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  • Generic <T> how cast ?

    - by Kris-I
    Hi, I have a "Product" base class, some other classes "ProductBookDetail","ProductDVDDetail" inherit from this class. I use a ProductService class to make operation on these classes. But, I have to do some check depending of the type (ISBN for Book, languages for DVD). I'd like to know the best way to cast "productDetail" value, I receive in SaveOrupdate. I tried GetType() and cast with (ProductBookDetail)productDetail but that's not work. Thanks, var productDetail = new ProductDetailBook() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailBook>>(); service.SaveOrUpdate(productDetail); var productDetail = new ProductDetailDVD() { .... }; var service = IoC.Resolve<IProductServiceGeneric<ProductDetailDVD>>(); service.SaveOrUpdate(productDetail); public class ProductServiceGeneric<T> : IProductServiceGeneric<T> { private readonly ISession _session; private readonly IProductRepoGeneric<T> _repo; public ProductServiceGeneric() { _session = UnitOfWork.CurrentSession; _repo = IoC.Resolve<IProductRepoGeneric<T>>(); } public void SaveOrUpdate(T productDetail) { using (ITransaction tx = _session.BeginTransaction()) { //here i'd like ot know the type and access properties depending of the class _repo.SaveOrUpdate(productDetail); tx.Commit(); } } }

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  • Access to field in extended flatpage in django

    - by Stanislav Feldman
    How to access field in extended flatpage in django? I wrote this: class ExtendedFlatPage(FlatPage): teaser = CharField(max_length=150) class ExtendedFlatPageForm(FlatpageForm): teaser = CharField(max_length=150) class Meta: model = ExtendedFlatPage class ExtendedFlatPageAdmin(FlatPageAdmin): form = ExtendedFlatPageForm fieldsets = ( (None, {'fields': ('url', 'title', 'teaser', 'content', 'sites',)}), ) admin.site.unregister(FlatPage) admin.site.register(ExtendedFlatPage, ExtendedFlatPageAdmin) And creation in admin is ok. But then in flatpages/default.html I tried this: <html> <body> <h1>{{ flatpage.title }}</h1> <strong>{{ flatpage.teaser }}</strong> <p>{{ flatpage.content }}</p> </body> </html> And there was no flatpage.teaser! What is wrong?

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  • What is Ruby's double-colon (::) all about?

    - by Meltemi
    I'd probably be able to answer this for myself if "::" wasn't so hard to Google. Didn't see anything on SO so thought I'd try my luck. What is this double-colon :: all about? I see it everywhere in Rails: class User < ActiveRecord::Base or… ActionController::Routing::Routes.draw do |map| I found a definition from this guy: The :: is a unary operator that allows: constants, instance methods and class methods defined within a class or module, to be accessed from anywhere outside the class or module. but that just leads to more questions. What good is scope (private, protected) if you can just use :: to expose anything?

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  • How do I get events to execute on the "main thread"

    - by William DiStefano
    I have 2 classes, one is frmMain a windows form and the other is a class in vb.NET 2003. frmMain contains a start button which executes the monitor function in the other class. My question is, I am manually adding the event handlers -- when the events are executed how do I get them to excute on the "main thread". Because when the tooltip balloon pops up at the tray icon it displays a second tray icon instead of popping up at the existing tray icon. I can confirm that this is because the events are firing on new threads because if I try to display a balloon tooltip from frmMain it will display on the existing tray icon. Here is a part of the second class (not the entire thing): Friend Class monitorFolders Private _watchFolder As System.IO.FileSystemWatcher = New System.IO.FileSystemWatcher Private _eType As evtType Private Enum evtType changed created deleted renamed End Enum Friend Sub monitor(ByVal path As String) _watchFolder.Path = path 'Add a list of Filter to specify _watchFolder.NotifyFilter = IO.NotifyFilters.DirectoryName _watchFolder.NotifyFilter = _watchFolder.NotifyFilter Or IO.NotifyFilters.FileName _watchFolder.NotifyFilter = _watchFolder.NotifyFilter Or IO.NotifyFilters.Attributes 'Add event handlers for each type of event that can occur AddHandler _watchFolder.Changed, AddressOf change AddHandler _watchFolder.Created, AddressOf change AddHandler _watchFolder.Deleted, AddressOf change AddHandler _watchFolder.Renamed, AddressOf Rename 'Start watching for events _watchFolder.EnableRaisingEvents = True End Sub Private Sub change(ByVal source As Object, ByVal e As System.IO.FileSystemEventArgs) If e.ChangeType = IO.WatcherChangeTypes.Changed Then _eType = evtType.changed notification() End If If e.ChangeType = IO.WatcherChangeTypes.Created Then _eType = evtType.created notification() End If If e.ChangeType = IO.WatcherChangeTypes.Deleted Then _eType = evtType.deleted notification() End If End Sub Private Sub notification() _mainForm.NotifyIcon1.ShowBalloonTip(500, "Folder Monitor", "A file has been " + [Enum].GetName(GetType(evtType), _eType), ToolTipIcon.Info) End Sub End Class

