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  • entity framework navigation property further filter without loading into memory

    - by cellik
    Hi, I've two entities with 1 to N relation in between. Let's say Books and Pages. Book has a navigation property as Pages. Book has BookId as an identifier and Page has an auto generated id and a scalar property named PageNo. LazyLoading is set to true. I've generated this using VS2010 & .net 4.0 and created a database from that. In the partial class of Book, I need a GetPage function like below public Page GetPage(int PageNumber) { //checking whether it exist etc are not included for simplicity return Pages.Where(p=>p.PageNo==PageNumber).First(); } This works. However, since Pages property in the Book is an EntityCollection it has to load all Pages of a book in memory in order to get the one page (this slows down the app when this function is hit for the first time for a given book). i.e. Framework does not merge the queries and run them at once. It loads the Pages in memory and then uses LINQ to objects to do the second part To overcome this I've changed the code as follows public Page GetPage(int PageNumber) { MyContainer container = new MyContainer(); return container.Pages.Where(p=>p.PageNo==PageNumber && p.Book.BookId==BookId).First(); } This works considerably faster however it doesn't take into account the pages that have not been serialized to the db. So, both options has its cons. Is there any trick in the framework to overcome this situation. This must be a common scenario where you don't want all of the objects of a Navigation property loaded in memory when you don't need them.

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  • How to create relationship mapping via Entity framework

    - by James
    I have following domain model: User { int Id; } City { int Id; } UserCity { int UserId, int CityId, dateTime StartDate } In the function where I have to attach a user to a city, the following code is working for me: UserCity uc = new UserCity(); //This is a db hit uc.User = MyEntityFrameworkDBContext.User.FirstOrDefault(u => u.ID == currentUserId); //this is a db hit uc.City = MyEntityFrameworkDBContext.City.FirstOrDefault(c => c.ID == currentCityId); uc.StartDate = userCityStartDate; //this is a db hit MyEntityFrameworkDBContext.SaveChanges(); Is there any way I can create relationships with just one single DB hit? The first two db hits are not required, actually.

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  • Doctrine: How to traverse from an entity to another 'linked' entity?

    - by ropstah
    I'm loading 3 different tables using a cross-join in Doctrine_RawSql. This brings me back the following object: User -> User class (doctrine base class) Settings -> DoctrineCollection of Setting User_Settings -> DoctrineCollection of User_Setting The object above is the result of a many-to-many relationship between User and Setting where User_Setting acts as a reference table. User_Setting also contains another field named value. This obviously contains the value of the corresponding Setting. All good so far, however the Settings and User_Settings properties of the returned User object are in no way linked to each other (apart from the setting_id field ofcourse). Is there any direct way to traverse directly from the Settings property to the corresponding User_Settings property? This is the corresponding query: $sets = new Doctrine_RawSql(); $sets->select('{us.*}, {s.*}, {uset.*}') ->from('(User us CROSS JOIN Setting s) LEFT JOIN User_Setting uset ON us.user_id = uset.user_id AND s.setting_id = uset.setting_id') ->addComponent('us', 'User us') ->addComponent('uset', 'us.User_Setting uset') ->addComponent('s', 'us.Setting s') ->where('s.category_id = ? AND us.usr_auto_key = ?',array(1, 1)); $sets = $sets->execute();

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  • Entity framework with Linq to Entities performance

    - by mare
    If I have a static method like this public static string GetTicClassificationTitle(string classI, string classII, string classIII) { using (TicDatabaseEntities ticdb = new TicDatabaseEntities()) { var result = from classes in ticdb.Classifications where classes.ClassI == classI where classes.ClassII == classII where classes.ClassIII == classIII select classes.Description; return result.FirstOrDefault(); } } and use this method in various places in foreach loops or just plain calling it numerous times, does it create and open new connection every time? If so, how can I tackle this? Should I cache the results somewhere, like in this case, I would cache the entire Classifications table in Memory Cache? And then do queries vs this cached object? Or should I make TicDatabaseEntities variable static and initialize it at class level? Should my class be static if it contains only static methods? Because right now it is not.. Also I've noticed that if I return result.First() instead of FirstOrDefault() and the query does not find a match, it will issue an exception (with FirstOrDefault() there is no exception, it returns null). Thank you for clarification.

