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• Visual Studio hangs when deploying a cube

  - by Richie

  Hello All, I'm having an issue with an Analysis Services project in Visual Studio 2005. My project always builds but only occasionally deploys. No errors are reported and VS just hangs. This is my first Analysis Services project so I am hoping that there is something obvious that I am just missing. Here is the situation I have a cube that I have successfully deployed. I then make some change, e.g., adding a hierarchy to a dimension. When I try to deploy again VS hangs. I have to restart Analysis Services to regain control of VS so I can shut it down. I restart everything sometimes once, sometimes twice or more before the project will eventually deploy. This happens with any change I make there seems to be no pattern to this behaviour. Sometimes I have to delete the cube from Analysis Services before restarting everything to get a successful deploy. Also I have successfully deployed the cube, and then subsequently successfully reprocessed a dimension then when I open a query window in SQL Server Management Studio it says that it can find any cubes. As a test I have deployed a cube successfully. I have then deleted it in Analysis Services and attempted to redeploy it, without making any changes to the cube, only to have the same behaviour mentioned above. VS just hangs with no reason so I have no idea where to start hunting down the problem. It is taking 15-20 minutes to make a change as simple as setting the NameColumn of a dimension attribute. As you can imagine this is taking hours of my time so I would greatly appreciate any assistance anyone can give me.

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• Is Work Stealing always the most appropriate user-level thread scheduling algorithm?

  - by Il-Bhima

  I've been investigating different scheduling algorithms for a thread pool I am implementing. Due to the nature of the problem I am solving I can assume that the tasks being run in parallel are independent and do not spawn any new tasks. The tasks can be of varying sizes. I went immediately for the most popular scheduling algorithm "work stealing" using lock-free deques for the local job queues, and I am relatively happy with this approach. However I'm wondering whether there are any common cases where work-stealing is not the best approach. For this particular problem I have a good estimate of the size of each individual task. Work-stealing does not make use of this information and I'm wondering if there is any scheduler which will give better load-balancing than work-stealing with this information (obviously with the same efficiency). NB. This question ties up with a previous question.

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• Career day in kindergarten

  - by Péter Török

  I was invited to the kindergarten group of my elder daughter to talk and answer the kids' questions about my profession. There are 26 kids of age 4-6 in the group, plus 3 teachers who are fairly scared of anything related to programming and IT themselves, but bold enough to learn new tricks. I would have about 20-30 minutes, without projector or anything. They have an old computer though, which by its look may be a 486, and I am not even sure if it's functioning. My research turned up excellent earlier threads, with lots of good tips: How would you explain your job to a 5-year old? Career Day: how do I make “computer programmer” sound cool to 8 year olds? What things can I teach a group of children about programming in one day? My situation is different from each of the above though: the latter ones are concerned with older children, while the first one is about talking to a single kid (or elder person)—a group of 20 is a whole different challenge. How can I teach the kids and their teachers about programming in a fun way?

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• Firefox, prevent rendering between javascript statements.

  - by Erik

  I'm trying to create some kind of zoom around the mouse cursor feature on my website which ultimately runs these two lines (+ the same for height/scrollTop). canvas.style.width = someValue; canvas.parentNode.scrollLeft = someOtherValue; The problem is that in firefox(3.6) the page is re-rendered directly after the first row has been executed and since the view is depending on both values this means that every time i recalculate the view firefox will will render an invalid view before the correct one, in other words creating flicker. I've tried swapping the two rows but get the same problem. In chrome, opera and IE this doesn't happen. Both lines are executed before any rendering is done. Is there any way to lock the rendering manually, maybe something like this? document.disableRendering(); //fantasy function canvas.style.width = someValue; canvas.parentNode.scrollLeft = someOtherValue; document.enableRendering(); //fantasy function

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• List of Big-O for PHP functions?