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  • "Inherited" types in C++

    - by Ken Moynihan
    The following code does not compile. I get an error message: error C2039: 'Asub' : is not a member of 'C' Can someone help me to understand this? Tried VS2008 & 2010 compiler. template <class T> class B { typedef int Asub; public: void DoSomething(typename T::Asub it) { } }; class C : public B<C> { public: typedef int Asub; }; class A { public: typedef int Asub; }; int _tmain(int argc, _TCHAR* argv[]) { C theThing; theThing.DoSomething(C::Asub()); return 0; }

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  • What is the purpose of unit testing an interface repository

    - by ahsteele
    I am unit testing an ICustomerRepository interface used for retrieving objects of type Customer. As a unit test what value am I gaining by testing the ICustomerRepository in this manner? Under what conditions would the below test fail? For tests of this nature is it advisable to do tests that I know should fail? i.e. look for id 4 when I know I've only placed 5 in the repository I am probably missing something obvious but it seems the integration tests of the class that implements ICustomerRepository will be of more value. [TestClass] public class CustomerTests : TestClassBase { private Customer SetUpCustomerForRepository() { return new Customer() { CustId = 5, DifId = "55", CustLookupName = "The Dude", LoginList = new[] { new Login { LoginCustId = 5, LoginName = "tdude" }, new Login { LoginCustId = 5, LoginName = "tdude2" } } }; } [TestMethod] public void CanGetCustomerById() { // arrange var customer = SetUpCustomerForRepository(); var repository = Stub<ICustomerRepository>(); // act repository.Stub(rep => rep.GetById(5)).Return(customer); // assert Assert.AreEqual(customer, repository.GetById(5)); } } Test Base Class public class TestClassBase { protected T Stub<T>() where T : class { return MockRepository.GenerateStub<T>(); } } ICustomerRepository and IRepository public interface ICustomerRepository : IRepository<Customer> { IList<Customer> FindCustomers(string q); Customer GetCustomerByDifID(string difId); Customer GetCustomerByLogin(string loginName); } public interface IRepository<T> { void Save(T entity); void Save(List<T> entity); bool Save(T entity, out string message); void Delete(T entity); T GetById(int id); ICollection<T> FindAll(); }

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  • Python hash() can't handle long integer?

    - by Xie
    I defined a class: class A: ''' hash test class a = A(9, 1196833379, 1, 1773396906) hash(a) -340004569 This is weird, 12544897317L expected. ''' def __init__(self, a, b, c, d): self.a = a self.b = b self.c = c self.d = d def __hash__(self): return self.a * self.b + self.c * self.d Why, in the doctest, hash() function gives a negative integer?

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  • How to treat Base* pointer as Derived<T>* pointer?

    - by dehmann
    I would like to store pointers to a Base class in a vector, but then use them as function arguments where they act as a specific class, see here: #include <iostream> #include <vector> class Base {}; template<class T> class Derived : public Base {}; void Foo(Derived<int>* d) { std::cerr << "Processing int" << std::endl; } void Foo(Derived<double>* d) { std::cerr << "Processing double" << std::endl; } int main() { std::vector<Base*> vec; vec.push_back(new Derived<int>()); vec.push_back(new Derived<double>()); Foo(vec[0]); Foo(vec[1]); delete vec[0]; delete vec[1]; return 0; } This doesn't compile: error: call of overloaded 'Foo(Base*&)' is ambiguous Is it possible to make it work? I need to process the elements of the vector differently, according to their int, double, etc. types.

