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  • Binding Entity Framework Collections Simply Using ASP.NET MVC

    - by jpcmorton
    To begin with: Using Entity Framework v4.0. ASP.NET MVC 2.0. Visual Studio 2010. I have a model that consists simply of an order & order items. What I want to do is simply bind that model without too much hassle where possible (avoiding type converters, etc). Simply the model looks like this: public class Order { public int ID { get; set; } public string OrderNumber { get; set; } public EntityCollection<OrderItem> Items { get; set; } } public class OrderItem { public int ID { get; set; } public string Qty { get; set; } } This is as simple as I want to keep it. This model is coming directly from the code generated by the entity framework generator. I would prefer to use the model directly from the entity framework (I know there are views saying this is a bad thing, but alas). I then have the View looking like this: <% using (Html.BeginForm()) {%> <%: Html.ValidationSummary(true) %> <fieldset> <legend>Fields</legend> <div class="editor-label"> <%: Html.LabelFor(model => model.ID) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.ID) %> <%: Html.ValidationMessageFor(model => model.ID) %> </div> <div class="editor-label"> <%: Html.LabelFor(model => model.OrderNumber) %> </div> <div class="editor-field"> <%: Html.TextBoxFor(model => model.OrderNumber)%> <%: Html.ValidationMessageFor(model => model.OrderNumber)%> </div> <div id="lineItems"> Where I need to put my line items to be edited, inserted </div> <p> <input type="submit" value="Create" /> </p> </fieldset> <% } %> What I want to do is have a situation where I can use dynamic line items (using javascript). Problems are this: How to go about inserting the initial line item (within the lineItems div). This need to be strongly typed and use the built in validation framework of MVC. Best way to go about inserting line items dynamically so that on the postback there is a complete bind to the model without too much messing around (id = 1,2,3,4, etc). Any help, examples, tips, etc would be appreciated.

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  • Preventing concurrent data modification in Web based app

    - by Manoj
    Hi, I am building a web app in Silverlight which allows users to view and edit a database. In order to prevent multiple users from editing the same data, I was thinking of implementing a lock and key mechanism, so that other users are made to wait when one particular user is editing the data. Is there any way in which we can have variable(flag specifying if a user is editing data) in the server which can be shared across multiple clients? Is there a better way to manage this type of conurrent data access issues?

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  • Oracle (PL/SQL): Is UPDATE RETURNING concurrent?

    - by Jaap
    I'm using table with a counter to ensure unique id's on a child element. I know it is usually better to use a sequence, but I can't use it because I have a lot of counters (a customer can create a couple of buckets and each of them needs to have their own counter, they have to start with 1 (it's a requirement, my customer needs "human readable" keys). I'm creating records (let's call them items) that have a prikey (bucket_id, num = counter). I need to guarantee that the bucket_id / num combination is unique (so using a sequence as prikey won't fix my problem). The creation of rows doesn't happen in pl/sql, so I need to claim the number (btw: it's not against the requirements to have gaps). My solution was: UPDATE bucket SET counter = counter + 1 WHERE id = param_id RETURNING counter INTO num_forprikey; PL/SQL returns var_num_forprikey so the item record can be created. Question: Will I always get unique num_forprikey even if the user concurrently asks for new items in a bucket?

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  • How to implement a category hierarchy using collections

    - by Luke101
    Hello, I have about 200 categories that are nested. I am currently reading the documention on the C5 generics library. I am not sure if the C5 library is overkill or not. I am looking at converting all my custom algorithms to the C5 implemention. This is what I need. If a certain category is chosen i need to find its parents, siblings, direct children, and all children. This is the way I have it set up. To find the: Parents: I start from the current location then loop through the list and find the current parent. When I find the parent I loop through the whole list again to find the next parent and so on. Siblings: I loop through the whole list and find all the nodes that have the same parent as the choosen node. direct children: I loop through the whole list and find all nodes that is a parent of the choosen node. All Children: This one took me a while to figure out. But I used recursion to find all children of the choosen node. Is there a better way to implement something like this?

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  • Inconsistency in java.util.concurrent.Future?

    - by loganj
    For the sake of argument, let's say I'm implementing Future for a task which is not cancelable. The Java 6 API doc says: After [cancel()] returns, subsequent calls to isDone() will always return true. [cancel()] returns false if the task could not be cancelled, typically because it has already completed normally It also says: [isDone()] returns true if this task completed. But what if my cancellation fails not because the task is already completed, but because it simply cannot be cancelled? Is there a way out of this contradiction (other than making my uncancelable task cancelable and sidestepping it altogether)?

