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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Created nested model setting a property on nested model before save

    - by CWitty
    I have two models a Company and a User the Company has_many :users and the User belongs_to :company. I have a form such as: <%= form_for @company, data: {toggle: :validator}, novalidate: "novalidate", html: {role: :form} do |f| %> company fields Then in there I have <%= f.fields_for :users, @company.users.build do |user_form| %> A bunch of user fields It posts the data with the nested attributes of users_attributes: {"0" => {name: "Chad"}} But it doesn't create the user only the company object. Company Model class Company < ActiveRecord::Base has_many :users, dependent: :destroy has_many :contacts, dependent: :destroy accepts_nested_attributes_for :users accepts_nested_attributes_for :contacts attr_accessor :card_token, :users_attributes before_create :create_company_customer_token before_create :create_admin_user before_destroy :set_deleted_flag validates_presence_of :name, :phone_number private def create_admin_user self.users.first.admin = true end def set_deleted_flag self.deleted = true save users.each do |u| u.destroy end false end def create_company_customer_token begin customer = Stripe::Customer.create(description: "Company: #{self.name}", card: self.card_token, plan: self.plan) self.stripe_customer_id = customer['id'] rescue Stripe::StripeError => e self.errors.add(:stripe_customer_id, "Looks like we are having an issue at the moment, please try again shortly") @logger ||= Rails.logger @logger.error(e) end end end User Model class User < ActiveRecord::Base include Clearance::User has_many :messages belongs_to :company before_destroy :set_deleted_flag after_create :send_welcome_email validates_presence_of :first_name, :last_name validates_uniqueness_of :email, scope: :company_id, conditions: -> { where.not(deleted: true) } def name "#{first_name} #{last_name}" end private def set_deleted_flag self.deleted = true save end def send_welcome_email UserMailer.welcome_email(self).deliver end end

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  • Mapping composite foreign keys in a many-many relationship, with overlapping components.

    - by Kirk Broadhurst
    I have a Page table and a View table. There is a many-many relationship between these two via a PageView table. Unfortunately all of these tables need to have composite keys (for business reasons). Page has a primary key of (PageCode, Version), View has a primary key of (ViewCode, Version). PageView obviously enough has PageCode, ViewCode, and Version. The FK to Page is (PageCode, Version) and the FK to View is (ViewCode, Version) Makes sense and works, but when I try to map this in Entity framework I get Error 3021: Problem in mapping fragments...: Each of the following columns in table PageView is mapped to multiple conceptual side properties: PageView.Version is mapped to (PageView_Association.View.Version, PageView_Association.Page.Version) So clearly enough, EF is having a complain about the Version column being a common component of the two foreign keys. Obviously I could create a PageVersion and ViewVersion column in the join table, but that kind of defeats the point of the constraint, i.e. the Page and View must have the same Version value. Has anyone encountered this, and is there anything I can do get around it? Thanks!

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  • Review: ComponentOne Studio for Entity Framework

    - by Tim Murphy
    While I have always been a fan of libraries that improve coding efficiency and reduce code redundancy I have mostly been using ones that were in the public domain.  As part of the Geeks With Blogs Influencers program a got my hands on ComponentOne’s Studio for Entity Framework.  Below are my thought after working with the product for several weeks. My coding preference has always been maintainable code that is reusable across an enterprises protfolio.  Because of this my focus in reviewing this product is less on the RAD components and more on its benefits for layered applications using code first Entity Framework. Before we get into the pros and cons here is a summary of the main feature listed for SEF. Unified Data Context Virtual Data Access More Powerful Data Binding Pros The first thing that I found to my liking is the C1DataSource. It basically manages a cache for your Entity Model context.  Under RAD conditions this is setup automatically when you drop the object on a your design surface.  If you are like me and want to abstract you data management into a library it takes a little more work, but it is still acceptable and gains the same benefits. The second feature that I found beneficial is the definition of views with improved sorting and filtering.  Again the ease of use of these features is greater on the RAD side but no capabilities are missing when manipulating object in code. Linq has become my friend over the last couple of years and it was great to see that ComponentOne had ensured that it remained a first class citizen in their design.  When you look into this product yourself I would suggest taking a dive into LiveLinq which allow the joining of different data source types. As I went through discovering the features of this framework I appreciated the number of examples that they supplied for different uses.  Besides showing how to use SEF with WinForms, WPF and Silverlight they also showed how to accomplish tasks both RAD, code only and MVVM approaches. Cons The only area that I would really like to see improvement is in there level of detail in their documentation.  Specifically I would like to have seen some of the supporting code explained, such as what some supporting object did, in the examples instead of having to go to the programmer’s reference. I did find some times where currently existing projects had some trouble determining scope that the RAD controls were allowed, but I expect this is something that is in part end user related. Summary Overall I found the Studio for Entity Framework capable and well thought out.  If you are already using the Entity Framework this product will fit into your environment with little effort in return for greater flexibility and greater robustness in your solutions. Whether the $895 list price for a standard version works for you will depend on your return on investment. Smaller companies with only a small number of projects may not be able to stomach it, you get a full featured product that is supported by a well established company.  The more projects and the more code you have the greater your return on investment will be. Personally I intend to apply this product to some production systems and will probably have some tips and tricks in the future. del.icio.us Tags: ComponentOne,Studio for Entity Framework,Geeks With Blogs,Influencers,Product Reviews

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  • ASP.NET MVC in Action: The model in depth

    In this chapter, we’ll explore a model for a system that helps to manage a small conference, like a Code Camp. The model enables the application to provide an interesting service. Without the model, the application provides no value. We place great importance on creating a rich model with which our controllers can work. Presented By: NEC   Ads by Pheedo

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  • Introducing the Entity Framework

    The Entity Framework provides a .NET class-based model of a data store, letting you query the model with LINQ, while the model do the background grunt work of contacting the data store to add, update, or delete data.

