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• ADO.NET Entity Framework with OLE DB Access Data Source

  - by Tim Long

  Has anyone found a way to make the ADO.NET Entity Framework work with OLE DB or ODBC data sources? Specifically, I need to work with an Access database that for various reasons can't be upsized to SQL. This MSDN page says: The .NET Framework includes ADO.NET providers for direct access to Microsoft SQL Server (including Entity Framework support), and for indirect access to other databases with ODBC and OLE DB drivers (see .NET Framework Data Providers). For direct access to other databases, many third-party providers are available as shown below. The reference to "indirect access to other databases" is tantalising but I confess that I am hopelessly confused by all the different names for data access technology.

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• Repository Pattern with Entity Framework 3.5

  - by Ravi

  I am developing a Database File System. I am using - .Net framework 3.5 Entity Framework 3.5 WPF with MVVM pattern The project spans across multiple assemblies each using same model. One assembly,let's call it a "server", only adds data to the database using EF i.e. same model.Other assemblies (including the UI) both reads and writes the data.The changes made by server should immediately reflect in other assemblies. The database contains self referencing tables where each entity can have single OR no parent and (may be) some children. I want to use repository pattern which can also provide some mechanism to handle this hierarchical nature. I have already done reading on this on Code Project. It shares the same context(entities) everywhere. My question is - Should I share the same context everywhere? What are the advantages and disadvantages of doing that?

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• Repository Pattern with Entity Framework 3.5

  - by Ravi

  I am developing a Database File System. I am using - .Net framework 3.5 Entity Framework 3.5 WPF with MVVM pattern The project spans across multiple assemblies each using same model. One assembly,let's call it a "server", only adds data to the database using EF i.e. same model.Other assemblies (including the UI) both reads and writes the data.The changes made by server should immediately reflect in other assemblies. The database contains self referencing tables where each entity can have single OR no parent and (may be) some children. I want to use repository pattern which can also provide some mechanism to handle this hierarchical nature. I have already done reading on this on Code Project. It shares the same context(entities) everywhere. My question is - Should I share the same context everywhere? What are the advantages and disadvantages of doing that?

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• Entity framework createquery question.

  - by Tony Heflin

  I am trying to create a generic search form to use in an EF app. I want to be ably to specify the entity to query at runtime below is a simplified version of the code. cx is the contect object, valuelists is the entity in question. 1: Dim q As String = "select c from intactentities.valuelists as c" 2: Dim x = cx.CreateQuery(Of ValueLists)(q) 3: TextBox1.Text = x.Count This works but I need to remove the hardcoded reference to valuelists in line 3. I expect I am overlooking something simple can anyone suggest a simple solution? Thanks Tony

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• insert and modify a record in an entity using Core Data

  - by aminfar

  I tried to find the answer of my question on the internet, but I could not. I have a simple entity in Core data that has a Value attribute (that is integer) and a Date attribute. I want to define two methods in my .m file. First method is the ADD method. It takes two arguments: an integer value (entered by user in UI) and a date (current date by default). and then insert a record into the entity based on the arguments. Second method is like an increment method. It uses the Date as a key to find a record and then increment the integer value of that record. I don't know how to write these methods. (assume that we have an Array Controller for the table in the xib file)

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• Using Repository and Unit of Work patterns with Entity Framework 4.0 and MVC 2

  - by Mr. D

  Hi, I'm following this article Using Repository and Unit of Work patterns with Entity Framework 4.0. I'm tying to implement the Repository and Unit of work pattern, using Asp.Net MVC 2 and Entity Framework 4. Please let me know if I'm doing it right... In the Models folder: Northwind.edmx Products.cs (POCO class) ProductRepository.cs (Did my product query) IProductRepository.cs NorthwindContext.cs IUnitOfWork.cs In the Controller folder: ProductController.cs (Retrieve from ProductRepository.cs and Pass it to the view) When I run the application, I'm getting error message: Mapping and metadata information could not be found for EntityType 'NorthwindMvcPoco.Models.Category'. I don't know what I'm doing wrong. I search through whole web and I couldn't resolve this issue. Please help me.

