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• Should I be learning Linq, Direct SQL Commands (in .net), EF or other?

  - by Wil

  Basically, I have a very good knowledge of plain old SQL coming from Classic ASP programming. Over the past couple of months, I have been learning C# and today was my first full day at MVC 3 (Razor) which I am loving! I need to get back in to Databases and I know that writing SqlCommand everywhere is obviously outdated (although it is nice I can still do it!). I used to go to a great usergroup as an IT Pro and the developer stuff went completely over my head, however I do remember a few things which kept coming up such as LINQ... However, that was some time ago and now the same people on Twitter are saying how out dated it is. I have tried to do research on both and I am clueless as to what direction I should go in, or when to use one over another (if learning both is a good thing). I am more so confused as I thought EF was a part of the .Net Framework, however, reading through the quick start guide, I had to download a component using Nuget. ... Basically I am out of my depth here and just need some honest advice of where to go!

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• Why DbContext object shouldn't be referred in Service Layer?

  - by nazmoonnoor

  I've been looking for some implementations of Service Layer and Controller interaction in blogs and in some open source projects. All of them seem to refer DbContext object in repository classes but avoided to use in service classes. Service classes essentially using a IQueryable<T> references of DbSet<T>. I want to know why this practice is good and why DbContext shouldn't have a reference in Service Layer.

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• Could you give me an example of how to attach an object in Deleted state – I keep getting an exception [migrated]

  - by carewithl

  From MSDN : An object in the Deleted state can only be attached when the ObjectStateManager is already tracking the relationship instance. Could you give me an example of how to attach an object in the Deleted state. I tried the following and got "System.InvalidOperationException: The object being attached is in an added or deleted state. Relationships cannot be created for objects in this state". var contact = context.Contacts.First(); Console.WriteLine(contact.Addresses.Count()); // 2 var address = contact.Addresses.First(); context.Addresses.DeleteObject(address); contact.Addresses.Attach(address); // InvalidOperationException thank you

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• Are elements returned by Linq-to-Entities query streamed from the DB one at the time or are they retrieved all at once?

  - by carewithl

  Are elements returned by Linq-to-Entities query streamed from the database one at the time ( as they are requested ) or are they retrieved all at once: SampleContext context = new SampleContext(); // SampleContext derives from ObjectContext var search = context.Contacts; foreach (var contact in search) { Console.WriteLine(contact.ContactID); // is each Contact retrieved from the DB // only when foreach requests it? } thank you in advance

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• ASP.Net Entity Framework, objectcontext error

  - by Chris Klepeis

  I'm building a 4 layered ASP.Net web application. The layers are: Data Layer Entity Layer Business Layer UI Layer The entity layer has my data model classes and is built from my entity data model (edmx file) in the datalayer using T4 templates (POCO). The entity layer is referenced in all other layers. My data layer has a class called SourceKeyRepository which has a function like so: public IEnumerable<SourceKey> Get(SourceKey sk) { using (dmc = new DataModelContainer()) { var query = from SourceKey in dmc.SourceKeys select SourceKey; if (sk.sourceKey1 != null) { query = from SourceKey in query where SourceKey.sourceKey1 == sk.sourceKey1 select SourceKey; } return query; } } Lazy loading is disabled since I do not want my queries to run in other layers of this application. I'm receiving the following error when attempting to access the information in the UI layer: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection. I'm sure this is because my DataModelContainer "dmc" was disposed. How can I return this IEnumerable object from my data layer so that it does not rely on the ObjectContext, but solely on the DataModel? Is there a way to limit lazy loading to only occur in the data layer?

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• Appengine datastore phantom entity - inconsistent state?