  - by Kendall Hopkins

  After using PHP for a while now, I've noticed that not all PHP built in functions as fast as expected. Consider the below two possible implementations of a function that finds if a number is prime using a cached array of primes. //very slow for large $prime_array $prime_array = array( 2, 3, 5, 7, 11, 13, .... 104729, ... ); $result_array = array(); foreach( $array_of_number => $number ) { $result_array[$number] = in_array( $number, $large_prime_array ); } //still decent performance for large $prime_array $prime_array => array( 2 => NULL, 3 => NULL, 5 => NULL, 7 => NULL, 11 => NULL, 13 => NULL, .... 104729 => NULL, ... ); foreach( $array_of_number => $number ) { $result_array[$number] = array_key_exists( $number, $large_prime_array ); } This is because in_array is implemented with a linear search O(n) which will linearly slow down as $prime_array grows. Where the array_key_exists function is implemented with a hash lookup O(1) which will not slow down unless the hash table gets extremely populated (in which case it's only O(logn)). So far I've had to discover the big-O's via trial and error, and occasionally looking at the source code. Now for the question... I was wondering if there was a list of the theoretical (or practical) big O times for all* the PHP built in functions. *or at least the interesting ones For example find it very hard to predict what the big O of functions listed because the possible implementation depends on unknown core data structures of PHP: array_merge, array_merge_recursive, array_reverse, array_intersect, array_combine, str_replace (with array inputs), etc.

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• Loading default value in a dropdown and calling onchange event

  - by J. Davidson

  Hi i have following dropdown <div class="fcolumn"> <label class="text" for="o_Id">Months:</label> <select class="textMonths" id="o_Id" name="periodName" > <option value="000">Select Period--</option> </select> </div> In the following jquery, first it loads fnLoadP() in a drop down list. Than as a default I am loading one of the values in drop down which is '10'. It loads too as default value. But it should be executing $("#o_Id").change.. which it doesn't. $(document).ready(function () { var sProfileUserId = null; $("#o_Id").change(function () { //---- }); fnLoadP(); $("select[name='pName']").val('10'); }); }); Basically my goal is. After dropdown values are loaded, to load '10' as default value and call onchange event in the dom. Please let me know how to fix it.

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• prototype findElements querySelectorAll error

  - by JD

  i'm call the "down" function but am getting an invalid argument using 1.6.1_rc2 here's the html snippet: <TR id=000000214A class="activeRow searchResultsDisplayOver" conceptID="0000001KIU"> <TD> <DIV class=gridRowWrapper> <SPAN class=SynDesc>Asymmetric breasts</SPAN> <DIV class=buttonWrapper> <SPAN class=btnAddFav title="Add to Favorites">&nbsp;</SPAN> </DIV> </DIV> </TD> </TR> here's the code: var description = row.down('span.SynDesc').innerHTML; row is a dom reference to the element. prototype is appending a # then the id of the element: findElements: function(root) { root = root || document; var e = this.expression, results; switch (this.mode) { case 'selectorsAPI': if (root !== document) { var oldId = root.id, id = $(root).identify(); id = id.replace(/[\.:]/g, "\\$0"); e = "#" + id + " " + e; } results = $A(root.querySelectorAll(e)).map(Element.extend); <-- e = "#000000214A span.SynDesc" root.id = oldId; return results; case 'xpath': return document._getElementsByXPath(this.xpath, root); default: return this.matcher(root); } i get an "invalid argument" error? if i put a breakpoint before the offending line and change e to be equal to "span.SynDesc" it works fine. help. :)

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• Stop scrolling to ID when opening jQuery Modal via URL

  - by markedup

  I need to be able to open an ID'd jQuery UI Modal on a page when that modal's ID is passed in the page's URL. For example: http://mysite.com/visit.html#directions #directions is an ID'd DIV at the very bottom of the page, right before the closing BODY element. It's instantiated as a jQuery UI dialog on page load, then I'm running a function to check the current URL for the modal's ID. If the URL contains the modal's ID, the modal is opened. Here's what my auto-open function looks like: function autoOpenModal() { if ( document.location.href.indexOf('#') ) { var uriParts = document.location.href.split('#'); var hashID = '#' + uriParts[1]; if ( $(hashID) && $(hashID).hasClass('dialog')) { $(hashID).dialog('open'); } } } The problem I'm having is that the browser is automatically scrolling down to the ID at the very bottom of the page before the modal is opened. So when the user closes the modal they're at the bottom of the page (which seems "broken" to me). Can anyone tell me how I stop the browser from auto-scrolling down to the ID please? I've had a look at event.preventDefault() but without success; I'm not sure where or how to use it in the event chain.