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  • High concurrent request server in ruby

    - by WedTM
    I'm trying to write a simple server that will grab an mp3 file from rackspace cloudfiles, and stream it to a client over HTTP. The server must be able to stream to multiple clients simultaneously, however, I'm finding it difficult to come up with a viable solution. Anyone have some ideas?

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  • How to iterate JPA collections in Google App engine

    - by palto
    Hi I use Google App Engine with datanucleus and JPA. I'm having a real hard time grasping how I'm supposed to read stuff from data store and pass it to JSP. If I load a list of POJOs with entitymanager and pass it to JSP, it crashes to org.datanucleus.exceptions.NucleusUserException: Object Manager has been closed. I understand why this is happening. Obviously because I fetch the list, close the entity manager and pass it to JSP, at which point it will fail because the list is lazy. How do I make the list NOT lazy without resorting to hacks like calling size() or something like that? Here is what I'm trying to do: @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setAttribute("parties", getParties()); RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/WEB-INF/parties.jsp"); dispatcher.forward(req, resp); } private List<Party> getParties(){ EntityManager em = entityManagerProvider.get(); try{ Query query = em.createQuery("SELECT p FROM Party p"); return query.getResultList(); }finally{ em.close(); } }

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  • Fluent / NHibernate Collections of the same class

    - by Charlie Brown
    I am new to NHibernate and I am having trouble mapping the following relationships within this class. public class Category : IAuditable { public virtual int Id { get; set; } public virtual string Name{ get; set; } public virtual Category ParentCategory { get; set; } public virtual IList<Category> SubCategories { get; set; } public Category() { this.Name = string.Empty; this.SubCategories = new List<Category>(); } } Class Maps (although, these are practically guesses) public class CategoryMap : ClassMap<Category> { public CategoryMap() { Id(x => x.Id); Map(x => x.Name); References(x => x.ParentCategory) .Nullable() .Not.LazyLoad(); HasMany(x => x.SubCategories) .Cascade.All(); } } Each Category may have a parent category, some Categories have many subCategories, etc, etc I can get the Category to Save correctly (correct subcategories and parent category fk exist in the database) but when loading, it returns itself as the parent category. I am using Fluent for the class mapping, but if someone could point me in the right direction for just plain NHibernate that would work as well.

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  • Exporting collections

    - by Ruslan
    Hi, have select like select trn_dt,collect(ac_no) from transactions where rownum < 1000 group by trn_dt i'm doing it in SQL Navigator. But i can't export results! Table collect(ac_no) is not exported. Is there any way out?

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  • Binding Listbox item source to a collection of collections in windows phone 7

    - by Tee
    Hi there, I am trying to bind a Listbox ItemSource to a collection of multiple Lists. i.e. List PersonCollection List Person List Collection Now I need to show items from both of these list. In wpf you could use HierarchicalDataTemplate i believe, but not sure how I can do it in windows phone 7. Tried with Blend and it generates the following data template. <DataTemplate x:Key="PersonDataTemplate"> <Grid> <StackPanel Margin="0,0,1,0" Orientation="Vertical" VerticalAlignment="Top"> <TextBlock Margin="0,0,1,0" TextWrapping="Wrap" Text="{Binding Person[0].Name}" d:LayoutOverrides="Width"/> <TextBlock Margin="0,0,1,0" TextWrapping="Wrap" Text="{Binding Collection[0].Total}" d:LayoutOverrides="Width"/> </StackPanel> </Grid> </DataTemplate> Is there another way I can do this? I have tried to set the DataContext of Textbox in DataTemplate to individual arrays but did not seem to work. Cant find anything similar on the net apart from the confirmation that HierarchicalDataTemplate is not supported in Windows Phone 7. I have other ways to do but none elegant.. Thanks in advance. Regards

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  • Java: Making concurrent MySQL queries from multiple clients synchronised

