action attribute to an URL... and expects a response or something, and then other button's are prevented from re-setting the form's action attribute. I can't think of any real solution for this, but I'd rather avoid hacks if possible. So, what would be the standard, elegant solution that joomla offers in this case?

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• need to get the context value in top of page, where the context value will be set only at the bottom

  - by Mahadevan Alagar

  <script runat="server"> protected void Page_Load(object sender, EventArgs e) { Response.Write("Page Load:"); } public string setContext(string sName, string sVal) { HttpContext.Current.Items[sName] = sVal; return sVal; } public string getContext(string sName) { string sVal = "default"; if (HttpContext.Current.Items[sName] != null) sVal = HttpContext.Current.Items[sName].ToString(); else sVal = "empty"; return sVal; } </script> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Get Context in TOP ???</title> </head> <body> <div> <div id="divDest" name="divDest"> Top Content: Get1 :<%= getContext("topcontent") %> // returns "empty", BUT I Need "value to set" </div> <br /> Set1 : <%= setContext("topcontent", "value to set")%> <br /> // set the value <br /> Get2 : <%= getContext("topcontent") %><br /> // returns "value to set" <br /> <script language="javascript"> var elval = getElementVal("divTest"); document.getElementById("divDest").innerHTML = elval; //alert(elval); function getElementVal(elemid) { var elemval = document.getElementById(elemid); return elemval.innerHTML; } </script> </body> </html> I need to get the context value in top of page, where the context value will be set at the bottom of the page. Get context value == "empty", BUT need "something" Set context value to "something" Get context value == "something" I may use JS/AJAX, where the page source the value won't be present. BUT I need the TEXT in the View Source of the page too. Is there a way to wait for the context to set and then get, I have tried with User Control, prerender and render methods too. But I can't able to get it right. Any idea?

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• jquery ajax post callback - manipulation stops after the "third" call

  - by shanyu

  EDIT: The problem is not related to Boxy, I've run into the same issue when I've used JQuery 's load method. EDIT 2: When I take out link.remove() from inside the ajax callback and place it before ajax load, the problem is no more. Are there restrictions for manipulating elements inside an ajax callback function. I am using JQuery with Boxy plugin. When the 'Flag' link on the page is clicked, a Boxy modal pops-up and loads a form via ajax. When the user submits the form, the link (<a> tag) is removed and a new one is created from the ajax response. This mechanism works for, well, 3 times! After the 3rd, the callback function just does not remove/replace/append (tested several variations of manipulation) the element. The only hint I have is that after the 3rd call, the parent of the link becomes non-selectable. However I can't make anything of this. Sorry if this is a very trivial issue, I have no experience in client-side programming. The relevant html is below: <div class="flag-link"> <img class="flag-img" style="width: 16px; visibility: hidden;" src="/static/images/flag.png" alt=""/> <a class="unflagged" href="/i/flag/showform/9/1/?next=/users/1/ozgurisil">Flag</a> </div> Here is the relevant js code: $(document).ready(function() { $('div.flag-link a.unflagged').live('click', function(e){ doFlag(e); return false; }); ... }); function doFlag(e) { var link = $(e.target); var url = link.attr('href'); Boxy.load(url, {title:'Inappropriate Content', unloadOnHide:true, cache:false, behaviours: function(r) { $("#flag-form").live("submit", function(){ var post_url = $("#flag-form").attr('action'); boxy = Boxy.get(this); boxy.hideAndUnload(); $.post(post_url, $("#flag-form").serialize(), function(data){ par = link.parent(); par.append(data); alert (par.attr('class')); //BECOMES UNDEFINED AT THE 3RD CALL!! par.children('img.flag-img').css('visibility', 'visible'); link.remove(); }); return false; }); }}); }

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• casting, converting, and input from textbox controls