  - by aloo

  Getting a weird error on java appengine code that used to work fine (nothing has changed but the data in the datastore). I'm trying to iterate over the results of a query and change a few properties of the entities. The query does return a set of results, however, when I try to access the first result in the list, it throws an exception when trying to access any of its properties (but its key). Here's the exception: org.datanucleus.state.JDOStateManagerImpl isLoaded: Exception thrown by StateManager.isLoaded Could not retrieve entity of kind OnTheCan with key OnTheCan(3204258) org.datanucleus.exceptions.NucleusObjectNotFoundException: Could not retrieve entity of kind OnTheCan with key OnTheCan(3204258) at org.datanucleus.store.appengine.DatastoreExceptionTranslator.wrapEntityNotFoundException(DatastoreExceptionTranslator.java:60) And here is my code: PersistenceManager pm = PMF.get().getPersistenceManager(); Query query = null; List<OnTheCan> cans; query = pm.newQuery("SELECT this FROM " + OnTheCan.class.getName() + " WHERE open == true ORDER BY onTheCanId ASC"); query.setRange(0, num); cans = (List<OnTheCan>) query.execute(); for (OnTheCan c : cans) { System.err.println(c.getOnTheCanId()); // this works fine! getting the key works c.setOpen(false); // failure here with the above exception c.setAutoClosed(true); c.setEndTime(new Date(c.getStartTime().getTime() + 600000/*10*60*1000*/)); } pm.close(); The code throws the exception when trying to execute c.setOpen(false) - thats the first time I'm accessing or setting a property that isnt the key. So it seems there is a phantom entity in my datastore with key 3204258. THis entity doesn't really exist (queried the datastore from admin console) but for some reason its being returned by the query. Could my data store be in an inconsistent state? I've managed the following workaround by placing it as the first line in my for loop. Clearly an ugly hack: if (c.getOnTheCanId() == 3204258) { continue; } Any ideas?

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• JPA - Performance with using multiple entity manager

  - by Nguyen Tuan Linh

  My situation is: The code is not mine I have two kinds of database: one is Dad, one is Son. In Dad, I have a table to store JNDI name. I will look up Dad using JNDI, create entity manager, and retrieve this table. From these retrieved JNDI names, I will create multiple entity managers using multiple Son databases. The problem is: Son have thousands of entities. It takes each Son database around 10 minutes to load all entities. If there is 4 Son databases, it will be 40 minutes. My question: Is there any way to load all entities and use them for all entity manager? Please look at the code below For each Son JNDI: Map<String, String> puSonProperties = new HashMap<String, String>(); puSonProperties.put("javax.persistence.jtaDataSource", sonJndi); EntityManagerFactory emf = Persistence.createEntityManagerFactory("PUSon", puSonProperties); PUSon - All of them use the same persistence unit log.info("Verify entity manager for son: {0} - {1}", sonCode, emSon.find(Son_configuration.class, 0) != null ? "ok" : "failed!"); This is the actual code where the loading of all entities begins. 10 mins.

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• Entity Framework 4 / POCO - Where to start?

  - by Basiclife

  Hi, I've been programming for a while and have used LINQ-To-SQL and LINQ-To-Entities before (although when using entities it has been on a Entity/Table 1-1 relationship - ie not much different than L2SQL) I've been doing a lot of reading about Inversion of Control, Unit of Work, POCO and repository patterns and would like to use this methodology in my new applications. Where I'm struggling is finding a clear, concise beginners guide for EF4 which doesn't assume knowledge of EF1. The specific questions I need answered are: Code first / model first? Pros/cons in regards to EF4 (ie what happens if I do code first, change the code at a later date and need to regenerate my DB model - Does the data get preserved and transformed or dropped?) Assuming I'm going code-first (I'd like to see how EF4 converts that to a DB schema) how do I actually get started? Quite often I've seen articles with entity diagrams stating "So this is my entity model, now I'm going to ..." - Unfortunately, I'm unclear if they're created the model in the designer, saved it to generate code then stopped any further auto-code generation -or- They've coded (POCO)? classes and the somehow imported them into the deisgner view? I suppose what I really need is an understanding of where the "magic" comes from and how to add it myself if I'm not just generating an EF model directly from a DB. I'm aware the question is a little vague but I don't know what I don't know - So any input / correction / clarification appreciated. Needless to say, I don't expect anyone to sit here and teach me EF - I'd just like some good tutorials/forums/blogs/etc. for complete entity newbies Many thanks in advance

