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• Entity Framework and the XmlIgnoreAttribute

  - by Mikey Cee

  Say you have a one to one relationship in your entity model. The code generator will decorate it with the following attributes: [global::System.Xml.Serialization.XmlIgnoreAttribute()] [global::System.Xml.Serialization.SoapIgnoreAttribute()] public RelatedObject Relationship { get {...} set {...} } I want to serialize my parent object together with all its properties for which data has been loaded through an XML web service. Obviously, these related properties do not get serialized because of these attributes. So for my purposes I just want to remove these "don't serialize me" attributes. I can do a find and replace in the designer code, but any modifications I make in the designer will put these attributes back in. How do I permanently get rid of these attributes? VS 2008 / EF 3.5.

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• Changing an extention method from linq-to-sql to entity framework

  - by Jova

  I'm changing my project from working with Linq-to-SQL to working with Entity Framework. I have some extention methods that extend the classes created by LINQ and I'm wondering how to change them to work with the entities instead Here's an example. public static int GetPublishedArticlesCount(this Table<Article> source) { return GetPublishedArticles(source.Context as DataContext, null).Count(); } This method gets the number of published articles. Instead of using this Table<Article>, what should I use instead?

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• Entity Framework 5 vs Telerik OpenAccess ORM (specifically)

  - by dimoss

  I am starting a new project and want advice on choosing an ORM. I know this topic has been brought up before, but this topic is specific to either Entity Framework 5 (not 4) or Telerik OpenAccess ORM. The project will reside on Windows Azure and use Windows Azure SQL Database. I will migrate it to .NET 4.5 once 4.5 is live on Azure. I am currently a Telerik Ultimate Collection subscriber. Does anyone in the know have any pros/cons for this scenario? I am slightly leaning towards Telerik OpenAccess at the moment. Thanks

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• Entity Framework Performance Inconsistency Compared to Sql Management Studio

  - by AndyV

  I'm getting timeouts with a very basic EF statement. I'm simply doing a select from a single table with a Entity.Title.StartsWith("test") and a .Take(25). When I run this for a search that returns no results I get a timeout. If I profile and grab the sql statement it looks fine, and if I run that sql in Management Studio it runs in a fraction of a second! Why would the same query run sub-second in Management Studio and timeout when generated by EF and called from an Asp.Net app?

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• EF Code First - Include(x => x.Properties.Entity) a 1 : Many association

  - by VulgarBinary

  Given a EF-Code First CTP5 entity layout like: public class Person { ... } which has a collection of: public class Address { ... } which has a single association of: public class Mailbox { ... } I want to do: PersonQuery.Include(x => x.Addresses).Include("Addresses.Mailbox") WITHOUT using a magic string. I want to do it using a lambda expression. I am aware what I typed above will compile and will bring back all Persons matching the search criteria with their addresses and each addresses' mailbox eager loaded, but it's in a string which irritates me. How do I do it without a string? Thanks Stack!

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• How to estimate size of data to transfer when using DbCommand.ExecuteXXX?

  - by Yadyn

  I want to show the user detailed progress information when performing potentially lengthy database operations. Specifically, when inserting/updating data that may be on the order of hundreds of KB or MB. Currently, I'm using in-memory DataTables and DataRows which are then synced with the database via TableAdapter.Update calls. This works fine and dandy, but the single call leaves little opportunity to glean any kind of progress info to show to the user. I have no idea how much data is passing through the network to the remote DB or its progress. Basically, all I know is when Update returns and it is assumed complete (barring any errors or exceptions). But this means all I can show is 0% and then a pause and then 100%. I can count the number of rows, even going so far to cound how many are actually Modified or Added, and I could even maybe calculate per DataRow its estimated size based on the datatype of each column, using sizeof for value types like int and checking length for things like strings or byte arrays. With that, I could probably determine, before updating, an estimated total transfer size, but I'm still stuck without any progress info once Update is called on the TableAdapter. Am I stuck just using an indeterminate progress bar or mouse waiting cursor? Would I need to radically change our data access layer to be able to hook into this kind of information? Even if I can't get it down to the precise KB transferred (like a web browser file download progress bar), could I at least know when each DataRow/DataTable finishes or something? How do you best show this kind of progress info using ADO.NET?

