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• Bind button visibility to the expresion (C#)

  - by drasto

  I have a delete button in each row of GridView (component ASP.NET). I want some of the delete buttons to be invisible. The visibility of the delete button should depend on the data that are back the row. GridView is backed by EntityDataSource. GridView displays entities called Category, one instance in each row. Entity Category has (besides others) also a field of type EntityCollection. Name of that field is Items. Basically I want to allow user to delete a row only if the Items field of backing Category entity is an empty collection. I cannot make up the binding of Visible property. I have no experience with bindings and Google does not really help. This is how the button looks right now: <asp:Button ID="DeleteButton" runat="server" CommandName="Delete" Text="Delete" Visible=??? ></asp:Button> I don't know what should replace ???. The button schold be visible only when this expression evaluates to true: ((SimpleEShop.Model.Category) dataItem).Items.LongCount() <= 0 where dataItem variable contains data of current row in the table. What is the binding that I need ?

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• Associating Models with Polymorphic

  - by Josh Crowder

  I am trying to associate Contacts with Classes but as two different types. Current_classes and Interested_classes. I know I need to enable polymorphic but I am not sure as to where it needs to be enabled. This is what I have at the moment class CreateClasses < ActiveRecord::Migration def self.up create_table :classes do |t| t.string :class_type t.string :class_name t.string :date t.timestamps end end def self.down drop_table :classes end end class CreateContactsInterestedClassesJoin < ActiveRecord::Migration def self.up create_table 'contacts_interested_classes', :id => false do |t| t.column 'class_id', :integer t.column 'contact_id', :integer end end def self.down drop_table 'contacts_interested_classes' end end class CreateContactsCurrentClassesJoin < ActiveRecord::Migration def self.up create_table 'contacts_current_classes', :id => false do |t| t.column 'class_id', :integer t.column 'contact_id', :integer end end def self.down drop_table 'contacts_current_classes' end end And then inside of my Contacts Model I want to have something like this. class Contact < ActiveRecord::Base has_and_belongs_to_many :classes, :join_table => "contacts_interested_classes", :foreign_key => "class_id" :as => 'interested_classes' has_and_belongs_to_many :classes, :join_table => "contacts_current_classes", :foreign_key => "class_id" :as => 'current_classes' end What am I doing wrong?

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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• Declaring a string array in class header file - compiler thinks string is variable name?

  - by Dave

  Hey everybody, I need a bit of a hand with declaring a string array in my class header file in C++. atm it looks like this: //Maze.h #include <string> class Maze { GLfloat mazeSize, mazeX, mazeY, mazeZ; string* mazeLayout; public: Maze ( ); void render(); }; and the constructor looks like this: //Maze.cpp #include <GL/gl.h> #include "Maze.h" #include <iostream> #include <fstream> Maze::Maze( ) { cin >> mazeSize; mazeLayout = new string[mazeSize]; mazeX = 2/mazeSize; mazeY = 0.25; mazeZ = 2/mazeSize; } I'm getting a compiler error that says: In file included from model-view.cpp:11: Maze.h:14: error: ISO C++ forbids declaration of ‘string’ with no type Maze.h:14: error: expected ‘;’ before ‘*’ token and the only sense that makes to me is that for some reason it thinks I want string as a variable name not as a type declaration. If anybody could help me out that would be fantastic, been looking this up for a while and its giving me the shits lol. Cheers guys

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• How do I create a selection list in ASP.NET MVC?

  - by Gary McGill

  I have a database table that records what publications a user is allowed to access. The table is very simple - it simply stores user ID/publication ID pairs: CREATE TABLE UserPublication (UserId INTEGER, PublicationID INTEGER) The presence of a record for a given user & publication means that the user has access; absence of a record implies no access. I want to present my admin users with a simple screen that allows them to configure which publications a user can access. I would like to show one checkbox for each of the possible publications, and check the ones that the user can currently access. The admin user can then check or un-check any number of publications and submit the form. There are various publication types, and I want to group the similarly-typed publications together - so I do need control over how the publications are presented (I don't want to just have a flat list). My view model obviously needs to have a list of all the publications (since I need to display them all regardless of the current selection), and I also need a list of the publications that the user currently has access to. (I'm not sure whether I'd be better off with a single list where each item includes the publication ID and a yes/no field?). But that's as far as I've got. I've really no idea how to go about binding this to some checkboxes. Where do I start?