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  • Hibernate @Transactional not starting transaction

    - by rhinds
    I have a web app using Hibernate, and I am attempting to persist some data, but it is failing to persist within a Transaction despite using the @Transactional annotation. My service class is as follows: @Service("profileService") public class ProfileService { private EntityManager entityManager; @Autowired private AccountService accountService; @Autowired private ProfileDAOImpl profileDao; @PersistenceContext public void setEntityManager(EntityManager em) { this.entityManager = em; } @Transactional public void addConnectionToAccount(SocialConnection sc) { entityManager.persist(sc); } } The addConnectionToAccount() method is being called from another Spring bean in a normal method, and the ProfileService class is currently being injected there: public class HibernateConnectionRepository implements ConnectionRepository { @Inject private ProfileService profileService; @Override @Transactional public void addConnection(SocialConnection sc) { try { profileService.addConnectionToAccount(accountId, sc); } catch (Exception e) { e.printStackTrace(); } } I tried putting the @Transactional annotation on the calling method in the vain hope that it might make a difference but nothing. Previously I have experienced problems like this its been because the object being persisted does not satisfy table restrictions (such as non-nullable columns as null) or because the method is being called from within the same class and the calling method is not Transactional, but neither of those are the case here.. Any ideas? it just fails silently, the logs are as follows: 2012-03-26 22:25:04,702 [http-bio-8085-exec-9] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@1bc25c8 [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@e5b006) 2012-03-26 22:25:04,710 [http-bio-8085-exec-9] DEBUG org.hibernate.SQL - select SEQ_COUNT from SEQUENCE where SEQ_NAME = 'PO_SEQ' for update 2012-03-26 22:25:04,711 [http-bio-8085-exec-9] DEBUG org.hibernate.SQL - update SEQUENCE set SEQ_COUNT = ? where SEQ_COUNT = ? and SEQ_NAME = 'PO_SEQ' 2012-03-26 22:25:04,723 [http-bio-8085-exec-9] DEBUG com.mchange.v2.resourcepool.BasicResourcePool - trace com.mchange.v2.resourcepool.BasicResourcePool@1bc25c8 [managed: 3, unused: 2, excluded: 0] (e.g. com.mchange.v2.c3p0.impl.NewPooledConnection@e5b006) 2012-03-26 22:25:04,723 [http-bio-8085-exec-9] DEBUG org.hibernate.event.internal.AbstractSaveEventListener - Generated identifier: 2200, using strategy: org.hibernate.id.MultipleHiLoPerTableGenerator UPDATE Also wanted to mention that the HibernateConnectionRepository bean is not annotated and is actually being configured in an @Configuration class (if this makes any difference? not used @Configuration classes much). The method to create the bean is as follows: @Bean @Scope(value = "request", proxyMode = ScopedProxyMode.INTERFACES) public ConnectionRepository connectionRepository() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); if (authentication == null) { throw new IllegalStateException("Unable to get a ConnectionRepository: no user signed in"); } ApplicationUser user = (ApplicationUser) authentication.getPrincipal(); return usersConnectionRepository().createConnectionRepository(String.valueOf(user.getAccountId())); } The bean is scoped to the logged in user, but may also be created multiple times for each user..

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  • Accessing data entered into multiple Django forms and generating them onto a new URL

    - by pedjk
    I have a projects page where users can start up new projects. Each project has two forms. The two forms are: class ProjectForm(forms.Form): Title = forms.CharField(max_length=100, widget=_hfill) class SsdForm(forms.Form): Status = forms.ModelChoiceField(queryset=P.ProjectStatus.objects.all()) With their respective models as follows: class Project(DeleteFlagModel): Title = models.CharField(max_length=100) class Ssd(models.Model): Status = models.ForeignKey(ProjectStatus) Now when a user fills out these two forms, the data is saved into the database. What I want to do is access this data and generate it onto a new URL. So I want to get the "Title" and the "Status" from these two forms and then show them on a new page for that one project. I don't want the "Title" and "Status" from all the projects to show up, just for one project at a time. If this makes sense, how would I do this? I'm very new to Django and Python (though I've read the Django tutorials) so I need as much help as possible. Thanks in advance Edit: The ProjectStatus code is (under models): class ProjectStatus(models.Model): Name = models.CharField(max_length=30) def __unicode__(self): return self.Name

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  • Best way to implement game loop without freezing UI thread