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• Singleton constructor question

  - by gillyb

  Hi, I created a Singleton class in c#, with a public property that I want to initialize when the Singleton is first called. This is the code I wrote : public class BL { private ISessionFactory _sessionFactory; public ISessionFactory SessionFactory { get { return _sessionFactory; } set { _sessionFactory = value; } } private BL() { SessionFactory = Dal.SessionFactory.CreateSessionFactory(); } private object thisLock = new object(); private BL _instance = null; public BL Instance { get { lock (thisLock) { if (_instance == null) { _instance = new BL(); } return _instance; } } } } As far as I know, when I address the Instance BL object in the BL class for the first time, it should load the constructor and that should initialize the SessionFactory object. But when I try : BL.Instance.SessionFactory.OpenSession(); I get a Null Reference Exception, and I see that SessionFactory is null... why?

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• Is this ISession handled by the SessionScope - Castle ActiveRecord

  - by oillio

  Can I do this? I have the following in my code: public class ARClass : ActiveRecordBase<ARClass> { ---SNIP--- public void DoStuff() { using (new SessionScope()) { holder.CreateSession(typeof(ARClass)).Lock(this, LockMode.None); ...Do some work... } } } So, as I'm sure you can guess, I am doing this so that I can access lazy loaded references in the object. It works great, however I am worried about creating an ISession like this and just dropping it. Does it get properly registered with the SessionScope and will the scope properly tare my ISession down when it is disposed of? Or do I need to do more to manage it myself?

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• What is the benefit of using ONLY OpenID authentication on a site?

  - by Peter

  From my experience with OpenID, I see a number of significant downsides: Adds a Single Point of Failure to the site It is not a failure that can be fixed by the site even if detected. If the OpenID provider is down for three days, what recourse does the site have to allow its users to login and access the information they own? Takes a user to another sites content and every time they logon to your site Even if the OpenID provider does not have an error, the user is re-directed to their site to login. The login page has content and links. So there is a chance a user will actually be drawn away from the site to go down the Internet rabbit hole. Why would I want to send my users to another company's website? [ Note: my provider no longer does this and seems to have fixed this problem (for now).] Adds a non-trivial amount of time to the signup To sign up with the site a new user is forced to read a new standard, chose a provider, and signup. Standards are something that the technical people should agree to in order to make a user experience frictionless. They are not something that should be thrust on the users. It is a Phisher's Dream OpenID is incredibly insecure and stealing the person's ID as they log in is trivially easy. [ taken from David Arno's Answer below ] For all of the downside, the one upside is to allow users to have fewer logins on the Internet. If a site has opt-in for OpenID then users who want that feature can use it. What I would like to understand is: What benefit does a site get for making OpenID mandatory?

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• How can I utilize or mimic Application OnStart in an HttpModule?

  - by Sailing Judo

  We are trying to remove the global.asax from our many web applications in favor of HttpModules that are in a common code base. This works really well for many application events such as BeginRequest and PostAuthentication, but there is no Application Start event exposed in the HttpModule. I can think of a couple of smelly ways to overcome this deficit. For example, I can probably do this: protected virtual void BeginRequest(object sender, EventArgs e) { Log.Debug("Entered BeginRequest..."); var app = HttpContext.Current.Application; var hasBeenSet app["HasBeenExecuted"] == null ? false : true; if(!hasBeenSet) { app.Lock(); // ... do app level code app.Add("HasBeenSet", true); app.Unlock(); } // do regular begin request stuff ... } But this just doesn't smell well to me. What is the best way to invoke some application begin logic without having a global.asax?

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• directx audio video error message in debugmode

  - by clamp

  I have a c#/winforms application that uses directx to play some video and audio. whenever i start my application in debugmode i get this annoying message. i can click "continue" and everything seems to work fine. but i still want to get rid of this message. it does not show up in releasemode. Managed Debugging Assistant 'LoaderLock' has detected a problem in 'C:\pathtoexe.exe'. Additional Information: DLL 'C:\WINDOWS\assembly\GAC\Microsoft.DirectX.AudioVideoPlayback\1.0.2902.0__31bf3856ad364e35\Microsoft.DirectX.AudioVideoPlayback.dll' is attempting managed execution inside OS Loader lock. Do not attempt to run managed code inside a DllMain or image initialization function since doing so can cause the application to hang.