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• Docs for auto-generated methods in Ruby on Rails

  - by macek

  Rails has all sorts of auto-generated methods that I've often times struggled to find documentation for. For example, in routes.rb, if I have: map.resources :projects do |p| p.resources :tasks end This will get a plethora of auto-generate path and url helpers. Where can I find documentation for how to work with these paths? I generally understand how to work with them, but more explicit docs might help me understand some of the magic that happens behind the scenes. # compare project_path(@project) project_task_path(@project, @task) # to project_path(:id => @project.id) project_task_path(:project_id => @project.id, :id => @task.id) Also, when I change an attribute on a model, @post.foo_changed? will be true. Where can I find documentation for this and all other magical methods that are created like this? If the magic is there, I'd love to take advantage of it. And finally: Is there a complete resource for config.___ statements for environment.rb? I was able to find docs for Configuration#gem but what attributes can I set within the stubs like config.active_record.___, config.action_mailer.___, config.action_controller.___, etc. Again, I'm looking for a complete resource here, not just a settings for the examples I provided. Even if you can only answer one of these questions, please chime in. These things seem to have been hiding from me and it's my goal to get them some more exposure, so I'll be upvoting all links to docs that point me to what I'm looking for. Thanks! ps, If they're not called auto-generated methods, I apologize. Someone can teach me a lesson here, too :) Edit I'm not looking for tutorials here, folks. I have a fair amount of experience with rails; I'm just looking for complete docs. E.g., I understand how routing works, I just want docs where I can read about all of the usage options.

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• BeginInvoke on ObservableCollection not immediate.

  - by Padu Merloti

  In my code I subscribe to an event that happens on a different thread. Every time this event happens, I receive an string that is posted to the observable collection: Dispatcher currentDispatcher = Dispatcher.CurrentDispatcher; var SerialLog = new ObservableCollection<string>(); private void hitStation_RawCommandSent(object sender, StringEventArgs e) { string command = e.Value.Replace("\r\n", ""); Action dispatchAction = () => SerialLog.Add(command); currentDispatcher.BeginInvoke(dispatchAction, DispatcherPriority.Render); } The code below is in my view model (could be in the code behind, it doesn't matter in this case). When I call "hitstation.PrepareHit", the event above gets called a couple times, then I wait and call "hitStation.HitBall", and the event above gets called a couple more times. private void HitBall() { try { try { Mouse.OverrideCursor = Cursors.Wait; //prepare hit hitStation.PrepareHit(hitSpeed); Thread.Wait(1000); PlayWarning(); //hit hitStation.HitBall(hitSpeed); } catch (TimeoutException ex) { MessageBox.Show("Timeout hitting ball: " + ex.Message); } } finally { Mouse.OverrideCursor = null; } } The problem I'm having is that the ListBox that is bound to my SerialLog gets updated only when the HitBall method finishes. I was expecting seeing a bunch of updates from the PrepareHit, a pause and then a bunch more updates from the HitBall. I've tried a couple of DispatcherPriority arguments, but they don't seem to have any effect.

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• Saving owned/child objects in Hibernate

  - by maxdj

  I'm having a hard time wrapping my head around the way hibernate objects work. Here's a little chunk of what my model looks like: JobOpening: @ManyToMany(fetch=FetchType.EAGER,cascade=CascadeType.ALL) @JoinTable( name="jobOpening_questionSet", joinColumns=@JoinColumn(name="jobOpenings_id"), inverseJoinColumns=@JoinColumn(name="questionSets_id") ) @IndexColumn(name="question_sets_idx",base=0,nullable=false) public List<QuestionSet> getQuestionSets() { return questionSets; } QuestionSet: @ManyToMany(mappedBy="questionSets",fetch=FetchType.EAGER) public Set<JobOpening> getJobOpenings() { return jobOpenings; } @OneToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER) @IndexColumn(name="questions_idx",base=0) @JoinColumn(name="questionset_id",nullable=false) public List<FormQuestion> getQuestions() { return questions; } FormQuestion: @ManyToOne @JoinColumn(name="questionset_id", insertable=false, updatable=false, nullable=false) @OnDelete(action=OnDeleteAction.CASCADE) public QuestionSet getQuestionSet() { return questionSet; } Now how would I go about, say, modifying a question in the question set, or changing which jobs a questionset is associated with? For example, to edit a question in a questionset, I imagine I should be able to just get the question via its id, change some values, and merge() it back in, but this doesn't work. I'm using Hibernate from Spring (appfuse), usually as detached objects.