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• Going "behind Hibernate's back" to update foreign key values without an associated entity

  - by Alex Cruise

  Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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• Updating entity fields in app engine development server

  - by Joey

  I recently tried updating a field in one of my entities on the app engine local dev server via the sdk console. It appeared to have updated just fine (a simple float). However, when I followed up with a query on the entity, I received an exception: "Items in the mSomeList list must all be Key instances". mSomeList is just another list field I have in that entity, not the one I modified. Is there any reason manually changing a field would adversely throw something off such that the server gets confused? Is this a known bug? I wrote an http handler to alter the field through server code and it works fine if I take that approach. Update: (adding details) I am using the python google app engine server. Basically if I go into the Google App Engine Launcher and press the SDK Console button, then go into one of my entities and edit a field that is a float (i.e. change it from 0 to 3.5, for instance), I get the "Items in the mMyList list must all be Key instance" suddenly when I query the entity like this: query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() the RegionData entity is what has the mMyList member. As mentioned previously, if I do not manually change the field but rather do so through server code, i.e. query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() entry.mMyFloat = 3.5 entry.put() Then it works.

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• Using nHibernate to map two different data models to one entity model

  - by Dan

  I have two different data models that map to the same Car entity. I needed to create a second entity called ParkedCar, which is identical to Car (and therefore inherits from it) in order to stop nhibernate complaining that two mappings exists for the same entity. public class Car { protected Car() { IsParked = false; } public virtual int Id { get; set; } public bool IsParked { get; internal set; } } public class ParkedCar : Car { public ParkedCar() { IsParked = true; } //no additional properties to car, merely exists to support mapping and signify the car is parked } The only issue is that when I come to retrieve a Car from the database using the Criteria API like so: SessionProvider.OpenSession.Session.CreateCriteria<Car>() .Add(Restrictions.Eq("Id", 123)) .List<Car>(); The query brings back Car Entities that are from the ParkedCar data model. Its as if nhibernate defaults to the specialised entity. And the mappings are defiantly looking in the right place: <class name="Car" xmlns="urn:nhibernate-mapping-2.2" table="tblCar"> <class name="ParkedCar" xmlns="urn:nhibernate-mapping-2.2" table="tblParkedCar" > How do I stop this?

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• Doctrine 2 entity cannot be saved with its many-to-many related entities

  - by user1333185

  I'm writing a project in ZF and have many-to-many related accounts and videos entities and I provide the account with the videos collection. When I try to save the account I receive the following error: A new entity was found through the relationship 'Entities\Account#playlistVideos' that was not configured to cascade persist operations for entity: Entities\Video@000000004d5f02ef00000000196757dc. Explicitly persist the new entity or configure cascading persist operations on the relationship. If you cannot find out which entity causes the problem implement 'Entities\Video#__toString()' to get a clue. I found a suggested solution with cascade={"persist"} which should allow videos to be saved together with the account by only specifying $this-em-persist($account) but then I get the error: Fatal error: method_exists(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "Proxies\EntitiesAccountProxy" of the object you are trying to operate on was loaded before unserialize() gets called or provide a __autoload() function to load the class definition in... The same happens when I try to manually persist videos and account. Thank you for the help in advance.

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• Under what circumstances will an entity be able to lazily load its relationships in JPA