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• Help me understand entity framework 4 caching for lazy loading

  - by Chris

  I am getting some unexpected behaviour with entity framework 4.0 and I am hoping someone can help me understand this. I am using the northwind database for the purposes of this question. I am also using the default code generator (not poco or self tracking). I am expecting that anytime I query the context for the framework to only make a round trip if I have not already fetched those objects. I do get this behaviour if I turn off lazy loading. Currently in my application I am breifly turning on lazy loading and then turning it back off so I can get the desired behaviour. That pretty much sucks, so please help. Here is a good code example that can demonstrate my problem. Public Sub ManyRoundTrips() context.ContextOptions.LazyLoadingEnabled = True Dim employees As List(Of Employee) = context.Employees.Execute(System.Data.Objects.MergeOption.AppendOnly).ToList() 'makes unnessesary round trip to the database, I just loaded the employees' MessageBox.Show(context.Employees.Where(Function(x) x.EmployeeID < 10).ToList().Count) context.Orders.Execute(System.Data.Objects.MergeOption.AppendOnly) For Each emp As Employee In employees 'makes unnessesary trip to database every time despite orders being pre loaded.' Dim i As Integer = emp.Orders.Count Next End Sub Public Sub OneRoundTrip() context.ContextOptions.LazyLoadingEnabled = True Dim employees As List(Of Employee) = context.Employees.Include("Orders").Execute(System.Data.Objects.MergeOption.AppendOnly).ToList() MessageBox.Show(employees.Where(Function(x) x.EmployeeID < 10).ToList().Count) For Each emp As Employee In employees Dim i As Integer = emp.Orders.Count Next End Sub Why is the first block of code making unnessesary round trips?

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• EF problem with entity re-ordering and uniqueness constraint

  - by wpfwannabe

  I am using Entity Framework and I've come to an interesting stumbling block. Let's say there is a db table "Item" with "sequence" column of type int (and others of course). Column "sequence" must be unique and it is used for (re)ordering of items. EF maps this table to "Item" class with "sequence" int property. Now let's say I want to swap position of two items by mutually exchanging each other's sequence number. Upon calling SaveChanges() EF throws an exception complaining about "sequence" uniqueness. It probably generates two UPDATEs and the first one probably fails. I assume that plain SQL solution to this issue is using a third UPDATE to introduce a unique sequence value in the process but I am stuck with EF. Any thoughts?

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• Entity Framework does not display the last change from the database

  - by Jack

  Entity Framework does not display the last change from the database, but after sometime it show the updated content. I don't any special change on the server or on the page. Thank in advance. Jack Here is the code i use to get the list: var m = from r in ett.Article_Relations from i in ett.Article_Articles from a in ett.Article_Contents where r.MenuItemID == id && r.Article_Articles.ArticleID == i.ArticleID && a.LanguageID == LanguageID && i.ArticleID == a.Article_Articles.ArticleID select new ArticleViewModel { ArticleID = i.ArticleID, IsActive = i.IsActive, Author = i.ArticleAuthor, Content = a, DateCreated = i.DateCreated };

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• Entity Framework doesn't like 0..1 to * relationships.

  - by Orion Adrian

  I have a database framework where I have two tables. The first table has a single column that is an identity and primary key. The second table contains two columns. One is a nvarchar primary key and the other is a nullable foreign key to the first table. On the default import of the database I get the following error: Condition cannot be specified for Column member 'ForeignKeyId' because it is marked with a 'Computed' or 'Identity' StoreGeneratedPattern. where ForeignKeyId is the second foreign key reference in the second table. Is this just something the entity model doesn't do? Or am I missing something?

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• Entity Framework with File-Based Database

  - by Dave Swersky

  I am in the process of developing a desktop application that needs a database. The application is currently targeted to SQL Express 2005 and works wonderfully. However, I'm not crazy about having this dependency on SQL Express and would prefer to use a small file-based database. My problem is that I am using Entity Framework. I have tried both SQL Compact and SQLite, and they both have bizarre problems with EF v1. I get errors creating the Model, invalid models when it does get created... it's a nightmare. I'm about ready to give up and write a data layer and repository in the good-old-school Connection/Command pattern. Not my favorite plan... Is there a lightweight, file-based database out there that plays well with EF? OR Is there a better ORM tool that I should use instead of EF with my lightweight DB?

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• Automapping to EntityKeys in Entity Framework

  - by CodeGrue

  Does anyone have a technique to automap (using Automapper) references to child entities. So say I have a ViewModel: class AddressModel { int Id; string Street; StateModel State; } class StateModel { int Id; string Name; } And I pass this into a repository to map to equivalent entities in Entity Framework. When Automapping, I want it to automap AddressModel.State.ID to the EntityKey of AddressEntity.StateReference. So hand crafted code would look like this: addressEntity.Id = AddressModel.Id; addressEntity.Street = AddressModel.Street addressEntity.StateReference.EntityKey = new EntityKey("MyDB.States", "Id", AddressModel.State.Id); Obviously, when automapper tries to assign an Address.State.Id to the equivalent in EF, an exception is thrown.