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• Call to a member function num_rows() on a non-object

  - by Patrick

  I need to get the number of rows of a query (so I can paginate results). As I'm learning codeigniter (and OO php) I wanted to try and chain a -num_rows() to the query, but it doesn't work: //this works: $data['count'] = count($this->events->findEvents($data['date'], $data['keyword'])); //the following doesn't work and generates // Fatal Error: Call to a member function num_rows() on a non-object $data['count2'] = $this->events->findEvents($data['date'], $data['keyword'])->num_rows(); the model returns an array of objects, and I think this is the reason why I can't use a method on it. function findEvents($date, $keyword, $limit = NULL, $offset = NULL) { $data = array(); $this->db->select('events.*, venues.*, events.venue AS venue_id'); $this->db->join('venues', 'events.venue = venues.id'); if ($date) { $this->db->where('date', $date); } if ($keyword) { $this->db->like('events.description', $keyword); $this->db->or_like('venues.description', $keyword); $this->db->or_like('band', $keyword); $this->db->or_like('venues.venue', $keyword); $this->db->or_like('genre', $keyword); } $this->db->order_by('date', 'DESC'); $this->db->order_by('events.priority', 'DESC'); $this->db->limit($limit, $offset); //for pagination purposes $Q = $this->db->get('events'); if ($Q->num_rows() > 0) { foreach ($Q->result() as $row) { $data[] = $row; } } $Q->free_result(); return $data; } Is there anything that i can do to be able to use it? EG, instead of $data[] = $row; I should use another (OO) syntax?

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• Understanding many to many relationships and Entity Framework

  - by Anders Svensson

  I'm trying to understand the Entity Framework, and I have a table "Users" and a table "Pages". These are related in a many-to-many relationship with a junction table "UserPages". First of all I'd like to know if I'm designing this relationship correctly using many-to-many: One user can visit multiple pages, and each page can be visited by multiple users..., so am I right in using many2many? Secondly, and more importantly, as I have understood m2m relationships, the User and Page tables should not repeat information. I.e. there should be only one record for each user and each page. But then in the entity framework, how am I able to add new visits to the same page for the same user? That is, I was thinking I could simply use the Count() method on the IEnumerable returned by a LINQ query to get the number of times a user has visited a certain page. But I see no way of doing that. In Linq to Sql I could access the junction table and add records there to reflect added visits to a certain page by a certain user, as many times as necessary. But in the EF I can't access the junction table. I can only go from User to a Pages collection and vice versa. I'm sure I'm misunderstanding relationships or something, but I just can't figure out how to model this. I could always have a Count column in the Page table, but as far as I have understood you're not supposed to design database tables like that, those values should be collected by queries... Please help me understand what I'm doing wrong...

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• Seed has_many relation using mass assignment

  - by rnd

  Here are my two models: class Article < ActiveRecord::Base attr_accessible :content has_many :comments end class Comment < ActiveRecord::Base attr_accessible :content belongs_to :article end And I'm trying to seed the database in seed.rb using this code: Article.create( [{ content: "Hi! This is my first article!", comments: [{content: "It sucks"}, {content: "Best article ever!"}] }], without_protection: true) However rake db:seed gives me the following error message: rake aborted! Comment(#28467560) expected, got Hash(#13868840) Tasks: TOP => db:seed (See full trace by running task with --trace) It is possible to seed the database like this? If yes a follow-up question: I've searched some and it seems that to do this kind of (nested?) mass assignment I need to add 'accepts_nested_attributes_for' for the attributes I want to assign. (Possibly something like 'accepts_nested_attributes_for :article' for the Comment model) Is there a way to allow this similar to the 'without_protection: true'? Because I only want to accept this kind of mass assignment when seeding the database.