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• Reporting Services "cannot connect to the report server database"

  - by Dano

  We have Reporting Services running, and twice in the past 6 months it has been down for 1-3 days, and suddenly it will start working again. The errors range from not being able to view the tree root in a browser, down to being able to insert parameters on a report, but crashing before the report can generate. Looking at the logs, there is 1 error and 1 warning which seem to correspond somewhat. ERROR:Event Type: Error Event Source: Report Server (SQL2K5) Event Category: Management Event ID: 107 Date: 2/13/2009 Time: 11:17:19 AM User: N/A Computer: ******** Description: Report Server (SQL2K5) cannot connect to the report server database. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. WARNING: always comes before the previous error Event code: 3005 Event message: An unhandled exception has occurred. Event time: 2/13/2009 11:06:48 AM Event time (UTC): 2/13/2009 5:06:48 PM Event ID: 2efdff9e05b14f4fb8dda5ebf16d6772 Event sequence: 550 Event occurrence: 5 Event detail code: 0 Process information: Process ID: 5368 Process name: w3wp.exe Account name: NT AUTHORITY\NETWORK SERVICE Exception information: Exception type: ReportServerException Exception message: For more information about this error navigate to the report server on the local server machine, or enable remote errors. During the downtime we tried restarting everything from the server RS runs on, to the database it calls to fill reports with no success. When I came in monday morning it was working again. Anyone out there have any ideas on what could be causing these issues? Edit Tried both suggestions below several months ago to no avail. This issue hasn't arisen since, maybe something out of my control has changed....

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• Prevent Carousel scroll within scrollable Container (Sencha 2)?

  - by TragedyStruck

  I've got a Container with a header, content (Carousel) and a footer. The Container itself is therefor scrollable (vertical) to be able to scroll down to the footer. The Carousel can be swiped horizontally to change active item. I want to lock it to do only two thing: If starting to move vertically, only scroll Container If starting to move horizontally, only scroll Carousel If you now grab the Carousel you are able to scroll both ways at the same time. Example code: Ext.define('MyApp.view.MyContainer', { extend: 'Ext.Container', config: { scrollable: true, items: [ { xtype: 'container', items: [ { xtype: 'label', html: 'abc' } ] }, { xtype: 'carousel', height: 200, scrollable: false, items: [ { xtype: 'label', html: 'x' }, { xtype: 'label', html: 'y<br/>y<br/>y<br/>y<br/>y<br/>y<br/>y<br/>y' } ] }, { xtype: 'container', items: [ { xtype: 'label', html: 'def' } ] } ] } }); Using Sencha Touch 2.

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• Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

  - by Neil Barnwell

  So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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• Rails database relationships

  - by Danny McClelland

  Hi Everyone, I have three models that I want to interact with each other. Kase, Person and and Company. I have (I think) setup the relationships correctly: class Kase < ActiveRecord::Base #HAS ONE COMPANY has_one :company #HAS MANY PERSONS has_many :persons class Person < ActiveRecord::Base belongs_to :company class Company < ActiveRecord::Base has_many :persons def to_s; companyname; end I have put the select field on the create new Kase view, and the create new Person view as follows: <li>Company<span><%= f.select :company_id, Company.all %> </span></li> All of the above successfully shows a drop down menu dynamically populated with the company names within Companies. What I am trying to do is display the contact of the Company record within the kase and person show.html.erb. For example, If I have a company called "Acme, Inc." and create a new Kase called "Random Case" and choose within the create new case page "Acme, Inc." from the companies drop down menu. I would then want to display "Acme, Inc" along with "Acme, Inc. Mobile" etc. on the "Random Case" show.html.erb. I hope this makes sense to somebody! Thanks, Danny

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• animation on image view on grid view

  - by yahska

  i am having a grid view with 2 coloums and each item in grid view having one image and 2 textview below the image. i have added one button over each image and after clicking on button i want that image should scale and move down to bottom tab. like it should appear image drop down from its position in side one button of tabview. i am able to add animation on image using this code AnimationSet set = new AnimationSet(true); Animation trAnimation = new TranslateAnimation(0, 160,0, 100); trAnimation.setDuration(500); set.addAnimation(trAnimation); Animation scaleAnimation = AnimationUtils.loadAnimation(this, R.anim.anim_scale); set.addAnimation(scaleAnimation); set.setFillEnabled(true) ; set.setFillAfter(true); view.setAlpha(100) ; view.startAnimation(set); but problem is that image is not coming to bottom of screen it is going inside of grid item where it is placed . anybody knows how to move this image to bottom.

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• Is there a better way to serially submit multiple AJAX requests?