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  • Entity framework 4 add to many-to-many

    - by mehanik
    I have model whith 3 tabels and one is link table with additional field: Groups Id Name Users Id Name Roles Id Name LinkTable Id GroupId UserId RoleId The quuestion is how to add 3 related entities: Code bellow doesn't work. using (var db = new dbEntities()) { db.Groups.AddObject(Group.CreateGroup(1, "TestGroup")); db.Users.AddObject(User.CreateUser(1, "AdminUser")); db.Roles.AddObject(Role.CreateRole(1, "Admin")); db.UserGroupRoles.AddObject(UserGroupRole.CreateUserGroupRole(1, 1, 1, 1)); db.SaveChanges(); }

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  • ado.net data entity problem

    - by ognjenb
    I have this error Cannot implicitly convert type 'System.Linq.IQueryable' to 'Mvc.Models.engineer'. An explicit conversion exists (are you missing a cast?) after write this code engineer Ing = new engineer(); Ing = from j in testPersons.ibekoengineer select j.Name; What is wrong?

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  • Entity framework 4.0 compiled query with Where() clause issue

    - by Andrey Salnikov
    Hello, I encountered with some strange behavior of System.Data.Objects.CompiledQuery.Compile function - here is my code for compile simple query: private static readonly Func<DataContext, long, Product> productQuery = CompiledQuery.Compile((DataContext ctx, long id) => ctx.Entities.OfType<Data.Product>().Where(p => p.Id == id) .Select(p=>new Product{Id = p.Id}).SingleOrDefault()); where DataContext inherited from ObjectContext and Product is a projection of POCO Data.Product class. My data context in first run contains Data.Product {Id == 1L} and in second Data.Product {Id == 2L}. First using of compilled query productQuery(dataContext, 1L) works perfect - in result I have Product {Id == 1L} but second run productQuery(dataContext, 2L) always returns null, instead of context in second run contains single product with id == 2L. If I remove Where clause I will get correct product (with id == 2L). It seems that first id value caching while first run of productQuery, and therefore all further calls valid only when dataContext contains Data.Product {id==1L}. This issue can't be reproduced if I've used direct query instead of its precompiled version. Also, all tests I've performed on test mdf base using SQL Server 2008 express and Visual studio 2010 final from my ASP.net application.

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  • Unable to delete inherited entity class in EF4

    - by Coding Gorilla
    I have two entities in an EF4 model (using Model First), let's call them EntityA and EntityB. EntityA is marked as abstract, and EntityB inherits from EntityA. They are similar to the following: public class EntityA { public Guid Id; public string Name; public string Uri; } public class EntityB : EntityA { public string AnotherProperty; } The generated database tables look as I would expect them, with EntityA as on table, and then another table like: EntityA_EntityB Id (PK, FK, uniqueidentifier) AnotherProperty (varchar) There is a foreign key constraint on EntityA_EntityB that references EntityA's Id property, no cascades are configured (although I did try changing these myself). The problem is that when I attempt to do something like: Context.DeleteObject(EntityA_EntityB); EF attempts to delete the EntityA_EntityB table record before deleting the EntityA table record, which of course violates the foreign key constraint on EntityA_EntityB table. Using EFProfiler I see the following commands being sent to the database: delete [dbo].[EntityA_EntityB] where (([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) followed by delete [dbo].[EntityA] where ([Id] = '5c02899f-09ea-2ed9-d44b-01aef80f6b64' /* @0 */) I'm completely stumped as to how to get around this problem. I would think the EF should know that it needs to delete the base class first, before deleting the inherited class. I know I could do some triggers or other database type solutions, but I'd rather avoid doing that if I can. All my classes are POCO built using some customized T4 templates. I don't want to paste in a lot of extraneous code, but if you need more information I'll provide what I can.