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  • Rotate model using quaternion

    - by ChocoMan
    Currently I have this to rotate my 3D model that rotates on it's local axis independent from the world's axis: // Rotate model with Right Thumbstick modelRotation -= pController.ThumbSticks.Right.X * mRotSpeed; // float value What I'm trying to do is rotate the model using quaternion and not by a matrix. I've searched for tutorials, but have found none that explains thoroughly on how to achieve this. Does anyone know how to I can use quaternions to rotate my model or a complete tutorial?

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  • Understanding the SQL Server 2012 BI Semantic Model (BISM)

    SQL Server 2012 introduced an unified BI Semantic Model (BISM) which is based on some of the existing as well as some new technologies. This model is intended to serve as one model for all end user experiences for reporting, analytics, scorecards, dashboards, etc. In this tip, I will talk in detail about the new BISM, how it differs from earlier the earlier Unified Dimensional Model (UDM) and how BISM lays down a foundation for future.

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  • Create a many to many relationship in Entity Framework skipping extra data in the link table.

    - by Paul Smith
    I would like to model the following many to many relationship. Table A ID Field1 Field2 Table B ID Field1 Field2 LinkTable A_ID B_ID Field_I_want_to_ignore As I understand it, if LinkTable.Field_I_want_to_ignore was not present, the Entity Model Designer would automatically create a Many to Many relationship between entity A and entity B. However, because this field exists in the database the designer won't do it for me. I can delete the Field_I_want_to_ignore from the LinkTable Entity that the designer created for me, but how do I eliminate the LinkTable entity altogether and create the many to many relationship I want? I'm not averse to digging through the XML, just at the moment I can't see how to achieve what I want.

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  • What is the best database structure for this scenario?

    - by Ricketts
    I have a database that is holding real estate MLS (Multiple Listing Service) data. Currently, I have a single table that holds all the listing attributes (price, address, sqft, etc.). There are several different property types (residential, commercial, rental, income, land, etc.) and each property type share a majority of the attributes, but there are a few that are unique to that property type. My question is the shared attributes are in excess of 250 fields and this seems like too many fields to have in a single table. My thought is I could break them out into an EAV (Entity-Attribute-Value) format, but I've read many bad things about that and it would make running queries a real pain as any of the 250 fields could be searched on. If I were to go that route, I'd literally have to pull all the data out of the EAV table, grouped by listing id, merge it on the application side, then run my query against the in memory object collection. This also does not seem very efficient. I am looking for some ideas or recommendations on which way to proceed. Perhaps the 250+ field table is the only way to proceed. Just as a note, I'm using SQL Server 2012, .NET 4.5 w/ Entity Framework 5, C# and data is passed to asp.net web application via WCF service. Thanks in advance.

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  • Mapping one to one foreign key relationships in Entity Framework 4.0?

    - by John K.
    Hello all, I'm sure I'm missing something very simple, but let's say I have two entities, Employee and EmployeeType. Employee type would contain values like 'Full time', 'Contractor', 'Intern', etc. An Employee entity would contain one, and only one EmployeeType value. So I am designing a new .edmx model using the Model-First approach and generating my actual sql server data schema from the model. I want to add an integer type foreign key id into my Employee entity, EmployeeTypeId, which will map to the primary key of the EmployeeType entity. So I've gone ahead and done that in my Employee entity. Where I'm stuck is how, though the Entity Framework designer, to enforce the 1:1 referential constraint on that EmployeeTypeId property? Or does the EF handle that automatically behind the scenes? thanks in advance, John

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  • in .net, what programming model would be good for prototyping, but then reusable for production (for

    - by Greg
    Hi, In .NET land what would be a good approach for quick prototyping of a concept (i.e. development just on my PC) that could then be extended out to product (users across LAN/WAN), BUT in a fashion that the model/business logic code and data access layer code can be used as is? One thought for example I had as to do: (a) WinForms with business logic and Entity Framework layer to SQL Server Express on my PC, then (b) Go then to ASP.net (using the business logic / data library) with SQL Server/IIS Any comments? Other suggestions?

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  • How to avoid multiple, unused has_many associations when using multiple models for the same entity (

    - by mikep
    Hello, I'm looking for a nice, Ruby/Rails-esque solution for something. I'm trying to split up some data using multiple tables, rather than just using one gigantic table. My reasoning is pretty much to try and avoid the performance drop that would come with having a big table. So, rather than have one table called books, I have multiple tables: books1, books2, books3, etc. (I know that I could use a partition, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end First off, for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. Is there's some sort of special Ruby/Rails methodology that could be applied here to avoid having to have all of those has_many associations? Also, does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class?

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