    - by Matt H
    I'm trying to make a simple 2D game in Java. So far I have a JFrame, with a menubar, and a class which extends JPanel and overrides it's paint method. Now, I need to get a game loop going, where I will update the position of images and so on. However, I'm stuck at how best to achieve this. Should I use multi-threading, because surely, if you put an infinite loop on the main thread, the UI (and thus my menu bar) will freeze up? Here's my code so far: import java.awt.Color; import java.awt.Graphics; import javax.swing.JPanel; @SuppressWarnings("serial") public class GameCanvas extends JPanel { public void paint(Graphics g) { while (true) { g.setColor(Color.DARK_GRAY); try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } } } } import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; @SuppressWarnings("serial") public class Main extends JFrame { GameCanvas canvas = new GameCanvas(); final int FRAME_HEIGHT = 400; final int FRAME_WIDTH = 400; public static void main(String args[]) { new Main(); } public Main() { super("Game"); JMenuBar menuBar = new JMenuBar(); JMenu fileMenu = new JMenu("File"); JMenuItem startMenuItem = new JMenuItem("Pause"); menuBar.add(fileMenu); fileMenu.add(startMenuItem); super.add(canvas); super.setVisible(true); super.setSize(FRAME_WIDTH, FRAME_WIDTH); super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); super.setJMenuBar(menuBar); } } Any pointers/tips? Also, where should I put my loop? In my main class, or my GameCanvas class? Any help is appreciated, thanks.

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  • Overwrite queryset which builds filter sidebar

    - by cw
    Hi, I'm writing a hockey database/manager. So I have the following models: class Team(models.Model): name = models.CharField(max_length=60) class Game(models.Model): home_team = models.ForeignKey(Team,related_name='home_team') away_team = models.ForeignKey(Team,related_name='away_team') class SeasonStats(models.Model): team = models.ForeignKey(Team) Ok, so my problem is the following. There are a lot of teams, but Stats are just managed for my Club. So if I use "list_display" in the admin backend, I'd like to modify/overwrite the queryset which builds the sidebar for filtering, to just display our home teams as a filter option. Is this somehow possible in Django? I already made a custom form like this class SeasonPlayerStatsAdminForm(forms.ModelForm): team = forms.ModelChoiceField(Team.objects.filter(club__home=True)) So now just the filtering is missing. Any ideas?

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  • JQuery nth-child not working properly

    - by Keith Donegan
    Hi Guys, I am using JQuery's nth-child selector to alter the margin on every 3rd div with a class of photo_post_thumbnail, but it alters it every 2nd div? Can anyone spot what I am doing wrong? Site http://www.clients.eirestudio.net/hatstand/wordpress/photos/ HTML markup <div class="postbox photo_post_thumbnail"> blah blah </div> <div class="postbox photo_post_thumbnail"> blah blah </div> <div class="postbox photo_post_thumbnail"> blah blah </div> JQuery Code $('.photo_post_thumbnail:nth-child(3n)').css('margin-right', '0px');

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  • Shared static classes between AppDomains in loaded library code

    - by Christian Stewart
    I'm working on a program in which I want to do something similar to what the Photon Server system does: Offer a common "API" class library, which contains common data classes, enumerations, and interfaces for working with the host program. Have client programs (class libraries) reference this DLL and implement interfaces listed within it. Have the "host" application load built DLL client libraries into separate AppDomains and reference the interfaces that lie within to have polymorphic client code from within a dll file. I have something like this worked out: a class library that contains common code, but I've run into the following question How should I handle static classes? Should I add a method that is called by the host program to synchronize data? How do I keep a static class the same between AppDomains? Should I discard these classes in favor of better interfaces between the code levels? And in general, how do I share data between these loaded AppDomains?

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  • open Fancybox in tabs

    - by Prashant
    Hello all. I am using PHP + jQuery + Fancybox in my project. I have multiple tabs that get created dynamically. I have got a star icon on every tab header and on clicking them I want to open a fancybox. My tabs are basically ul-li with following dynamic code. $("#tabs").append("<li class='current'><a class='tab' id='tab_" + tabCnt + "<a href='#loginBox_div' class='login_link'> <img src='star.png' style='cursor:pointer'/> </a>" + "<a href='javascript:void(0);' class='remove'>x</a></li>"); in my index file : $(document).ready(function() { $("a.login_link").fancybox({ 'titlePosition' : 'inside', 'transitionIn' : 'none', 'transitionOut' : 'none' }); }); The problem is that when I click on star icon of first tab, the loginBox_div (fancybox) opens properly. But when my second tab is created and when I click on its star icon, the fancybox is not opening although the class is applied in second and successive tabs. No javascript errors too. Please show me the way. Thank you.