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• Generating Entity Keys

  - by David Veeneman

  I have run into my first dissapointment with Entity Framework 4. It turns out that SQL CE, when used with EF4, does not support autogenerated primary keys. I get a System.Data.UpdateException from OnjectContext.SaveChanges() with this message: Server-generated keys and server-generated values are not supported by SQL Server Compact. So, now I have to manually generate keys for my entities. Assuming I want to use auto-incremented integer keys, what is the best way to go about generating and keeping track of the keys when using Entity Framework? Thanks for your help.

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• Entity Framework - Medium Trust

  - by Echilon

  I'm trying to get the entity framework working in medium trust. I've tried splitting the files and using a separate assembly but I seem to have one problem after another. I moved the EDMX to a separate assembly, which causes a single .dll to be outpit to the sites /Bin directory. I'm referencing this as below from web.config. Whenever I try to access one of the entity classes, I get an ArgumentException: 'An item with the same key has already been added.' It's critical this works with medium trust, but I seem to be running out of options. Any advice greatly appreciated.

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• Entity Frameworks 4 - Changing the model does not update the T4 self tracking template files

  - by Darren

  I am using self tracking entities and have moved the entity classes to another assembly by using 'Add as link' to point to the TT file as mentioned here. Now though, when I update the model (for instance change a property name) the template is not automatically run and so the entity class does not get updated. I can of course manually run the template to get the updates, but it would be easier if it ran automatically in the way it did before I moved the classes. Is there any way to achieve this? Darren.

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• insert and mofigy a record in an entity using Core Data

  - by aminfar

  I tried to find the answer of my question on the internet, but I could not. I have a simple entity in Core data that has a Value attribute (that is integer) and a Date attribute. I want to define two methods in my .m file. First method is the ADD method. It takes two arguments: an integer value (entered by user in UI) and a date (current date by default). and then insert a record into the entity based on the arguments. Second method is like an increment method. It uses the Date as a key to find a record and then increment the integer value of that record. I don't know how to write these methods. (assume that we have an Array Controller for the table in the xib file)

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• Entity Framework + SQLite deployment

  - by Pompair

  Hi, I have a ASP.NET MVC app that is using SQLite database through Entity Framework. Everything works on VS 2008's local development webserver. However, deploying the web app to my service provider causes this error: [ArgumentException: Unable to find the requested .Net Framework Data Provider. It may not be installed.] System.Data.Common.DbProviderFactories.GetFactory(String providerInvariantName) +1308959 System.Data.EntityClient.EntityConnection.GetFactory(String providerString) +35 Service provider has commented that they do not support SQLite. I had though that SQLite is independent of service provider's settings since it's App_Data deployable. Has anyone experiences of a succesfull Entity Framework + SQLite deployment? Cheers, -pom-

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• Generate Entity Data Model from Data Contract

  - by CSmooth.net

  I would like to find a fast way to convert a Data Contract to a Entity Data Model. Consider the following Data Contract: [DataContract] class PigeonHouse { [DataMember] public string housename; [DataMember] public List<Pigeon> pigeons; } [DataContract] class Pigeon { [DataMember] public string name; [DataMember] public int numberOfWings; [DataMember] public int age; } Is there an easy way to create an ADO.NET Entity Data Model from this code?

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• VS2010 MVC and Entity Framework Model in Separate Project

  - by mdm

  Hi, I am trying to use an Entity Framework Model (in separate project) into an asp.net 4 MVC project (VS2010, C#) If I create the EF inside the MVC project I have no problems. I think I am missing some step. things done: 1. added reference to the EF class project 2. added connection string in MVC web.config 3. added reference to System.Data.Entity in both web.config and project references Now i can use the model only if I copy the .edmx file to the Models folder, but in this way the EF project is not external anymore. What am I missing? Thank you in advance.