  - by friedo

  I have a page with multiple forms that I submit via Ajax POSTs serially. At first, I tried using synchronous XHR requests, but this causes the browser to lock up for the duration of the request, and breaks my DOM-manipulation effects, which is unacceptable. So the pattern I ended up using is basically this: var fcount = 0; // incremented for each form to be submitted function submit_form( num ) { var fdata = { ... }; // data from form # num $.ajax( { async: true, url: '/index.cgi', data: fdata, type: 'POST', success: function() { if ( num < fcount ) { submit_form( ++num ); } } } ); } $( '#submit_form_btn' ).click( function() { submit_form( 1 ) } ); The recursion strikes me as a bit of an ugly solution to what is essentially an iterative problem. Is there a cleaner or more elegant way that this could be handled?

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• Updating a listitem in an ASPX page in SharePoint Designer

  - by Andy

  Hey All, Right now I'm using SharePoint Designer to create a new aspx page. I am using a data view to display information from a list. One of the fields in the list is a choice field. I was wondering if there was anyway that I could display all of the other fields but allow one field in the list to be edited on the page without adding an edit link. Ideally, I would like a user to go in and be able to edit a field value (hopefully in a drop down list) within a data view without being redirected to the list or a form. I'm thinking there is a way to do this through javascript to embed inside the HTML or through a workflow of some sort. I'm new to javascript and don't know how to do this. I have tried to insert a drop down list and provide a data source for it but it will only show all of the field values in the list. Thus, I am unable to display the choice options, show the current value in the listitem and edit/update the listitem. Hopefully this makes sense. Can anyone help me out here? Thanks a lot, Andy

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• How to get coordinates when iPhone is locked/sleeping?

  - by lionfly

  For normal situations, the didUpdateToLocation (of CLLocationManager) does not work any more when the lock/sleep button is pushed, and your app cannot get further newLocation coordinates during the locked period. However, some apps CAN track during the locked period, and they will show the correct route when you unlocked and see the Mapview. Obviously there are ways to get the coordinates during the locked period. How to get the coordinates when the iPhone is locked/sleeping? Who has hints and further info, please post. Thanks.

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• Debugging in visual studio 2008 freezes entire system

  - by mat690

  Any time i try to debug in visual studio 2008 my entire system will freeze whenever a breakpoint is hit. I can move the mouse around and that remains responsive but nothing i click on does anything, I can bring up the task manager but can't do anything with it and i am able to lock/unlock the machine. I tried a fix that i found via google that suggested i disable advanced text services but it didn't work. I am using visual studio 2008 with SP1 running on Windows XP Pro, asking here is my last hope before formating/reinstalling so i hope someone can help me out. I debug by running the application in debug mode, the freeze happens no matter what the project size and it seems as if it is just the entire GUI that freezes, the computer carries on working just fine i just can't do anything with it because the GUI is totaly unresponsive.

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• detect shutdown in window service

  - by deepu

  hi, i have a windows service that get user details and save the result into log text file. and, my problem is when i shut down or log off my system, i also would like to save the time that i down my system into that log file. but, i don't know how to do that. I checked the winproc method to detect shutdown operation but i was not able to use it on window service, on googling found it can be used with forms only. how can we detect user have clicked shutdown or log off and do some action. so,please give me some idea or suggestion on that. i have used it for logoff but on log entry is made when i logoff the system protected override void OnSessionChange(SessionChangeDescription changeDescription) { this.RequestAdditionalTime(250000); //gives a 25 second delay on Logoff if (changeDescription.Reason == SessionChangeReason.SessionLogoff) { // Add your save code here StreamWriter str = new StreamWriter("D:\\Log.txt", true); str.WriteLine("Service stoped due to " + changeDescription.Reason.ToString() + "on" + DateTime.Now.ToString()); str.Close(); } base.OnSessionChange(changeDescription); }

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• SortList duplicated key, but it shouldn't