  - by Mowgli

  Assuming a Java EE container is being used with JPA persistence and JTA transaction management where EJB and WAR packages are inside a EAR package. Say an entity with lazy-load relationships has just been returned from a JPQL search, such as the getBoats method below: @Stateless public class BoatFacade implements BoatFacadeRemote, BoatFacadeLocal { @PersistenceContext(unitName = "boats") private EntityManager em; @Override public List<Boat> getBoats(Collection<Integer> boatIDs) { if(boatIDs.isEmpty()) { return Collections.<Boat>emptyList(); } Query query = em.createNamedQuery("getAllBoats"); query.setParameter("boatID", boatIDs); List<Boat> boats = query.getResultList(); return boats; } } The entity: @Entity @NamedQuery( name="getAllBoats", query="Select b from Boat b where b.id in : boatID") public class Boat { @Id private long id; @OneToOne(fetch=FetchType.LAZY) private Gun mainGun; public Gun getMainGun() { return mainGun; } } Where will its lazy-load relationships be loadable (assuming the same stateless request): Same JAR: A method in the same EJB A method in another EJB A method in a POJO in the same EJB JAR Same EAR, but outside EJB JAR: A method in a web tier managed bean. A method in a web tier POJO. Different EAR: A method in a different EAR which receives the entity through RMI. What is it that restricts the scope, for example: the JPA transaction, persistence context or JTA transaction?

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• Reattaching an object graph to an EntityContext: "cannot track multiple objects with the same key"

  - by dkr88

  Can EF really be this bad? Maybe... Let's say I have a fully loaded, disconnected object graph that looks like this: myReport = {Report} {ReportEdit {User: "JohnDoe"}} {ReportEdit {User: "JohnDoe"}} Basically a report with 2 edits that were done by the same user. And then I do this: EntityContext.Attach(myReport); InvalidOperationException: An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key. Why? Because the EF is trying to attach the {User: "JohnDoe"} entity TWICE. This will work: myReport = {Report} {ReportEdit {User: "JohnDoe"}} EntityContext.Attach(myReport); No problems here because the {User: "JohnDoe"} entity only appears in the object graph once. What's more, since you can't control how the EF attaches an entity, there is no way to stop it from attaching the entire object graph. So really if you want to reattach a complex entity that contains more than one reference to the same entity... well, good luck. At least that's how it looks to me. Any comments? UPDATE: Added sample code: // Load the report Report theReport; using (var context1 = new TestEntities()) { context1.Reports.MergeOption = MergeOption.NoTracking; theReport = (from r in context1.Reports.Include("ReportEdits.User") where r.Id == reportId select r).First(); } // theReport looks like this: // {Report[Id=1]} // {ReportEdit[Id=1] {User[Id=1,Name="John Doe"]} // {ReportEdit[Id=2] {User[Id=1,Name="John Doe"]} // Try to re-attach the report object graph using (var context2 = new TestEntities()) { context2.Attach(theReport); // InvalidOperationException }

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• Spring bean creation via deserialization

  - by mdma

  Spring has many different ways of creating beans, but is it possible to create a bean by deserializing a resource? My application has a number of Components, and each manipulates a certain type of data. During test, the data object is instantiated directly and set directly on the component, e.g. component.setData(someDataObject). At runtime, the data is available as a serialized object and read in from the serialized stream by the component. Rather than having each component explicitly deserialize it's data from the stream, it would be more consistent and flexible to have Spring deserialize the data object from a resource. Is there a DeserializerBeanFactory or something similar?

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• EntityFramework WCF issue

  - by Andres Blanco

  Right now i'm doing some tests involving entityFramework and WCF. As I understand, the EntityObjects generated are DataContracts and so, they can be serialized to the client. In my example I have a "Country" entity wich has 1 "Currency" as a property, when I get a Country and try to send it to the client, it throws an exception saying the data cant be written. But, the thing is, if I Get a Currency (which has a collection of Countries) and dont load its countries, it does work. The client gets all the entities. So, as a summary: - I have an entity with another entity as a property and cant be serialized. - I have another entity with an empty list of properties and it is successfully serialized. Any ideas on how to make it work?

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• Howw to add new value with generic Repository if there are foreign keys (EF-4)?