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• Entity Framework Performance Problem

  - by Steve Horn

  I'm hoping that someone can help me understand how to overcome a performance problem I'm running into with the latest version of the Entity Framework. In my test, I created my model from a database consisting of around 80 tables. The problem that I'm running into is that the cost of the very first query I run on a thread is very expensive. If I run without pre-compiling views the first query takes anywhere from 5800 to 6600 milliseconds. If I pre-compile the views (see this article) I can get the initial query cost down to about 2800 to 3200 milliseconds. 3 seconds for each request is still unacceptable for my needs. Subsequent queries are very fast. Can you please help me understand how to eliminate the poor performance of the initial query? I'm using the version of entity framework that ships with Visual Studio 2010 RC.

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• ADO.NET Entity Model and LINQ

  - by Richard

  Hi all I'm using an ADO.NET Entity Model which I'm trying to query using LINQ. The problem I'm having is that I can't specify the where clause as I'd like. For instance, consider the following query: AccountsDM db = new AccountsDM(ConfigurationManager.ConnectionStrings["PrimaryEF"].ConnectionString); var accounts = from a in db.Accounts select a; foreach (var account in accounts) { foreach (var ident in account.Identifiers) { if (ident.Identifier == identifier) { // ident.Identifier is what I'd like to be filtering in the WHERE clause below } } } Ideally, I'd like that to become: var accounts = from a in db.Accounts where a.Identifiers.Identifier == identifier select a; I'm guessing I've probably not set up my Entity Model correctly in VS2010. Any advice you can offer would be gratefully received. Thanks, Richard.

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• Validate data using DataAnnotations with WPF & Entity Framework?

  - by Shimmy

  Hello is thee any way to validate using Data Using DataAnnotations in WPF & Entity Framework?

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• Entity framework - exclude list of values

  - by DutrowLLC

  Is there a way to exclude a list of values for an object attribute when querying the database through entity framework? I tried to be slick and pull this number: List<String> StringList = new List<String>(); StringList.Add("ya_mama"); StringList.Add("has"); StringList.Add("fleas"); servicesEntities context = new servicesEntities(); var NoFleasQuery = (from x in context.person where !StringList.Any(y => y.CompareTo(x.the_string_I_dont_want_it_to_be) == 0) // <--- the part where I thought I was slick select x); ...it compiled, but after I ran it, it gave me this error: Unable to create a constant value of type 'Closure type'. Only primitive types ('such as Int32, String, and Guid') are supported in this context. 'Closure type'???? How about MY closure!!! Entity framework... you broke my heart.

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• Need Help on entity framework

  - by Sarathi1904

  I have 3 tables(Roles,Actions and RoleActionLinks). Roles table has few columns(RoleID,RoleName,Desc). Actions table has few colums(ActionID,ActionName,Desc). In RoleActionLink is created for store the association between Roles and Actions and this table has the columns such as RoleID,ActionID When I created the data model(edmx). it shows only Role and Action as entity. i did not find RoleActionLink table. but even there is no direct relation between Roles and Actions table, both tables are automatically related using RoleActionLink table. When i create the new Action, a action record should be populated in Action table(this is works fine). At the same time, i need to populate record in RoleActionLinks table. But i dont have the entity to populate. Please tell me how to accomplish my needs.

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• Entity Framework use of indexes and foreign keys

  - by David

  I want to be able to search a table quite quickly using the Entity Framework, say if I have a Contacts table, a JobsToDo table and a matrix table linking the two tables e.g Contacts_JobsToDo_Mtx and I specify two foreign keys in the Contacts_JobsToDo_Mtx table, if I wanted to search this Mtx table, do I need to specify an index on the two foreign keys? Or by the fact that they are two foreign keys are they considered indexed on them anyway? Will the Entity Framework be able to search through the Mtx table quickly without having to specfiy an index on both keys? Thanks!