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• MVC: Submit one form from a page with multiple forms

  - by Rob

  I'm working in an ASP.NET 3.5 MVC application where i've got a view with multiple forms in it. Form 1 contains information about products and will form a shoppingcart with a remove button. Form 2 is as below and is to be used to get the information from the shoppingcart and create an order of it. <% using (Html.BeginForm()) { %> <%=Html.Hidden(Order.ProductId", "E63EF586-F625-4C8D-B82E-E63A6FA4A63C")%> <%=Html.Hidden(Order.Amount", 1)%> <input type="submit" value="Pay" /> <%} % The first form contains a similar beginform with a foreach loop to get the information about the products from the model. When i use the submit button on the second form everything seems to be submitted and the action in the controller for the first form is trying to handle the request. That is where the error occurce because the information in the viewmodel isn't corresponding to what is being expected. The controller which is trying to handle the request: [AcceptVerbs(HttpVerbs.Post)] public ActionResult ShowShoppingcartForm([Bind(Prefix = "Order")] MyViewmodel viewModel) { //.. } The controller which is expected to handle the request: [AcceptVerbs(HttpVerbs.Post)] public ActionResult SaveOrder([Bind(Prefix = "Order")] MyViewmodel viewModel) { throw new NotImplementedException(); }

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• Rails: Getting rid of "X is invalid" validation errors

  - by DJTripleThreat

  I have a sign-up form that has nested associations/attributes whatever you want to call them. My Hierarchy is this: class User < ActiveRecord::Base acts_as_authentic belongs_to :user_role, :polymorphic => true end class Customer < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end class Employee < ActiveRecord::Base has_one :user, :as => :user_role, :dependent => :destroy accepts_nested_attributes_for :user, :allow_destroy => true validates_associated :user end I have some validation stuff in these classes as well. My problem is that if I try to create and Customer (or Employee etc) with a blank form I get all of the validation errors I should get plus some Generic ones like "User is invalid" and "Customer is invalid" If I iterate through the errors I get something like: user.login can't be blank User is invalid customer.whatever is blah blah blah...etc customer.some_other_error etc etc Since there is at least one invalid field in the nested User model, an extra "X is invalid" message is added to the list of errors. This gets confusing to my client and so I'm wondering if there is a quick way to do this instead of having to filer through the errors myself.

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• Entity Framework in layered architecture

  - by Kamyar

  I am using a layered architecture with the Entity Framework. Here's What I came up with till now (All the projects Except UI are class library): Entities: The POCO Entities. Completely persistence ignorant. No Reference to other projects. Generated by Microsoft's ADO.Net POCO Entity Generator. DAL: The EDMX (Entity Model) file with the context class. (t4 generated). References: Entities BLL: Business Logic Layer. Will implement repository pattern on this layer. References: Entities, DAL. This is where the objectcontext gets populated: var ctx=new DAL.MyDBEntities(); UI: The presentation layer: ASP.NET website. References: Entities, BLL + a connection string entry to entities in the config file (question #2). Now my three questions: Is my layer discintion approach correct? In my UI, I access BLL as follows: var customerRep = new BLL.CustomerRepository(); var Customer = customerRep.GetByID(myCustomerID); The problem is that I have to define the entities connection string in my UI's web.config/app.config otherwise I get a runtime exception. IS defining the entities connectionstring in UI spoils the layers' distinction? Or is it accesptible in a muli layered architecture. Should I take any additional steps to perform chage tracking, lazy loading, etc (by etc I mean the features that Entity Framework covers in a conventional, 1 project, non POCO code generation)? Thanks and apologies for the lengthy question.

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• Python unittest (using SQLAlchemy) does not write/update database?