  - by Phsika

  i try to write a kind of generic repository to add method. Everything is ok to add but I have table which is related with two tables with FOREIGN KEY.But Not working because of foreign key public class DomainRepository<TModel> : IDomainRepository<TModel> where TModel : class { #region IDomainRepository<T> Members private ObjectContext _context; private IObjectSet<TModel> _objectSet; public DomainRepository() { } public DomainRepository(ObjectContext context) { _context = context; _objectSet = _context.CreateObjectSet<TModel>(); } //do something..... public TModel Add<TModel>(TModel entity) where TModel : IEntityWithKey { EntityKey key; object originalItem; key = _context.CreateEntityKey(entity.GetType().Name, entity); _context.AddObject(key.EntitySetName, entity); _context.SaveChanges(); return entity; } //do something..... } Calling REPOSITORY: //insert-update-delete public partial class AddtoTables { public table3 Add(int TaskId, int RefAircraftsId) { using (DomainRepository<table3> repTask = new DomainRepository<table3>(new TaskEntities())) { return repTask.Add<table3>(new table3() { TaskId = TaskId, TaskRefAircraftsID = RefAircraftsId }); } } } How to add a new value if this table includes foreign key relation

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• Is it possible that two requests at the same time double this code? (prevent double database entry)

  - by loostro

  1) The controller code (Symfony2 framework): $em = $this->getDoctrine()->getEntityManager(); // get latest toplist $last = $em->getRepository('RadioToplistBundle:Toplist')->findOneBy( array('number' => 'DESC') ); // get current year and week of the year $week = date('W'); $year = date('Y'); // if: // [case 1]: $last is null, meaning there are no toplists in the database // [case 2]: $last->getYear() or $last->getWeek() do not match current // year and week number, meaning that there are toplists in the // database, but not for current week // then: // create new toplist entity (for current week of current year) // else: // do nothing (return) if($last && $last->getYear() == $year && $last->getWeek() == $week) return; else { $new = new Toplist(); $new->setYear($year); $new->setWeek($week); $em->persist($new); $em->flush(); } This code is executed with each request to view toplist results (frontend) or list of toplists (backend). Anytime someone wants to access the toplist we first check if we should create a new toplist entity (for new week). 2) The question is: Is it possible that: User A goes to mydomain.com/toplist at 00:00:01 on Monday - the code should generate new entity the server slows down and it takes him 3 seconds to execute the code so new toplist entity is saved to database at 00:00:04 on Monday User B goes to mydomain.com/toplist at 00:00:02 on Monday at 00:00:02 there the toplist is not yet saved in database, thus UserB's request triggers the code to create another toplist entity And so.. after a few seconds we have 2 toplist entities for current week. Is this possible? How should I prevent this?

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• Many to many self join through junction table

  - by Peter

  I have an EF model that can self-reference through an intermediary class to define a parent/child relationship. I know how to do a pure many-to-many relationship using the Map command, but for some reason going through this intermediary class is causing problems with my mappings. The intermediary class provides additional properties for the relationship. See the classes, modelBinder logic and error below: public class Equipment { [Key] public int EquipmentId { get; set; } public virtual List<ChildRecord> Parents { get; set; } public virtual List<ChildRecord> Children { get; set; } } public class ChildRecord { [Key] public int ChildId { get; set; } [Required] public int Quantity { get; set; } [Required] public Equipment Parent { get; set; } [Required] public Equipment Child { get; set; } } I've tried building the mappings in both directions, though I only keep one set in at a time: modelBuilder.Entity<ChildRecord>() .HasRequired(x => x.Parent) .WithMany(x => x.Children ) .WillCascadeOnDelete(false); modelBuilder.Entity<ChildRecord>() .HasRequired(x => x.Child) .WithMany(x => x.Parents) .WillCascadeOnDelete(false); OR modelBuilder.Entity<Equipment>() .HasMany(x => x.Parents) .WithRequired(x => x.Child) .WillCascadeOnDelete(false); modelBuilder.Entity<Equipment>() .HasMany(x => x.Children) .WithRequired(x => x.Parent) .WillCascadeOnDelete(false); Regardless of which set I use, I get the error: The foreign key component 'Child' is not a declared property on type 'ChildRecord'. Verify that it has not been explicitly excluded from the model and that it is a valid primitive property. when I try do deploy my ef model to the database. If I build it without the modelBinder logic in place then I get two ID columns for Child and two ID columns for Parent in my ChildRecord table. This makes sense since it tries to auto create the navigation properties from Equipment and doesn't know that there are already properties in ChildRecord to fulfill this need. I tried using Data Annotations on the class, and no modelBuilder code, this failed with the same error as above: [Required] [ForeignKey("EquipmentId")] public Equipment Parent { get; set; } [Required] [ForeignKey("EquipmentId")] public Equipment Child { get; set; } AND [InverseProperty("Child")] public virtual List<ChildRecord> Parents { get; set; } [InverseProperty("Parent")] public virtual List<ChildRecord> Children { get; set; } I've looked at various other answers around the internet/SO, and the common difference seems to be that I am self joining where as all the answers I can find are for two different types. Entity Framework Code First Many to Many Setup For Existing Tables Many to many relationship with junction table in Entity Framework? Creating many to many junction table in Entity Framework