    - by Misha Gale
    I work at a gaming cybercafe, and we've got a system here (smartlaunch) which keeps track of game licenses. I've written a program which interfaces with this system (actually, with it's backend MySQL database). The program is meant to be run on a client PC and (1) query the database to select an unused license from the pool available, then (2) mark this license as in use by the client PC. The problem is, I've got a concurrency bug. The program is meant to be launched simultaneously on multiple machines, and when this happens, some machines often try and acquire the same license. I think that this is because steps (1) and (2) are not synchronised, i.e. one program determines that license #5 is available and selects it, but before it can mark #5 as in use another copy of the program on another PC tries to grab that same license. I've tried to solve this problem by using transactions and table locking, but it doesn't seem to make any difference - Am I doing this right? Here follows the code in question: public LicenseKey Acquire() throws SmartLaunchException, SQLException { Connection conn = SmartLaunchDB.getConnection(); int PCID = SmartLaunchDB.getCurrentPCID(); conn.createStatement().execute("LOCK TABLE `licensekeys` WRITE"); String sql = "SELECT * FROM `licensekeys` WHERE `InUseByPC` = 0 AND LicenseSetupID = ? ORDER BY `ID` DESC LIMIT 1"; PreparedStatement statement = conn.prepareStatement(sql); statement.setInt(1, this.id); ResultSet results = statement.executeQuery(); if (results.next()) { int licenseID = results.getInt("ID"); sql = "UPDATE `licensekeys` SET `InUseByPC` = ? WHERE `ID` = ?"; statement = conn.prepareStatement(sql); statement.setInt(1, PCID); statement.setInt(2, licenseID); statement.executeUpdate(); statement.close(); conn.commit(); conn.createStatement().execute("UNLOCK TABLES"); return new LicenseKey(results.getInt("ID"), this, results.getString("LicenseKey"), results.getInt("LicenseKeyType")); } else { throw new SmartLaunchException("All licenses of type " + this.name + "are in use"); } }

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  • Is there a concurrent container library for C++

    - by Lirik
    I'm looking for implementations of lock-free containers: Blocking Queue Blocking Stack Hash Map etc... Are there any good libraries out there? I would like to refrain from writing these data structures... I would much rather use something that has been tested by the community.

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  • Tuning garbage collections for low latency

    - by elec
    I'm looking for arguments as to how best to size the young generation (with respect to the old generation) in an environment where low latency is critical. My own testing tends to show that latency is lowest when the young generation is fairly large (eg. -XX:NewRatio <3), however I cannot reconcile this with the intuition that the larger the young generation the more time it should take to garbage collect. The application runs on linux, jdk 6 before update 14, i.e G1 not available.

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  • NoSQL for concurrent reads/writes

    - by Mickael Marrache
    After getting some performance issues for an application using a MySQL database, I'm thinking of using NoSQL solutions. My architecture is as follows: One application receives messages from the network at a high throughput (i.e. 50000 messages/sec). Each message is stored in the DB, so it's important for the write rate to be as fast as the arrival rate. Then, I also have some PHP pages that accesses the DB to get the data stored by the other application. It's important for me that the retrieved data is as relevant as possible (i.e. not old data, let's say not more than 5 seconds old). Also, the data is not critical, so I don't need any security mechanism to avoid losing the data. I see there are a lot of NoSQL solutions, but I don't know if they are all relevant. Could you please provide me some directions. Thanks

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  • My Rails session is getting reset when I have concurrent requests

    - by alex_c
    I think I might be misunderstanding something about Rails sessions, so please bear with me, I might not be phrasing my question the best way. I'm working on an iPhone app with a Ruby on Rails backend. I have a web view which by default goes to the index action of one controller (and uses sessions), and in the background a bunch of API calls going to a different controller (and which don't need to use sessions). The problem is, the sessions set by my web view seem to be overwitten by the API calls. My staging server is pretty slow, so there's lots of time for the requests to overlap each other - what I see in the logs is basically this: Request A (first controller) starts. Session is empty. Request B (second controller) starts. Session is empty. Request A finishes. Request A has done authentication, and stored the user ID in the session. Session contains user ID. Request B finishes. Session is empty. Request C starts. Session is empty - not what I want. Now, the strange thing is that request B should NOT be writing anything to the session. I do have before and after filters which READ from the session - things like: user = User.find_by_id(session[:id]) or logger.debug session.inspect and if I remove all of those, then everything works as expected - session contents get set by request A, and they're still there when request C starts. So. I think I'm missing something about how sessions work. Why would reading from the session overwrite it? Should I be accessing it some other way? Am I completely on the wrong track and the problem is elsewhere? Thank you for any insights!

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  • Java Download Concurrent Data

    - by xger86x
    Hi, i'm developing an app which download map tiles around different places in a city. To do this, i have one thread for each place in which i select the tiles and create a thread to download each. Well, the question is how to avoid creating a thread for a tile that already exists in the thread pool. Should not just check if the file exists, since it is possible that the thread for that tile already exists (other place already need that tile) but the file has not been created- Any idea? Thanks

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  • Neat way of gettings position of my Object in linq collections

    - by Steve
    I currently have a object called Week. A week is part of a Season object. the season can contain many weeks. What I want to do is find the position of my week (is it the first week in the season (so #1) or is it the second (so #2). int i = 0; foreach ( var w in Season.Weeks.OrderBy(w => w.WeekStarts)){ if(w.Id == Id){ return i; } i+=1; } At the moment this is what I have. I order the weeks in a second by there start date to make sure they are in the correct order. and I cycle through them until I find the week that matches the week I am currently looking at. and return the int that I have been counting up.. I feel there should be a easier linq way to do this as it feels pretty messy!