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  • Wierdness debugging Visual Studio C++ 2008

    - by Jeff Dege
    I have a legacy C++ app, that in its most incarnation we've been building with makefiles and VS2003's command-line tool. I'm trying to get it to build using VS2008 and MsBuild. The build is working OK, but I'm getting errors where I'd never seen errors, before, and stepping through in VS2008's debugger only confuses me. The app links a number of static libraries, which fall into two categories: those that are part of the same application suite, and those that are shared between a number of application suites. Originally, I had a .csproj file for each static library, and two .sln files, one for the application suite (including the suite-specific libraries) and one for the non-suite-specific shared libraries. The shared libraries were included in the link, their projects were not included in the application suite .sln. The application instantiates an object from a class that is defined in one of the shared libraries. The class has a member object of a class that wraps a linked list. The constructor of the linked list class sets its "head" pointer to null. When I run the app, and try to add an element to the linked list, I get an error - the head pointer contains the value 0xCCCCCCCC. So I step through with the debugger. And see weirdness. When the current line in the debugger is in a source file belonging to the static library, the head pointer contains 0x00000000. When I step into the constructor, I can see the pointer being set to that value, and when I'm stepped into any other method of the class, I can see that the head pointer still contains 0x00000000. But when I step out into methods that are defined in the application suite .sln, it contains 0xCCCCCCCC. It's not like it's being overwritten. It changes back and forth depending upon which source file I am currently debugging. So I included the shared library's project in the application suite .sln, and now I see the head pointer containing 0xCCCCCCCC all the time. It looks like the constructor of the linked list class is not being called. So now, I'm entirely confused. Anyone have any ideas?

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  • Javascript and VERY LONG string

    - by StealthRT
    Hey all, i am having problems with the below code: function showTableData() { var tableArray; var x = 0; var theHTML; for (i = 0; i < 7032; i++) { if (x = 0) { theHTML = '<tr>' + '<th scope="row" class="spec">' + partNum[i] + '</th>' + '<td>' + Msrp[i] + '</td>' + '<td>' + blah[i] + '</td>' + '<td>' + blahs[i] + '</td>' + '</tr>' + theHTML; x++; }else{ theHTML = '<tr>' + '<th scope="row" class="specalt">' + partNum[i] + '</th>' + '<td class="alt">' + Msrp[i] + '</td>' + '<td class="alt">' + blah[i] + '</td>' + '<td class="alt">' + blahs[i] + '</td>' + '</tr>' + theHTML; x--; } } theHTML = '<table id="mytable" cellspacing="0">' + '<tr>' + '<th scope="col" abbr="Configurations" class="nobg">Part Number</th>' + '<th scope="col" abbr="Dual 1.8">Msrp Price</th>' + '<th scope="col" abbr="Dual 2">blahs Price</th>' + '<th scope="col" abbr="Dual 2.5">Low Price</th>' + '</tr>' + theHTML + '</table>'; $('#example').append(theHTML); } </script> <div id="example"> </div> The problem being that the $('#example').append(theHTML); never executes (or shows on the page). I think its because the string is soooooo long! It has over 7,000 items in the array so im not sure if thats the reason or if its something else? Any help would be great! Thanks! David

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  • mysql eliminate responses under certain condition with join

    - by Dustin
    Forgive me if this is an easy question. I teach classes and want to be able to select those students who have taken one class, but not another class. I have two tables: lessons_slots which is the table for every class such as: -------------------- -ID name slots- -1 basics 10 - -2 advanced 10 - -3 basics 10 - --------------------- The other table is class_roll, which holds enrollment info, such as: -------------------- -sID classid firstname lastname- -1 1 Jo Schmo -2 1 Person Two ... -13 2 Jo Schmo --------------------- What I want to do, I select everyone who has not had the advanced class (for example). I've tried doing SELECT * FROM lessons_slots LEFT JOIN class_roll ON lessons_slots.ID = class_roll.classid WHERE lessons_slots.name != 'advanced' But that doesn't work. Any ideas?