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• EntityFramework: using association or add property manualy

  - by dritterweg

  I'm starting to use Entity Framework. Let's say I have to Entity from my tables in DB. Here is the table schema Profiles ProfileId FirstName LastName Hobbies Id HobbyName OwnerId So one profile can have many hobbies. My Entity Framework: ProfileEntity ProfileId FirstName LastName Hobbies (collection of HobbyEntity) note: this created by the Association tool HobbyEntity Id HobbyName Owner (type of ProfileEntity) note: this created by the Association tool, for me this property is not important my question: should I use the "Association" tool to make the relationship between the two entities, which in result create a property of each entity (in ProfileEntity will create a HobbyEntity and vica versa) or should I not use the association and only add a scalar property manually such as List<HobbyEntity> in my ProfileEntity and OwnerId in HobbyEntity.

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• How to ORDER BY non-column field?

  - by Phil Bolduc

  I am trying to create an Entity SQL that is a union of two sub-queries. (SELECT VALUE DISTINCT ROW(e.ColumnA, e.ColumnB, 1 AS Rank) FROM Context.Entity AS E WHERE ...) UNION ALL (SELECT VALUE DISTINCT ROW(e.ColumnA, e.ColumnB, 2 AS Rank) FROM Context.Entity AS E WHERE ...) ORDER BY *??* LIMIT 50 I have tried: ORDER BY Rank and ORDER BY e.Rank but I keep getting: System.Data.EntitySqlException: The query syntax is not valid. Near keyword 'ORDER' I do not think it is a problem with the Rank column. I do think it is how I am trying to apply an order by to two different esql statements joined by union all. Could someone suggest: How to apply a ORDER BY to this kind of UNION/UNION ALL statment How to order by the non-entity column expression. Thanks.

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• We are using EntityFrame work in a singleton class ? - Not reflecting the DataBase changes in the fr

  - by anishmarokey

  Our application is using Entity Framework(.net 3.5) and single Ton . When i update in the back end through procedure.It is not reflecting in the entity context. I tried with refresh - But it is not refreshing Foreign Key. How to refresh the entire context in Entity Framework ?

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• Creating new Entities from Stored Procedure

  - by SK

  I have a stored procedure that retrieves existing rows from a table and also creates includes new rows that match the table definition and mapped entity (.net 3.5 entity framework). These new rows are not written to the database in the stored procedure. The stored procedure executes, but the new rows that were created will not load the navigation properties sucessfully i.e. the rows that do not actually exist in the database. e.g. database rows: key, data, FK 1, xxx, a 2, xxx, b returned rows from stored procedure: key, data, FK 1, xxx, a 2, xxx, b 3, yyy, a 4, yyy, b The entity will load FK entities a and b for rows 1 and 2, but for rows 3 and 4 the FK entity is null. Do I somehow need to add the new rows to the data context? or turn off tracking?