  - by Luca

  I have a class which implements IList interface. I requires a "sorted view" of this list, but without modifying it (I cannot sort directly the IList class). These view shall be updated when the original list is modified, keeping items sorted. So, I've introduced a SortList creation method which create a SortList which has a comparer for the specific object contained in the original list. Here is the snippet of code: public class MyList<T> : ICollection, IList<T> { ... public SortedList CreateSortView(string property) { try { Lock(); SortListView sortView; if (mSortListViews.ContainsKey(property) == false) { // Create sorted view sortView = new SortListView(property, Count); mSortListViews.Add(property, sortView); foreach (T item in Items) sortView.Add(item); } else sortView = mSortListViews[property]; sortView.ReferenceCount++; return (sortView); } finally { Unlock(); } } public void DeleteSortView(string property) { try { Lock(); // Unreference sorted view mSortListViews[property].ReferenceCount--; // Remove sorted view if (mSortListViews[property].ReferenceCount == 0) mSortListViews.Remove(property); } finally { Unlock(); } } protected class SortListView : SortedList { /// <summary> /// /// </summary> /// <param name="property"></param> /// <param name="capacity"></param> public SortListView(string property, int capacity) : base(new GenericPropertyComparer(typeof(T).GetProperty(property, BindingFlags.Instance | BindingFlags.Public)), capacity) { } /// <summary> /// Reference count. /// </summary> public int ReferenceCount = 0; /// <summary> /// /// </summary> /// <param name="item"></param> public void Add(T item) { Add(item, item); } /// <summary> /// /// </summary> /// <param name="item"></param> public void Remove(T item) { // Base implementation base.Remove(item); } /// <summary> /// Compare object on a generic property. /// </summary> class GenericPropertyComparer : IComparer { #region Constructors /// <summary> /// Construct a GenericPropertyComparer specifying the property to compare. /// </summary> /// <param name="property"> /// A <see cref="PropertyInfo"/> which specify the property to be compared. /// </param> /// <remarks> /// The <paramref name="property"/> parameter imply that the compared objects have the specified property. The property /// must be readable, and its type must implement the IComparable interface. /// </remarks> public GenericPropertyComparer(PropertyInfo property) { if (property == null) throw new ArgumentException("property doesn't specify a valid property"); if (property.CanRead == false) throw new ArgumentException("property specify a write-only property"); if (property.PropertyType.GetInterface("IComparable") == null) throw new ArgumentException("property type doesn't IComparable"); mSortingProperty = property; } #endregion #region IComparer Implementation public int Compare(object x, object y) { IComparable propX = (IComparable)mSortingProperty.GetValue(x, null); IComparable propY = (IComparable)mSortingProperty.GetValue(y, null); return (propX.CompareTo(propY)); } /// <summary> /// Sorting property. /// </summary> private PropertyInfo mSortingProperty = null; #endregion } } /// <summary> /// Sorted views of this ReactList. /// </summary> private Dictionary<string, SortListView> mSortListViews = new Dictionary<string, SortListView>(); } Practically, class users request to create a SortListView specifying the name of property which determine the sorting, and using the reflection each SortListView defined a IComparer which keep sorted the items. Whenever an item is added or removed from the original list, every created SortListView will be updated with the same operation. This seems good at first chance, but it creates me problems since it give me the following exception when adding items to the SortList: System.ArgumentException: Item has already been added. Key in dictionary: 'PowerShell_ISE [C:\Windows\sysWOW64\WindowsPowerShell\v1.0\PowerShell_ISE.exe]' Key being added: 'PowerShell_ISE [C:\Windows\system32\WindowsPowerShell\v1.0\PowerShell_ISE.exe]' As you can see from the exception message, thrown by SortedListView.Add(object), the string representation of the key (the list item object) is different (note the path of the executable). Why SortList give me that exception? To solve this I tried to implement a GetHashCode implementation for the underlying object, but without success: public override int GetHashCode() { return ( base.GetHashCode() ^ mApplicationName.GetHashCode() ^ mApplicationPath.GetHashCode() ^ mCommandLine.GetHashCode() ^ mWorkingDirectory.GetHashCode() ); }

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• Google App Engine - Dealing with concurrency issues of storing an object

  - by Spines

  My User object that I want to create and store in the datastore has an email, and a username. How do I make sure when creating my User object that another User object doesn't also have either the same email or the same username? If I just do a query to see if any other users have already used the username or the email, then there could be a race condition. UPDATE: The solution I'm currently considering is to use the MemCache to implement a locking mechanism. I would acquire 2 locks before trying to store the User object in the datastore. First a lock that locks based on email, then another that locks based on username. Since creating new User objects only happens at user registration time, and it's even rarer that two people try to use either the same username or the same email, I think it's okay to take the performance hit of locking. I'm thinking of using the MemCache locking code that is here: http://appengine-cookbook.appspot.com/recipe/mutex-using-memcache-api/ What do you guys think?

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