  - by Jerry

  Hi, I am puzzled at why my Python unittest runs perfectly fine without actually updating the database. I can even see the SQL statements from SQLAlchemy and step through the newly created user object's email -- ...INFO sqlalchemy.engine.base.Engine.0x...954c INSERT INTO users (user_id, user_name, email, ...) VALUES (%(user_id)s, %(user_name)s, %(email)s, ...) ...INFO sqlalchemy.engine.base.Engine.0x...954c {'user_id': u'4cfdafe3f46544e1b4ad0c7fccdbe24a', 'email': u'[email protected]', ...} > .../tests/unit_tests/test_signup.py(127)test_signup_success() -> user = user_q.filter_by(user_name='test').first() (Pdb) n ...INFO sqlalchemy.engine.base.Engine.0x...954c SELECT users.user_id AS users_user_id, ... FROM users WHERE users.user_name = %(user_name_1)s LIMIT 1 OFFSET 0 ...INFO sqlalchemy.engine.base.Engine.0x...954c {'user_name_1': 'test'} > .../tests/unit_tests/test_signup.py(128)test_signup_success() -> self.assertTrue(isinstance(user, model.User)) (Pdb) user <pweb.models.User object at 0x9c95b0c> (Pdb) user.email u'[email protected]' Yet at the same time when I login to the test database, I do not see the new record there. Is it some feature from Python/unittest/SQLAlchemy/Pyramid/PostgreSQL that I'm totally unaware of? Thanks. Jerry

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• How do I set up routes to enable me to call different actions on the same controller?

  - by Remnant

  I am building my first asp.net mvc application for learning and development purposes and have come across an issue that I'd like some guidance with. Suppose I have a controller with two actions as follows: public class MyController : Controller { public ActionResult Index() { dbData = GetData("DefaultParameter") return View(dbData); } public ActionResult UpdateView(string dbParameter) { dbData = GetData("dbParameter"); return View(dbData); } } On my webpage I have the following: <% using (Html.BeginForm("UpdateView", "MyController")) %> <% { %> <div class="dropdown"><%=Html.DropDownList("Selection", Model.List, new { onchange="this.form.submit();" })%></div> <% } %> I have the following route in Global.asax: public static void RegisterRoutes(RouteCollection routes) { routes.MapRoute("Default", "{controller}", new { controller = "MyController", action = "Index"}); } The issue I am having is as follows: When I use the dropdownlist I get an error saying that /MyController/UpdateView could not be found. It therefore seems that I need to add an additional route as follows: routes.MapRoute("Default", "{controller}", new { controller = "MyController", action = "UpdateView"}); However, this causes two new issues for me: Due to the hierachy within the routing list, the similarity of the routes means that the one that appears first in the list is always executed. I don't see why I need to create another route for UpdateView. All I want to do is to retrieve new data from the database and update the view. I don't see what this has to do with the URL schema. It feels like I have gone down the wrong track here and I have missed something quite fundamental?

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• Dataset bind to Gridview within WCF REST retrieval method and Linq to Sql

  - by user643794

  I used a WCF REST template to build a WCF service library to create PUT and GET calls. PUT method works fine sending my blob to a database. On the GET, I want to be able to access the web service directly and display the results from a stored procedure as a dataset and bind this to a gridview. The stored procedure is a simple select statement, returning three of the four columns from the table. I have the following: [WebGet(UriTemplate = "/?name={name}", ResponseFormat = WebMessageFormat.Xml)] public List<Object> GetCollection(string name) { try { db.OpenDbConnection(); // Call to SQL stored procedure return db.GetCustFromName(name); } catch (Exception e) { Log.Error("Stored Proc execution failed. ", e); } finally { db.CloseDbConnection(); } return null; } I also added Linq to SQL class to include my database table and stored procedures access. I also created the Default.aspx file in addition to the other required files. protected void Page_Load(object sender, EventArgs e) { ServiceDataContext objectContext = new ServiceDataContext(); var source = objectContext.GetCustFromName("Tiger"); Menu1.DataSource = source; Menu1.DataBind(); } But this gives me The entity type '' does not belong to any registered model. Where should the data binding be done? What should be the return type for GetCollection()? I am stuck with this. Please provide help on how to do this.