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• EF Code First Detached Entity not updating object reference

  - by Alvaro

  I'm posting the exact entity: public class Person : ContactableEntity { public Plan Plan { get; set; } public int Record { get; set; } public int PersonTypeValue { get; set; } } I'm using the following code to update in a disconected context fashion: public void Update(DbSet MySet, object Obj) { MySet.Attach(Obj); var Entry = this.Entry(Obj); Entry.State = EntityState.Modified; this.SaveChanges(); } This is a method exposed by my dbContext Called this way: PersistentManager.Update(PersistentManager.Personas,UpdatedPersona); The problem is, EF will update any property but the referenced Plan object. Can someone tell me where is the mistake? In advance : the entity reaches the point of update with all the properties correctly set. EF just fails to update the FK in the Database (no exception though)

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• Entity Fremework serialization

  - by Alexandr

  Hello guys! I was confused with my problem. I'm using Entity Framework and want to save entities on hard disk and then to restore them. I have no problem with Serializing/Deserializing but i get an exception "The object cannot be added to the ObjectStateManager because it already has an EntityKey. Use ObjectContext.Attach to attach an object that has an existing key" when i try to add deserialized object to my datacontext. And nothing happens when i just Attach my entity to datacontext How to achieve my goal? Thx in advance! -Alexandr-

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• ASP.NET MVC & ADO.NET Entity Framework clientside validation

  - by JK

  Using aspnet mvc2 with the model auto-generated by entity framework: Is it possible to tell entity framework to auto-annotate all fields? eg: If database field says not null then add [Required] If DB field is a nvarchar(x) then add [StringLength(x)] And so on? What if the field name contains the string "email" eg CustomerEmail - can I get EF to auto-annotate that with an appropriate annotation ([Regex()] maybe) As I understand it, if the model fields are annotated, and I use both Html.ValidationMessageFor() and use if (ModelState.IsValid) in my controller, then that is all I need to do to have basic clientside input validation working? Thanks

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• Entity Framework associations killing performance

  - by Chris

  Here is the performance test i am looking at. I have 8 different entities that are table per type. Some of the entities contain over 100 thousand rows. This particular application does several recursive calculations on the client so I think it may be best to preload the data instead of lazy loading. If there are no associations I can load the entire database in about 3 seconds. As I add associations in any way the performance starts to drastically decline. I am loading all the data the same way (just calling toList() on the entity attached to the context). I ran the test with edmx generated classes and self tracking entities and had similar results. I am sure if I were to try and deal with the associations myself, similar to how I would in a dataset, the performance problem would go away. On the other hand I am pretty sure this is not how the entity framework was intended to being used. Any thoughts or ideas?

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• Triggers in Entity Framework - Need advice

  - by jaklucky

  Hi all, I am new to Entity Framework and please pardon my ignorance. We have a simple application written using SQL Server and ADO.Net. Now we have got a new requirement that, whenever a particular rows get updated by our application, some business logic has to happen. I have been looking into Triggers in SQL server and it looks like we can do it using triggers. I am also looking at Entity Framework's OnPropertyChange capability. Is it possible to do it with "OnPropertyChange"? I mean, Can I create a model and implement "OnPropertyChange" method? And when our application modifies the rows using ADO.Net, then will it fire "OnPropertyChange" event so that my custome code in "OnPropertyChange" excutes? Thank you in advance for your inputs, Suresh

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• Dealing with uncertainty in ORM - Entity Framework CodeOnly

  - by Simon Fox

  This is a bit of a strange one but I've just seen something on twitter which kind of baffled me and I'm interested to know more. Rob Conery tweeted the following a couple of hours ago: Class name of the day: "Maybe<T>". Method of the day: "ToMaybe<T>()". He then went on to offer a Tekpub coupon to anyone who could guess where it came from. He linked to a further tweet which had a clue and from that I worked out that it was Entity Framework Code-Only but while trying to determine the usage someone else answered to which Rob replied ...EF CodeOnly - dealing with uncertainty.... So my question boils down to what exactly is he referring to with uncertainty and how does this fit in to Entity Framework Code-Only?

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