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  • Merge Function In Entity FrameWork?

    - by Ahmed
    In NHibernate there is a merge function that does the following: if there is a persistent instance with the same identifier currently associated with the session, copy the state of the given object onto the persistent instance if there is no persistent instance currently associated with the session, try to load it from the database, or create a new persistent instance the persistent instance is returned Is this possible in EF? I mean this part : copy the state of the given object onto the persistent instance. And if i used ApplyCurrentValues it seemes to be as update behavior or not?

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  • Replace Entity Framework object

    - by majkinetor
    In MVC app, I am having this big object that is used in classic view/edit/create pattern. When user edits the object I save it as: public bool SetMyObject(MyObject newObject) { MyObject current = GetObjectById(newObject.Id); current.Prop1 = newObject.Prop1 ... current.PropN = newObject.PropN db.SaveChanges(); } MyObject is pretty big so I am wondering is there any better way to do this, not involving per-property assignments. For instance something along the lines db.MyObject.UpdateObject(current, tnew). Ty.

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  • Query Entity Framework 4

    - by nick
    Hi, Is it possible to run a query on an EF4.0 data context and get all objects of a certain type? Say the context has books, genres & authors but I only have a generic parameter, t. Is it possible to get all of type just by using this t? I don't think it is :(

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  • Entity Framework 4 omits some associations during model generation

    - by kzen
    After creating an EF4 model from a SQL Server database I noticed that all the relationships of my Users table were not imported into the model as associations. All the other relationships were imported fine. My Users table has a PK userId which is a char(7) field and it is integrated into several other tables in the database as an FK but for some reason EF4 does not import these relationships as associations during the model generation process... Does anyone have any ideas why this would be happening?

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  • Entity Framework Create Database & Tables At Runtime

    - by dhsto
    I created some tables in an .edmx file and have been generating the database by selecting "Generate Database From Model" and manually executing an .edmx.sql file on the database to build the tables. Now, however, I am creating a setup dialog that allows the user to connect the program up to their own database. I thought running context.CreateDatabase would be good enough to create the database, along with the tables, but the tables are not created. What is the preferred method for creating the database and tables when the user specifies their own server and database to use, when originally starting with a model?

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  • SQL database self interaction entity

    - by Ricardo Costa
    I've been working on a database, wich is referent to an Aeroport management. I'm having a problem that it's freaking me out.. What i'm trying to do is, assuming that a client wants to know the distance between 2 locations, in miles or kms. As an example, if the user wants to know the distance between London and Amsterdam, should that distance be calculated by a formule or should it be already stored on the database? (1,N) ____________ ____________|__ | | | | | City/Airport |<---------| |______________| How can i show to user the distance between his 2 choices? RicardoCosta

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  • Delete database. Entity Framework

    - by Idotz
    I have a very annoying issue and I would love a solution. The problem: I followed the MDSN tutorial- http://www.asp.net/mvc/tutorials/mvc-4/getting-started-with-aspnet-mvc4/adding-a-model Then I tried this guide according to my needs and I set up a database GAMES.MDF.   Then, I deleted the database and set it up again, is supposedly work (I can write and read data), but There is no such database in the APP_DATA folder. Like it keeps it somewhere in my PC and reuse it.   I even tried a new project and it did not work, works but not in the library, and it even uses the data I created before. I even deleted the DB from SQL Server Management Studio 2008. Does anyone know what the hell? How do I delete it permanently, not to remain any trace of him?   Thank you.  Ido

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  • Why use Entity Framework over Linq2SQL if...