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• Schema design: many to many plus additional one to many

  - by chrisj

  Hi, I have this scenario and I'm not sure exactly how it should be modeled in the database. The objects I'm trying to model are: teams, players, the team-player membership, and a list of fees due for each player on a given team. So, the fees depend on both the team and the player. So, my current approach is the following: **teams** id name **players** id name **team_players** id player_id team_id **team_player_fees** id team_players_id amount send_reminder_on Schema layout ERD In this schema, team_players is the junction table for teams and players. And the table team_player_fees has records that belong to records to the junction table. For example, playerA is on teamA and has the fees of $10 and $20 due in Aug and Feb. PlayerA is also on teamB and has the fees of $25 and $25 due in May and June. Each player/team combination can have a different set of fees. Questions: Are there better ways to handle such a scenario? Is there a term for this type of relationship? (so I can google it) Or know of any references with similar structures?

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• Is there a way to set two C#.Net projects to trust one another?

  - by Eric

  I have two C#.NET projects in a single solution ModelProject and PluginProject. PlugInProject is a plug-in for another application, and consequently references its API. PlugInProject is used to extract data from the application it plugs into. ModelProject contains the data model of classes that are extracted by PlugInProject. The extracted data can be used independent of the application or the plug-in, which is why I am keeping PlugInProject separate from ModelProject. I want ModelProject to remain independent of PlugInProject, and the Applications API. Or in other words I want someone to be able to access the extracted data without needing access to PlugInProject, the application, or the application's API. The problem I'm running into though is PlugInProject needs to be able to create and modify classes in ModelProject. However, I'd prefer to not make these actions public to anyone using ModelProject. The extracted data should effectively be read-only, unless later modified by PlugInProject. How can I keep these projects separate but give PlugInProject exclusive access to ModelProject? Is this possible?

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• Alternatives to the Entity Framework for Serving/Consuming an OData Interface

  - by Egahn

  I'm researching how to set up an OData interface to our database. I would like to be able to pull/query data from our DB into Excel, as a start. Eventually I would like to have Excel run queries and pull data over HTTP from a remote client, including authentication, etc. I've set up a working (rickety) prototype so far, using the ADO.NET Entity Data Model wizard in Visual Studio, and VSTO to create a test Excel worksheet with a button to pull from that ADO.NET interface. This works OK so far, and I can query the DB using Linq through the entities/objects that are created by the ADO.NET EDM wizard. However, I have started to run into some problems with this approach. I've been finding the Entity Framework difficult to work with (and in fact, also difficult to research solutions to, as there's a lot of chaff out there regarding it and older versions of it). An example of this is my being unable to figure out how to set the SQL command timeout (as opposed to the HTTP request timeout) on the DataServiceContext object that the wizard generates for my schema, but that's not the point of my question. The real question I have is, if I want to use OData as my interface standard, am I stuck with the Entity Framework? Are there any other solutions out there (preferably open source) which can set up, serve and consume an OData interface, and are easier to work with and less bloated than the Entity Framework? I have seen mention of NHibernate as an alternative, but most of the comparison threads I've seen are a few years old. Are there any other alternatives out there now? Thanks very much!

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• Ditching Django's models for Ajax/Web Services

  - by Igor Ganapolsky

  Recently I came across a problem at work that made me rethink Django's models. The app I am developing resides on a Linux server. Its a simple model/view/controller app that involves user interaction and updating data in the database. The problem is that this data resides in a MS SQL database on a Windows machine. So in order to use Django's models, I would have to leverage an ODBC driver on linux, and the use a python add-on like pyodbc. Well, let me tell you, setting up a reliable and functional ODBC connection on linux is no easy feat! So much so, that I spent several hours maneuvering this on my CentOS with no luck, and was left with frustration and lots of dumb system errors. In the meantime I have a deadline to meet, and suddenly the very agile and rapid Django application is a roadblock rather than a pleasure to work with. Someone on my team suggested writing this app in .NET. But there are a few problems with that: it won't be deployable on a linux machine, and I won't be able to work on it since I don't know ASP.net. Then a much better suggestion was made: keep the app in django, but instead of using models, do straight up ajax/web services calls in the template. And then it dawned on me - what a great idea. Django's models seem like a nuissance and hindrance in this case, and I can just have someone else write .Net services on their side, that I can call from my template. As a result my app will be leaner and more compact. So, I was wondering if you guys ever came across a similar dillema and what you decided to do about it.

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• Why is Core Data not persisting these changes to disk?