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• Adding Related Entities without using navigation properties

  - by Barisa Puter

  I have the following classes, set for testing: public class Company { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } public string Name { get; set; } } public class Employee { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int Id { get; set; } public string Name { get; set; } public int CompanyId { get; set; } public virtual Company Company { get; set; } } public class EFTestDbContext : DbContext { public DbSet<Employee> Employees { get; set; } public DbSet<Company> Companies { get; set; } } For the sake of testing, I wanted to insert one company and one employee for that company with single SaveChanges call, like this: Company company = new Company { Name = "Sample company" }; context.Companies.Add(company); // ** UNCOMMENTED FOR TEST 2 //Company company2 = new Company //{ // Name = "Some other company" //}; //context.Companies.Add(company2); Employee employee = new Employee { Name = "Hans", CompanyId = company.Id }; context.Employees.Add(employee); context.SaveChanges(); Even though I am not using navigational properties, but instead I've made relation over Id, this somehow mysteriously worked - employee was saved with proper foreign key to company which got updated from 0 to real value, which made me go ?!?! Some hidden C# feature? Then I've decided to add more code, which is commented in the snippet above, making it to be inserting of 2 x Company entity and 1 x Employee entity, and then I got exception: Unable to determine the principal end of the 'CodeLab.EFTest.Employee_Company' relationship. Multiple added entities may have the same primary key. Does this mean that in cases where foreign key is 0, and there is a single matching entity being inserted in same SaveChanges transaction, Entity Framework will assume that foreign key should be for that matching entity? In second test, when there are two entities matching the relation type, Entity Framework throws an exception as it is not able to figure out to which of the Companies Employee should be related to.

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• Why does my Spring Controller direct me to the wrong page?

  - by kc2001

  I am writing my first Spring 3.0.5 MVC app and am confused about why my controller mappings aren't doing what I expect. I have a VerifyPasswordController that is called after a user tries to log in by entering his name and password. // Called upon clicking "submit" from /login @RequestMapping(value = "/verifyPassword", method = RequestMethod.POST) @ModelAttribute("user") public String verifyPassword(User user, BindingResult result) { String email = user.getEmail(); String nextPage = CHOOSE_OPERATION_PAGE; // success case if (result.hasErrors()) { nextPage = LOGIN_PAGE; } else if (!passwordMatches(email, user.getPassword())) { nextPage = LOGIN_FAILURE_PAGE; } else { // success } return nextPage; } I can verify in the debugger that this method is being called, but afterwards, the verifyPassword page is displayed rather than the chooseOperation page. The console output of WebLogic seems to show that my mapping are correct: INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation.*] onto handler 'chooseOperationController' INFO : org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping - Mapped URL path [/chooseOperation/] onto handler 'chooseOperationController' Here is the ChooseOperationController: @Controller @SessionAttributes("leaveRequestForm") public class ChooseOperationController implements PageIfc, AttributeIfc { @RequestMapping(value = "/chooseOperation") @ModelAttribute("leaveRequestForm") public LeaveRequest setUpLeaveRequestForm( @RequestParam(NAME_ATTRIBUTE) String name) { LeaveRequest form = populateFormFromDatabase(name); return form; } // helper methods omited } I welcome any advice, particularly "generic" techniques for debugging such mapping problems. BTW, I've also tried to "redirect" to the desired page, but got the same result. servlet-context.xml: <?xml version="1.0" encoding="UTF-8"?> <beans:beans xmlns="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation=" http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure --> <!-- Enables the Spring MVC @Controller programming model --> <annotation-driven /> <!-- Handles HTTP GET requests for /resources/** by efficiently serving up static resources in the ${webappRoot}/resources directory --> <resources mapping="/resources/**" location="/resources/" /> <!-- Resolves views selected for rendering by @Controllers to .jsp resources in the /WEB-INF/views directory --> <beans:bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <beans:property name="prefix" value="/WEB-INF/views/" /> <beans:property name="suffix" value=".jsp" /> </beans:bean> <context:component-scan base-package="com.engilitycorp.leavetracker" /> <beans:bean id="leaveRequestForm" class="com.engilitycorp.leavetracker.model.LeaveRequest" /> </beans:beans> The constants: String LOGIN_FAILURE_PAGE = "loginFailure"; String LOGIN_PAGE = "login"; String CHOOSE_OPERATION_PAGE = "chooseOperation";

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