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• Using entity framework to detect changes in related table and action appropriate inserts and deletes

  - by Kohan

  Lets say i have a Person table, a Role table with a trel table PersonRoles linking them as many to many. I create a new person and assign them to 2 roles (role 1, role 3). I then want to edit this person; so i retrieve their data and bind their roles to a checkboxes. I change the values (Deselect role 1 and select role 2 instead) I then post this data back through a viewmodel. Can i then get Entity Framework to update these roles for me, as in delete the entry in PersonRoles to role 1 and then add a new entry as role 2? Or do i have to do the logic for this myself? Cheers, Kohan

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• Call function in query in Entity framework 3.5

  - by Ashwani K

  Hello All: I am trying to run following query in entity framework 3.5 var test = from e in customers where IsValid(e) select e; Here IsValid function takes current customer and validate against some conditions and returns false or true. But when I am trying to run the query it is giving error "LINQ Method cannot be translated into a store expression." Can any body tell me any other approach? One approach I can think of is to write all validation conditions here, but that will make the code difficult to read. Thanks Ashwani

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• Entity Framework 4: C# !(ReferenceEquals()) vs !=

  - by Eric J.

  Unless a class specifically overrides the behavior defined for Object, ReferenceEquals and == do the same thing... compare references. In property setters, I have commonly used the pattern private MyType myProperty; public MyType MyProperty { set { if (myProperty != value) { myProperty = value; // Do stuff like NotifyPropertyChanged } } } However, in code generated by Entity Framework, the if statement is replaced by if (!ReferenceEquals(myProperty, value)) Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden). Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==? In short, if I have not overridden ==, am I save using != instead of ReferencEquals()?

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• C# Entity Framework Base Repository

  - by Andy

  I'm trying to create a base repository for use with Entity Framework 4.0 and having some trouble. In this code below, why is it not possible to do this in one line? public IEnumerable<T> GetAll<T>(Expression<Func<T, bool>> filter) { IEnumerable<T> allCustomers = this.GetAll<T>(); IEnumerable<T> result = allCustomers.Where(filter.Compile()); return result; } Won't this result in 2 SQL statements: one without a where clause that retrieves all rows, and one with a where clause that only retrieves the rows that match the predicate? How can this be done with a single SQL statement? I can't get it to compile if I try to cast the filter.Compile() to Func<Customer, bool>. Thanks, Andy

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• How to deal with data on the model specific to the technology being used?

  - by user1620696

  There are some cases where some of the data on a class of the domain model of an application seems to be dependent on the technology being used. One example of this is the following: suppose we are building one application in .NET such that there's the need of an Employee class. Suppose further that we are going to implement relational database, then the Employee has a primary key right? So that the classe would be something like public class Employee { public int EmployeeID { get; set; } public string Name { get; set; } ... } Now, that EmployeeID is dependent on the technology right? That's something that has to do with the way we've choose to persist our data. Should we write down a class independent of such things? If we do it this way, how should we work? I think I would need to map all the time between domain model and persistence specific types, but I'm not sure.

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• Binding Navigation Property with Entity Framework

  - by JSmaga

  Hi, I have another question about binding using C# and the entity framework. Here, I'm looking to bind a navigation property to a listbox or a listview. I saw on different posts that if I update the collection using code behind the list would not be notified because the collection does not handle notification (it's always the same problem anyway). People suggested to use an ObservableCollection for example, but, and here is my question, this comes down to basically duplicate the collection and hence, if I modify it, I'd have to handle in code-behind the fact that the change has also to be applied to the "original" navigation property right? If that's the case, I was thinking: why not create a custom property called, say, MyObservableNavigationProperty in a partial class. I could then interact only with this collection, catch the event when the collection is changed and apply the change to the "original" collection. Is that a nice way to do the trick? or am I getting all confused here....

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• Is EF4 "Code Only" ready for production use?

  - by Tommy Jakobsen

  I've been looking at the new Entity Framework 4 Code Only features, and I really like them. But I'm having a hard time finding good resource on the feature. Everything seems to be spread around blongs here and there, so this make me wonder if it's ready to be used for a serious project? What do you think? Is it ready for production use or should I use the more traditional approach (EDMX designer, POCO objects)? Also, I would like to know if there are any features that Code Only does not support yet, compared to the EDMX designer? What do you think about the Code Only feature? Is it "mature" yet? Thank you.

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• Entity Framework 4.0 Unit Testing

  - by Steve Ward

  Hi, I've implemented unit testing along the lines of this article with a fake object context and IObjectSet with POCO in EF4. http://blogs.msdn.com/adonet/archive/2009/12/17/test-driven-development-walkthrough-with-the-entity-framework-4-0.aspx But I'm unsure how to implement a couple of methods on my fake object context for testing. I have CreateQuery and ExecuteFunction methods on my object context interface so that I can execute ESQL and Stored Procedures but I cant (easily) implement them in my fake object context. An alternative would be to use a test double of my repository instead of a double of my object context as suggested here: http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/c4921443-e8a3-4414-92dd-eba1480a07ad/ But this would mean my real repository isnt being tested and would seem to just bypass the issue. Can anyone offer any recommendations?