    - by Refracted Paladin
    To be clear, I am not asking for a side by side comparision which has already been asked Ad Nauseum here on SO. I am also Not asking if Linq2Sql is dead as I don't care. What I am asking is this.... I am building internal apps only for a non-profit organization. I am the only developer on staff. We ALWAYS use SQL Server as our Database backend. I design and build the Databases as well. I have used L2S successfully a couple of times already. Taking all this into consideration can someone offer me a compelling reason that I should use EF instead of L2S? I was at Code Camp this weekend and after an hour long demonstration on EF, all of which I could have done in L2S, I asked this same question. The speakers answer was, "L2S is dead..." Very well then! NOT! (see here) I understand EF is what MS WANTS us to use in the future(see here) and that it offers many more customization options. What I can't figure out is if any of that should, or does, matter for me in this environment. One particular issue we have here is that I inherited the Core App which was built on 4 different SQL Data bases. L2S has great difficulty with this but when I asked the aforementioned speaker if EF would help me in this regard he said "No!"

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  • Entity Framework: Attached Entities not Saving

    - by blog
    Hello: I can't figure out why calling SaveChanges() on the following code results in no changes to the objects I attached: // delete existing user roles before re-attaching if (accountUser.AccountRoles.Count > 0) { foreach (AccountRole role in accountUser.AccountRoles.ToList()) { accountUser.AccountRoles.Remove(role); } } // get roles to add List<int> roleIDs = new List<int>(); foreach (UserRole r in this.AccountRoles) { roleIDs.Add(r.RoleID); } var roleEntities = from roles in db.AccountRoles where roleIDs.Contains(roles.id) select roles; accountUser.AccountRoles.Attach(roleEntities); db.SaveChanges(); In the debugger, I see that the correct roleEntities are being loaded, and that they are valid objects. However, if I use SQL Profiler I see no UPDATE or INSERT queries coming in, and as a result none of my attached objects are being saved.

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  • Entity Framework with SQL Server 2000 (APPLY Operator) issue

    - by How Lun
    Hello, I have a simple Linq query below: var seq = (from n in GetObjects() select n.SomeKey) .Distinct() .Count(); This query works find with SQL Server 2005 and above. But, this start to give headache when I hooked the EF to SQL Server 2000. Because EF is using APPLY operator which only SQL Server 2005 and above can be supported. I do not know why the hell EF is using APPLy operator instead of sub queries. My current work around is: var seq = (from n in GetObjects() select n.SomeKey) .Distinct() .ToList() .Count(); But, I can forsee more problems to come. The above query is just a simple one. Did anyone come across such issue? And how you guys work around it? Or is there a way to force EF not to use APPLY operator? Any help will be very much appreciated. How Lun.

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  • Entity framework Update fails when object is linked to a missing child

    - by McKay
    I’m having trouble updating an objects child when the object has a reference to a nonexising child record. eg. Tables Car and CarColor have a relationship. Car.CarColorId CarColor.CarColorId If I load the car with its color record like so this var result = from x in database.Car.Include("CarColor") where x.CarId = 5 select x; I'll get back the Car object and it’s Color object. Now suppose that some time ago a CarColor had been deleted but the Car record in question still contains the CarColorId value. So when I run the query the Color object is null because the CarColor record didn’t exist. My problem here is that when I attach another Color object that does exist I get a Store update, insert error when saving. Car.Color = newColor Database.SaveChanges(); It’s like the context is trying to delete the nonexisting color. How can I get around this?

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  • Saving a modified object from ASP.NET MVC View Using Entity-Franework 4

    - by Dani
    I retrieve an object graph from DB using EF4. The context is closed as soon as the data retrieve and the data passes to the controller, and then to the view. in the view the data is modified, and then the controller gets it back. From the controller I run Repository.Update(MyEmp); and in my repository the code goes: using (var context = new mydb()) { if (myEmp.ID != 0) // Checking if it's modified or new { context.Emp.Attach(MyEmp); int result = context.SaveChanges(); return myEmp.ID; } } The problem - once attached, the object entityState goes to unchanged, and not modified, and of course - nothing is saved to the database. What am I doing wrong ?

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