  - by Matt

  Working on some .aspx.cs code and decided I would forget how to turn a textbox value into a useable integer or decimal. Be warned I'm pretty new to .asp. Wish I could say the same for c sharp. So the value going into my textbox (strawberryp_textbox) is "1" which I presume I can access with the .text property. Which I then parse into a int. The Error reads Format Exception was unhandled by user code. My other question is can I do operations on a session variable? protected void submit_order_button_Click(object sender, EventArgs e) { int strawberryp; int strawberrys; decimal money1 = decimal.Parse(moneybox1.Text); decimal money2 = decimal.Parse(moneybox2.Text); decimal money3 = decimal.Parse(moneybox3.Text); decimal money4 = decimal.Parse(moneybox4.Text); decimal money5 = decimal.Parse(moneybox5.Text); strawberryp = int.Parse(strawberryp_Textbox.Text); //THE PROBLEM RIGHT HERE! strawberrys = int.Parse(strawberrys_Textbox.Text); // Needs fixed int strawberryc = int.Parse(strawberryc_Textbox.Text); //fix int berryp = int.Parse(berryp_Textbox.Text); //fix int raspberryp = int.Parse(raspberryp_Textbox.Text); /fix decimal subtotal = (money1 * strawberryp) + (money2 * strawberrys) + (money3 * strawberryc) + (money4 * berryp) + (money5 * raspberryp); //check to see if you can multiply decimal and int to get a deciaml!! Session["passmysubtotal"] = subtotal; //TextBox2.Text; (strawberryp_Textbox.Text);//TextBox4.Text; add_my_order_button.Enabled = true; add_my_order_button.Visible = true; submit_order_button.Enabled = false; submit_order_button.Visible = false; strawberryp_Textbox.ReadOnly = false; strawberrys_Textbox.ReadOnly = false; strawberryc_Textbox.ReadOnly = false; berryp_Textbox.ReadOnly = false; raspberryp_Textbox.ReadOnly = false; Response.Redirect("reciept.aspx"); } Thanks for the help

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• jQuery multiple running totals

  - by Benjamin Randal

  0I am using jQuery to calculate a running total on multiple textboxes. Just found an awesome response on how to get that working a few days ago, but now I am running into another problem. When using one selector, the total for GetTotal is calculated perfectly. However, when I include the second selector, the totals begin to conflict with one another, and no longer calculate properly. I have been searching for a solution to this for some time now, does anyone have any ideas? Here is the selector i am currently using: function GetTotal(txtBox) { var total = 0; $('input:text').each(function(index, value) { total += parseInt($(value).val() || 0); }); $("#chkTotal").html(total); } My view uses these txt boxes <div class="editor-field"> @Html.TextBox("Field1", String.Empty, new {InputType = "text", id = "field1", onchange = "GetTotal(this)" }) </div> <div class="editor-field"> @Html.TextBox("Field2", String.Empty, new {InputType = "text", id = "field2", onchange = "GetTotal(this)" }) </div> <div> <h3>Total Checked</h3> </div> <div id="chkTotal"></div> Now I am trying to implement another selector which will total two additional editor fields... function GetTotal1(txtBox) { var total1 = 0; $('input:text').each(function (index, value) { total1 += parseInt($(value).val() || 0); }); $("#disTotal").html(total1); } View: <div class="editor-field"> @Html.TextBox("Field3", String.Empty, new {InputType = "text", id = "field3", onchange = "GetTotal1(this)" }) </div> <div class="editor-field"> @Html.TextBox("Field4", String.Empty, new {InputType = "text", id = "field4", onchange = "GetTotal1(this)" }) </div> <div> <h3>Total Distributed</h3> </div> <div id="disTotal"></div>

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• No output from Linq to XML

  - by Gogster

  Hi all, I have the following code: protected void Page_Load(object sender, EventArgs e) { XElement xml = XElement.Load(Server.MapPath("ArenasMembers.xml")); var query = from p in xml.Descendants("members") select new { Name = p.Element("name").Value, Email = p.Attribute("email").Value }; foreach (var member in query) { Response.Write("Employee: " + member.Name + " " + member.Email + "<br />"); } } Which, using the hover information in Visual Studio, is reading the XNL file in correctly, however the foreach is not outputting any of the records. XML: <?xml version="1.0" encoding="utf-8" ?> <members> <member> <arena>EAA Office</arena> <memberid>1</memberid> <name>Jane Doe</name> <email>[email protected]</email> </member> <member> <arena>EAA Office</arena> <memberid>2</memberid> <name>John Bull</name> <email>[email protected]</email> </member> <member> <arena>O2 Arena</arena> <memberid>3</memberid> <name>John Doe</name> <email>[email protected]</email> </member> <member> <arena>O2 Arena</arena> <memberid>4</memberid> <name>Bernard Cribbins</name> <email>[email protected]</email> </member> <member> <arena>Colourline Arena</arena> <memberid>5</memberid> <name>John Bon Jovi</name> <email>[email protected]</email> </member> <member> <arena>NIA</arena> <memberid>6</memberid> <name>Rhianna</name> <email>[email protected]</email> </member> </members> Can you see what is wrong?

