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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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• select lastest 2 element group by a topic_id

  - by Luca Romagnoli

  Hi i have to select the 2 lastest element for every topic ex: table: msg id | topic_id ----------- 1 | 1 2 | 1 3 | 1 4 | 1 5 | 2 6 | 2 7 | 2 8 | 3 i want obtain these rows: 3 1 4 1 6 2 7 2 8 3 How can i do? thanks

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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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• 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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• Group by with ActiveRecord in Rails

  - by Adnan

  Hello, I have a the following table with rows: ================================================================ id | name | group1 | group2 | group3 | group4 | ================================================================ 1 | Bob | 1 | 0 | 0 | 1| ================================================================ 2 | Eric| 0 | 1 | 0 | 1| ================================================================ 3 | Muris | 1 | 0 | 1 | 1| ================================================================ 4 | Angela | 0 | 0 | 0 | 1| ================================================================ What would be the most efficient way to get the list with ActiveRecords ordered by groups and show their count like this: group1 (2) group2 (1) group3 (1) group4 (4) All help is appreciated.

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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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• 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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• html entity is not rendered

  - by Michael

  If I just put in XUL file <label value="&#176;C"/> it works fine. However, I need to assing &#176; value to that label element and it doesn't show degree symbol, instead literal value.

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• GROUP BY on multiple columns

  - by Tams

  I have a table that looks like the following - Id Reference DateAttribute1 DateAttribute2 1 MMM005 2011-09-11 2012-09-10 2 MMM005 2012-06-13 2012-09-10 3 MMM006 2012-08-22 2012-09-10 4 MMM006 2012-08-22 2012-09-11 I have handle to the id values. I would like to query such that I get the following result Id Reference DateAttribute1 DateAttribute2 2 MMM005 2012-06-13 2012-09-10 4 MMM006 2012-08-22 2012-09-11 I would like my result to be grouped by reference and then 'DateAttribute1' and then 'DateAttribute2' as such - DateAttribute1 has a priority over DateAttribute2 as you can see above in the result. How should I write my query to fetch the results in the above manner? Any solution?

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• how to select specific number of child entities instead of all in entity framework 3.5?

  - by Sasha

  Hi all, i am wondering how can i select specific number of child objects instead of taking them all with include? lets say i have object 'Group' and i need to select last ten students that joined the group. When i use '.Include("Students"), EF includes all students. I was trying to use Take(10), but i am pretty new to EF and programming as well, so i couldn't figure it out. Any suggestions? UPDATED: ok, i have Group object already retrieved from db like this: Group group = db.Groups.FirstOrDefault(x=>x.GroupId == id) I know that i can add Include("Students") statement, but that would bring ALL students, and their number could be quite big whether i need only freshest 10 students. Can i do something like this: var groupWithStudents = group.Students.OrderByDescending(//...).Take(10);? The problem with this is that Take< no longer appears in intellisense. Is this clear enough? Thanks for responses

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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 comments are removed upon saving of updated model

  - by Adam Asham

  In my entities, I tend to add comments for the properties but as I update the model and save it, all the comments are removed. How can I stop this behavior?

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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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• 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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• Group mysql query by 15 min intervals

  - by gsiener

  I've got a monitoring system that is collecting data every n seconds (n ~=10 but varies). I'd like to aggregate the collected data by 15 minute intervals. Is there a way to corral the timestamp column into 15 minute chunks to allow for grouping to work?

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• How to retrieve base class only (entity framework)?

  - by Juvaly

  Hi All, I've been scratching my head here for a while now... I have a Consumer class and a BillableConsumer class that inherits Consumer. They are both a part of the Consumers set. The problem is that this following query: Consumer consumer = (from c in _ctx.Consumers where c.ID = id select c).First(); returns a BillableConsumer instance! Just the same as this query: BillableConsumer bconsumer = (from c in _ctx.Consumers.OfType<BillableConsumer>() where c.ID = id select c).First(); How can I return an instance of just the base class? (these are separate tables in the data store).

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• Entity Framework 4 and 0:1, 0:1 relationships

  - by Eric J.

  I'm using the Model First approach with EF 4 and hit a snag with two tables, Participant (singular because pre-existing from another app) and ActiveParticipants. A Participant may or may not be associated with exactly one ActiveParticipant and vice versa. When I create an association, everything seems to go well on the surface, but then I get a runtime error complaining that Participant does not contain the column ActiveParticipant_Id. It does contain a column ActiveParticipantId (no underscore). When I view the diagram as XML, there's a line like this: <Property Name="ActiveParticipant_Id" Type="uniqueidentifier" Nullable="true" /> Why is it adding an underscore? Is there anything special I need to do for 0:1, 0:1 relationships?

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• Left Join with Entity Framework

  - by sanfra1983

  hi, someone can tell me how to do this query in EF1: select a.idAnimali, a.titolo, a.commenti, a.ordine, a.idcatanimali, table1.nomefoto FROM tabanimali as a LEFT JOIN (SELECT idanimali, nomefoto tabfotoanimali FROM LIMIT 1) AS Table1 On a.idAnimali = table1.idanimali WHERE a.idcatanimali = idcatanimale Thanks

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• What is the difference between these two statements (asp.net/c#/entity framework)

  - by user318573

  IEnumerable<Department> myQuery = (from D in myContext.Departments orderby D.DeptName select D); var myQuery = (from D in myContext.Departments orderby D.DeptName select D); What is the difference between these two statements above? In my little asp.net/C#/ EF4.0 app I can write them either way, and as far as how I want to use them, they both work, but there has to be a reason why I would choose one over the other?