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  • Type casting Collections using Conversion Operators

    - by Vyas Bharghava
    The below code gives me User-defined conversion must convert to or from enclosing type, while snippet #2 doesn't... It seems that a user-defined conversion routine must convert to or from the class that contains the routine. What are my alternatives? Explicit operator as extension method? Anything else? public static explicit operator ObservableCollection<ViewModel>(ObservableCollection<Model> modelCollection) { var viewModelCollection = new ObservableCollection<ViewModel>(); foreach (var model in modelCollection) { viewModelCollection.Add(new ViewModel() { Model = model }); } return viewModelCollection; } Snippet #2 public static explicit operator ViewModel(Model model) { return new ViewModel() {Model = model}; } Thanks in advance!

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  • group object with equal collections

    - by Jeroen
    Hi, Suppose 2 classes, Person and Pet. Each person has a collection of 1 or more pets. How do i group the Person in to a collection where they share the same pets. Example: Person 1: Cat, Dog, Spider Person 2: Cat, Spider, Snake Person 3: Dog Person 4: Spider, Cat, Dog Person 5: Dog What i want as a result is this: Group 1: Person 1, Person 4 Group 2: Person 3, Person 5 Group 3: Person 2 How do i achieve this using LINQ?

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  • server controls complex properties with sub collections.

    - by Richard Friend
    Okay i have a custom server control that has some autocomplete settings, i have this as follows and it works fine. /// <summary> /// Auto complete settings /// </summary> [System.ComponentModel.DesignerSerializationVisibility (System.ComponentModel.DesignerSerializationVisibility.Content), PersistenceMode(PersistenceMode.InnerProperty), Category("Data"), Description("Auto complete settings"), NotifyParentProperty(true)] public AutoCompleteLookupSettings AutoComplete { private set; get; } I also have a ParameterCollection that is really related to the auto complete settings, currently this collection resides off the control itself like so : /// <summary> /// Parameters for any data lookups /// </summary> [System.ComponentModel.DesignerSerializationVisibility(System.ComponentModel.DesignerSerializationVisibility.Content), PersistenceMode(PersistenceMode.InnerProperty)] public ParameterCollection Parameters { get; set; } What i would like to do is move the parameter collection inside of the AutoCompleteSettings as it really relates to my autocomplete, i have tried this but to no avail.. I would like to move from <cc1:TextField ID="TextField1" runat='server'> <AutoComplete MethodName="GetTest" TextField="Item1" TypeName ="AppFrameWork.Utils" /> <Parameters> <asp:ControlParameter ControlID="txtTest" PropertyName="Text" Name="test" /> </Parameters> </cc1:TextField> To <cc1:TextField ID="TextField1" runat='server'> <AutoComplete MethodName="GetTest" TextField="Item1" TypeName ="AppFrameWork.Utils" > <Parameters> <asp:ControlParameter ControlID="txtTest" PropertyName="Text" Name="test" /> </Parameters> </AutoComplete> </cc1:TextField>

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  • Databinding to the DataGridView (Enums + Collections)

    - by Ian
    I'm after a little help with the techniques to use for Databinding. It's been quite a while since I used any proper data binding and want to try and do something with the DataGridView. I'm trying to configure as much as possible so that I can simply designed the DatagridView through the form editor, and then use a custom class that exposes all my information. The sort of information I've got is as follows: public class Result { public String Name { get; set; } public Boolean PK { get; set; } public MyEnum EnumValue { get; set; } public IList<ResultInfos> { get; set; } } public class ResultInfos { get; set; } { public class Name { get; set; } public Int Value { get; set; } public override String ToString() { return Name + " : " Value.ToString(); } } I can bind to the simple information without any problem. I want to bind to the EnumValue with a DataGridViewComboBoxColumn, but when I set the DataPropertyName I get exceptions saying the enum values aren't valid. Then comes the ResultInfo collection. Currently I can't figure out how to bind to this and display my items, again really I want this to be a combobox, where the 1st Item is selected. Anyone any suggestions on what I'm doing wrong? Thanks

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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • Binding collections to DataGridView in Windows Forms

    - by Sergey
    I'm trying to bing collection to DataGridView. As it turns out it's impossible for user to edit anything in this DataGridView although EditMode is set to EditOnKeystrokeOrF2. Here is the simplified code: public Supplies() { InitializeComponent(); List<string> l = new <string>(); l.Add("hello"); this.SuppliesDataGridView.DataSource = l; } It also doesn't work when I change collection type to SortableBindingList, Dictionary or even use BindingSource. What can be wrong here?

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