  - by scott

  I added a new entity to my model and it loads fine but no changes made in memory get persisted to disk. My values set on the car object work fine in memory but aren't getting persisted to disk on hitting the home button (in simulator). I am using almost exactly the same code on another entity in my application and its values persist to disk fine (core data - sqlite3); Does anyone have a clue what I'm overlooking here? Car is the managed object, cars in an NSMutableArray of car objects and Car is the entity and Visible is the attribute on the entity which I am trying to set. Thanks for you assistance. Scott - (void)viewDidLoad { myAppDelegate* appDelegate = (myAppDelegate*)[[UIApplication sharedApplication] delegate]; NSManagedObjectContext* managedObjectContex = appDelegate.managedObjectContext; NSFetchRequest* request = [[NSFetchRequest alloc] init]; NSEntityDescription* entity = [NSEntityDescription entityForName:@"Car" inManagedObjectContext:managedObjectContex]; [request setEntity:entity]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Name" ascending:YES]; NSArray* sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [request setSortDescriptors:sortDescriptors]; [sortDescriptors release]; [sortDescriptor release]; NSError* error = nil; cars = [[managedObjectContex executeFetchRequest:request error:&error] mutableCopy]; if (cars == nil) { NSLog(@"Can't load the Cars data! Error: %@, %@", error, [error userInfo]); } [request release]; } - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath*)indexPath { Car* car = [cars objectAtIndex:indexPath.row]; if (car.Visible == [NSNumber numberWithBool:YES]) { car.Visible = [NSNumber numberWithBool:NO]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryNone; } else { car.Visible = [NSNumber numberWithBool:YES]; [tableView cellForRowAtIndexPath:indexPath].accessoryType = UITableViewCellAccessoryCheckmark; } }

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• CQRS and email notification

  - by t0PPy

  Reading up on CQRS there is a lot of talk of email notification - i'm wondering where to get the data from. Imagine a senario where one user invites other users to an event. To inform a user that he has been invitet to an event, he is send an email. The concrete mecanics might go like this: A "CreateEvent" command with an associated collection of user to invite, is received by the server. A new meeting aggregate is created and a method "InviteUser" is called for each user that is to be invited. Each time a user is invited to an event, a domain event "UserWasInvitedToEvent" is raised. An email notification sender picks up the domain event and sends out the notification email. Now my question is this: Where do i go for information to include in the email? Say i want to include a description of the event as well as the users name. Since this is CQRS i can't get it thru my domain model; All the properties of the domain objects are private! Should i then query the write side? Or maybe move email notification to a different service entirely? Any thoughts will be much appriciated!

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• How to define multiple elements in XML Schema with the same name and different attribute value allow

  - by David Skyba

  I would like to create XML Schema for this chunk of xml, I would like to restrict the values of "name" attribute, so that in output document on and only one instance of day is allowed for each week day: <a> <day name="monday" /> <day name="tuesday" /> <day name="wednesday" /> </a> I have tried to use this: <xs:complexType name="a"> <xs:sequence> <xs:element name="day" minOccurs="1" maxOccurs="1"> <xs:complexType> <xs:attribute name="name" use="required"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="monday" /> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> <xs:element name="day" minOccurs="1" maxOccurs="1"> <xs:complexType> <xs:attribute name="name" use="required"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="tuesday" /> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> but XML Schema validator in eclipse says error "Multiple elements with name 'day', with different types, appear in the model group.". Is there any other way?

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• Redirecting from an update action to the referrer of the edit

  - by Mark Westling

  My Rails 2.3 application has a User model and the usual controller actions. The edit form can be reached two ways: when a user edits his own profile from the home page, or when an admin user edits someone else's profile from users collection. What I'd like to do is have the update action redirect back to the referred of the edit action, not the update action. If I do a simple redirect_to(:back) within update, it goes back to the edit form -- not good. One solution is to forget entirely about referrers and redirect based on the current_user and the updated user: if they're the same, go back to the home page, else go to the users collection page. This will break if I ever add a third path to the edit form. It's doubtful I'll ever do this but I'd prefer a solution that's not so brittle. Another solution is to store the referrer of edit form in a hidden field and then redirect to this value from inside the update action. This doesn't feel quite right, though I can't explain why. Are there any better approaches? Or, should I stop worrying and go with one of the two I've mentioned?

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