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• How does this Singleton-like web class persists session data, even though session is not updated in

  - by Micah Burnett

  Ok, I've got this singleton-like web class which uses session to maintain state. I initially thought I was going to have to manipulate the session variables on each "set" so that the new values were updated in the session. However I tried using it as-is, and somehow, it remembers state. For example, if run this code on one page: UserContext.Current.User.FirstName = "Micah"; And run this code in a different browser tab, FirstName is displayed correctly: Response.Write(UserContext.Current.User.FirstName); Can someone tell me (prove) how this data is getting persisted in the session? Here is the class: using System; using System.Collections.Generic; using System.Linq; using System.Web; public class UserContext { private UserContext() { } public static UserContext Current { get { if (System.Web.HttpContext.Current.Session["UserContext"] == null) { UserContext uc = new UserContext(); uc.User = new User(); System.Web.HttpContext.Current.Session["UserContext"] = uc; } return (UserContext)System.Web.HttpContext.Current.Session["UserContext"]; } } private string HospitalField; public string Hospital { get { return HospitalField; } set { HospitalField = value; ContractField = null; ModelType = null; } } private string ContractField; public string Contract { get { return ContractField; } set { ContractField = value; ModelType = string.Empty; } } private string ModelTypeField; public string ModelType { get { return ModelTypeField; } set { ModelTypeField = value; } } private User UserField; public User User { get { return UserField; } set { UserField = value; } } public void DoSomething() { } } public class User { public int UserId { get; set; } public string FirstName { get; set; } } I added this to a watch, and can see that the session variable is definitely being set somewhere: (UserContext)System.Web.HttpContext.Current.Session["UserContext"]; As soon as a setter is called the Session var is immediately updated: set { HospitalField = value; //<--- here ContractField = null; ModelType = null; }

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• Java multiple connections downloading file

  - by weulerjunior

  Hello friends, I was wanting to add multiple connections in the code below to be able to download files faster. Could someone help me? Thanks in advance. public void run() { RandomAccessFile file = null; InputStream stream = null; try { // Open connection to URL. HttpURLConnection connection = (HttpURLConnection) url.openConnection(); // Specify what portion of file to download. connection.setRequestProperty("Range", "bytes=" + downloaded + "-"); // Connect to server. connection.connect(); // Make sure response code is in the 200 range. if (connection.getResponseCode() / 100 != 2) { error(); } // Check for valid content length. int contentLength = connection.getContentLength(); if (contentLength < 1) { error(); } /* Set the size for this download if it hasn't been already set. */ if (size == -1) { size = contentLength; stateChanged(); } // Open file and seek to the end of it. file = new RandomAccessFile("C:\\"+getFileName(url), "rw"); file.seek(downloaded); stream = connection.getInputStream(); while (status == DOWNLOADING) { /* Size buffer according to how much of the file is left to download. */ byte buffer[]; if (size - downloaded > MAX_BUFFER_SIZE) { buffer = new byte[MAX_BUFFER_SIZE]; } else { buffer = new byte[size - downloaded]; } // Read from server into buffer. int read = stream.read(buffer); if (read == -1) { break; } // Write buffer to file. file.write(buffer, 0, read); downloaded += read; stateChanged(); } /* Change status to complete if this point was reached because downloading has finished. */ if (status == DOWNLOADING) { status = COMPLETE; stateChanged(); } } catch (Exception e) { error(); } finally { // Close file. if (file != null) { try { file.close(); } catch (Exception e) { } } // Close connection to server. if (stream != null) { try { stream.close(); } catch (Exception e) { } } } }

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• Persistent (purely functional) Red-Black trees on disk performance

  - by Waneck

  I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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