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• Does Entity Framework saves related classes automatically?

  - by herbatnic

  Let's assume that we have such classes public class A{ string someField { get; set; } public virtual B B {get; set; } } public class B { int someIntField {get; set; } [ForeignKey("Id")] [Required] public virtual A A { get; set; } } In code I create new instances for both of them and making relation like: A a = new A () { someField = "abcd"}; B b = new B () { someIntField = 42 }; A.B = b; B.A = a; Should I using DBContext to save both classes like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.Bs.Add(B); myDBContext.SaveChanges(); } Or saving it like that: using (var db = new myDbContext()) { myDbContext.As.Add(A); myDbContext.SaveChanges(); } is enough to store related objects into database?

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• multiple join query in entity framework

  - by gvLearner

  I have following tables tasks id | name | proj_id 1 | task1 | 1 2 | task2 | 1 3 | task3 | 1 projects id | name 1 | sample proj1 2 | demo project budget_versions id | version_name| proj_id 1 | 50 | 1 budgets id | cost | budget_version_id | task_id 1 | 3000 | 1 | 2 2 | 5000 | 1 | 1 I need to join these tables to get a result as below task_id | task_name | project_id | budget_version | budget_id | cost 1 | task1 | 1 | 1 | 2 |5000 2 | task2 | 1 | 1 | 1 |3000 3 | task3 | 1 | NULL | NULL |NULL select tsk.id,tsk.name, tsk.project_id, bgtver.id, bgt.id, bgt.cost from TASK tsk left outer join BUDGET_VERSIONS bgtver on tsk.project_id= bgtver.project_id left outer join BUDGETS bgt on bgtver.id = bgt.budget_version_id and tsk.id = bgt.task_id where bgtver.id = 1

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• how to group MySql rows based on month?

  - by understack

  I've a table with a datetime (format: 'Y-m-d H:i:s') 'created' field and 'amount' (integer) field in each row. Now I want to find out total 'amount' in last year month wise. How can I do this? EDIT I made an edit to clarify the actual problem.

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• Argument exception after trying to use TryGetObjectByKey

  - by Rickjaah

  Hi, EDIT: Somethings wrong.... I have to use objectContext.Frontpages.ToArray() before I can use TryGetObjectByEntityKey(). Any ideas anyone? I'm trying to retrieve an object from my database using entity (framework 4) When I use the following code it gives an ArgumentException: An item with the same key has already been added. if (databaseContext.TryGetObjectByKey(entityKey, out result)) { return (result != null && result is TEntityObject) ? result as TEntityObject : null; } else { return null; } When I check the objectContext, I see the entities, but only if I enumerate the specific list of entities manually using VS2010, it works. What am I missing? Do I have to do something else before i can get the item from the database? I searched google, but could not find any results, the same for the msdn library EDIT: Still working on this.... It's a weird problem. I retrieve a value, but get an error that says a duplicate item exists. STACKTRACE: [ArgumentException: An item with the same key has already been added.] System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +52 System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) +9549131 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.LoadRelationshipTypes() +661 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.LoadTypesFromAssembly() +17 System.Data.Metadata.Edm.ObjectItemAssemblyLoader.Load() +25 System.Data.Metadata.Edm.ObjectItemAttributeAssemblyLoader.Load() +4 System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, ObjectItemLoadingSessionData loadingData) +160 System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, KnownAssembliesSet knownAssemblies, EdmItemCollection edmItemCollection, Action1 logLoadMessage, Object& loaderCookie, Dictionary2& typesInLoading, List1& errors) +166 System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies, EdmItemCollection edmItemCollection, Action`1 logLoadMessage) +316 System.Data.Metadata.Edm.MetadataWorkspace.ImplicitLoadAssemblyForType(Type type, Assembly callingAssembly) +306 System.Data.Metadata.Edm.MetadataWorkspace.ImplicitLoadFromEntityType(EntityType type, Assembly callingAssembly) +109 System.Data.Objects.ObjectContext.TryGetObjectByKey(EntityKey key, Object& value) +288 EDIT: Lazy loading is set to true. EDIT: Somethings wrong.... I have to use objectContext.Frontpages.ToArray() before I can use TryGetObjectByEntityKey(). Any ideas anyone?

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• Best practice for structuring a new large ASP.NET MVC2 plus EF4 VS2010 solution?

  - by Nick

  Hi, we are building a new web application using Microsoft ASP.NET MVC2 and Entity Framework 4. Although I am sure there is not one right answer to my question, we are struggling to agree a VS2010 solution structure. The application will use SQL Server 2008 with a possible future Azure cloud version. We are using EF4 with T4 POCOs (model-first) and accessing a number of third-party web-services. We will also be connecting to a number of external messaging systems. UI is based on standard ASP.NET (MVC) with jQuery. In future we may deliver a Silverlight/WPF version - as well as mobile. So put simply, we start with a VS2010 blank solution - then what? I have suggested 4 folders Data (the EF edmx file etc), Domain (entities, repositories), Services (web-services access), Presentation (web ui etc). However under Presentation, creating the ASP.NET MVC2 project obviously creates it's own Models folder etc and it just doesn't seem to fit too well in this proposed structure. I'm also missing a business layer (or does this sit in the domain?). Again I am sure there is no one right way to do it, but I'd really appreciate your views on this. Thanks

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