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  • ADO Exception in HQL query

    - by Yoav
    I have 2 classes: Project and DataStructure. Class Project contains member List<DataStructure. My goal is to load a Project and all its DataStructures in one call. public class Project { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual ISet<DataStructure> DataStructures { get { } set { } } } public class DataStructure { public virtual string Id { get { } set { } } public virtual string Name { get { } set { } } public virtual string Description { get { } set { } } public virtual Project Project { get { } set { } } public virtual IList<DataField> Fields { get { } set { } } } Note that DataStructure also contains a list of class DataField but I don’t want to load these right now. Mapping in Fluent NHibernate: public class ProjectMap : ClassMap<Project> { public ProjectMap() { Table("PROJECTS"); Id(x => x.Pk, "PK"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); HasMany<DataStructure>(x => x.DataStructures).KeyColumn("FK_PROJECT"); } } public class DataStructureMap : ClassMap<DataStructure> { public DataStructureMap() { Table("DATA_STRUCTURES"); Map(x => x.Id, "ID"); Map(x => x.Name, "NAME"); Map(x => x.Description, "DESCRIPTION"); References<Project>(x => x.Project, "FK_PROJECT"); HasMany<DataField>(x => x.Fields).KeyColumn("FK_DATA_STRUCTURE"); } } This is my query: using (ISession session = SessionFactory.OpenSession()) { IQuery query = session.CreateQuery("from Project pr left join pr.DataStructure"); project = query.List<Project>(); } query.List() returns this exception: NHibernate.Exceptions.GenericADOException: Could not execute query[SQL: SQL not available] ---> System.ArgumentException: The value "System.Object[]" is not of type "Project" and cannot be used in this generic collection.

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  • Log information inside a JUnit Suite

    - by Alex Marinescu
    I'm currently trying to write inside a log file the total number of failed tests from a JUnite Suite. My testsuite is defined as follows: @RunWith(Suite.class) @SuiteClasses({Class1.class, Class2.class etc.}) public class SimpleTestSuite {} I tried to define a rule which would increase the total number of errors when a test fails, but apparently my rule is never called. @Rule public MethodRule logWatchRule = new TestWatchman() { public void failed(Throwable e, FrameworkMethod method) { errors += 1; } public void succeeded(FrameworkMethod method) { } }; Any ideas on what I should to do to achieve this behaviour?

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  • Select CSS based on multiple classes

    - by Stacey
    I have a style rule I want to apply to a tag when it has TWO styles. Is there any way to perform this without javascript? In other words.. <li class='left ui-class-selector'> I want to select only if the li has both 'left' and 'ui-class-selector' classes applied.

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  • C# Virtual method call in constructor - how to refactor?

    - by Cristi Diaconescu
    I have an abstract class for database-agnostic cursor actions. Derived from that, there are classes that implement the abstract methods for handling database-specific stuff. The problem is, the base class ctor needs to call an abstract method - when the ctor is called, it needs to initialize the database-specific cursor. I know why this shouldn't be done, I don't need that explanation! This is my first implementation, that obviously doesn't work - it's the textbook "wrong way" of doing it. The overridden method accesses a field from the derived class, which is not yet instantiated: public abstract class CursorReader { private readonly int m_rowCount; protected CursorReader() { m_rowCount = CreateCursor(sqlCmd); //virtual call ! } protected abstract int CreateCursor(string sqlCmd); } public class SqlCursorReader : CursorReader { private SqlConnection m_sqlConnection; public SqlCursorReader(string sqlCmd, SqlConnection sqlConnection) { m_sqlConnection = sqlConnection; //field initialized here } protected override int CreateCursor(string sqlCmd) { //uses not-yet-initialized member *m_sqlConnection* //so this throws a NullReferenceException var cursor = new CustomCursor(sqlCmd, m_sqlConnection); return cursor.Count(); } } I will follow up with an answer on my attempts to fix this...

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  • Does this code describe an Existential Type in C#?

    - by noblethrasher
    Currently watching Bart De Smet's explanation of IQueryable and he mentioned Existential Types (which I've been curious about for some time). After reading the answers to this question I'm just wondering if this is a way to construct it in C#: public abstract class ExistentialType { private ExistentialType() { } public abstract int Foo(); public ExistentialType Create() { return new ConcreateType1(); } private class ConcreateType1 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType2 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } private class ConcreateType3 : ExistentialType { public override int Foo() { throw new NotImplementedException(); } } }

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