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• Enumerable.Range in and Expression and Entity Framework

  - by eka808

  I'm currently developping an expression method (used in linq to entity queries) who has to give me a daycount for a given period (start date and end date) decrementing this daycount if specials days are in the period. My idea was the following : Generate an enumerable with all the dates (and with Enumerable.Range) Make a .Where on this enumerable to remove the specials dates Like a MyEnumerable.Where(a = a != "20120101") After that, return a MyEnumerable.Count() I come with this code : return (p) => Enumerable .Range(1, 4) .Where(a => a != 20120101) .AsQueryable() .Count() I tried to cast as a list, as a queryable, both (like the example) and no way ! it doesn't work ! I always get this error : LINQ to Entities does not recognize the method 'System.Collections.Generic.IEnumerable`1[System.Int32] Range(Int32, Int32)' method, and this method cannot be translated into a store expression. Have you got an idea about that ? Using an enumerable is of course not mandatory, any working solutions is good ^^ Thank's by advance !

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• Association in Entity Framework 4

  - by Marsharks

  I have two tables, a problem table and a problem history table. As you can expect, a problem can have many histories associated with it. CREATE TABLE [dbo].[Problem]( [Last_Update] [datetime] NULL, [Problem_Id] [int] NOT NULL, [Incident_Count] [int] NULL ) ALTER TABLE [dbo].[Problem] ADD CONSTRAINT [PK_Problem] PRIMARY KEY CLUSTERED ( [Problem_Id] ASC ) CREATE TABLE [dbo].[Problem_History]( [Last_Update] [datetime] NULL, [Problem_Id] [int] NOT NULL, [Severity_Chg_Flag] [char](1) NULL ) ALTER TABLE [dbo].[Problem_History] ADD [Create_DateTime] [datetime] NOT NULL ALTER TABLE [dbo].[Problem_History] WITH CHECK ADD CONSTRAINT [FK_Problem_History_Problem] FOREIGN KEY([Problem_Id]) REFERENCES [dbo].[Problem] ([Problem_Id]) The problem is when I drag this into an Entity Model, the associations are not included. Any ideas? I would like to point out that the problem history table has no separate key of its own, it shares the problem id

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• Entity Framework: a proxy collection for displaying a subset of data

  - by Jefim

  Imagine I have an entity called Product and a repository for it: public class Product { public int Id { get; set; } public bool IsHidden { get; set; } } public class ProductRepository { public ObservableCollection<Product> AllProducts { get; set; } public ObservableCollection<Product> HiddenProducts { get; set; } } All products contains every single Product in the database, while HiddenProducts must only contain those, whose IsHidden == true. I wrote the type as ObservableCollection<Product>, but it does not have to be that. The goal is to have HiddenProducts collection be like a proxy to AllProducts with filtering capabilities and for it to refresh every time when IsHidden attribute of a Product is changed. Is there a normal way to do this? Or maybe my logic is wrong and this could be done is a better way?

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• Saving Data to Relational Database (Entity Framework)

  - by sheefy

  I'm having a little bit of trouble saving data to a database. Basically, I have a main table that has associations to other tables (Example Below). Tbl_Listing ID UserID - Associated to ID in User Table CategoryID - Associated to ID in Category Table LevelID - Associated to ID in Level Table. Name Address Normally, it's easy for me to add data to the DB (using Entity Framework). However, I'm not sure how to add data to the fields with associations. The numerous ID fields just need to hold an int value that corresponds with the ID in the associated table. For example; when I try to access the column in the following manner I get a "Object reference not set to an instance of an object." error. Listing NewListing = new Listing(); NewListing.Tbl_User.ID = 1; NewListing.Tbl_Category.ID = 2; ... DBEntities.AddToListingSet(NewListing); DBEntities.SaveChanges(); I am using NewListing.Tbl_User.ID instead of NewListing.UserID because the UserID field is not available through intellisense. If I try and create an object for each related field I get a "The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects." error. With this method, I am trying to add the object without the .ID shown above - example NewListing.User = UserObject. I know this should be simple as I just want to reference the ID from the associated table in the main Listing's table. Any help would be greatly appreciated. Thanks in advance, -S

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• Entity Framework 4.0 - Code only Reference

  - by joe

  Hello All, I am trying to learn EF 4 and its code only features. I tried the following great articles and was able to make a sample application. http://blogs.taiga.nl/martijn/2009/11/22/entity-framework-4-0-a-fresh-start-with-demo-application/#reply http://blogs.msdn.com/efdesign/archive/2009/10/12/code-only-further-enhancements.aspx But I am looking for a good reference library / website on Code only feature. I tried searching MSDN but couldn't find it. Please help. Thanks a lot.

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