entity-framework-4

问题 I was getting an error An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key. After i googled it i found IsAttachedTo extension method there: Is is possible to check if an object is already attached to a data context in Entity Framework? here is my code: foreach (string s in types) { Subscription subscription = new Subscription { Id = Int32.Parse(s) }; if (service.repository._context.IsAttachedTo

问题 I am using EF4 CTP5 to try to persist a POCO object that is split among two tables, the link being the ContactID. When i save a contact, i want the core contact information saved in one table (Contacts), and the link to the user who owns the contact saved in another (UserToContacts). I have the custom mapping defined below, but when I SaveChanges, i get the following error: A value shared across entities or associations is generated in more than one location. Check that mapping does not split

问题 I've got the following entities on my EDMX :- These two entites were generated by Update Model From Database . Now, notice how my country has the following primary key :- Name & IsoCode this is because each country is UNIQUE in the system by Name and IsoCode. Now, with my States ... it's similar. Primary Key is :- Name & CountryId Each state is unique by name and per country. Now, the Foreign Key for States is a CountryId. This is the sql :- ALTER TABLE [dbo].[States] WITH CHECK ADD

问题 I can't figure out why I get this error when I try to add a Venue object and call SaveChanges(). The only difference in the model with Venue objects is they are 1 to 1..0 relation with City. City city = ProcessCityCache(ev, country, db); // After this call, 'city' is already persisted. venue = new Venue { TicketMasterURL = ev.VenueSeoLink, Name = Capitalize(ev.VenueName), City = city }; db.Venues.AddObject(venue); db.SaveChanges(); // Exception thrown here. Any insight would be greatly

问题 I have an enumeration which I'd like to persist as a value of some sort into the underlying database so that I can bring it back and forth. I have read some articles that suggest to create a enumeration wrapper with static implicit operators defined, mapped using a ComplexType object mapping as described in the link below. How to fake Enums in EF4 This solution works flawlessly! My thanks to Alex James. Aside, I discovered of the EnumDataTypeAttribute Class which purpose seems to handle enums

问题 My application needs to display a table of customer data, including data about the customer and about his most recent order from a given warehouse. The customer domain object contains a GetLatestOrder(warehouseId) method. I have a CustomerView viewmodel and want to be able to populate it with some fields from the customer object, and a few fields from the latest order object. Can I do this using Automapper? 回答1: Try this, In Global.asax.cs [ Application_Start ], public static void

问题 I am developing a WPF desktop app that uses Entity Framework 4 and SQL Compact 4. I have seen two distinct styles of Repository classes: The Repository instantiates an ObjectContext , which is disposed of when the Repository is garbage-collected. The lifetime of the ObjectContext is the same as the lifetime of the application. A separate DataStoreManager class creates and holds an ObjectContext for the life of the application. When a repository is needed, a command gets an ObjectContext

问题 Has anyone here used MySQL with the entity framework 4.0 and stored procedures? When I add a SP, it does not show any of my fields that I need to input. I also see no way to manually add them. When I click Function Import Mapping, it simply says "Select an Entity or Association on the Entity Designer Model Browser to edit it's mapping". Any help is appreciated. I am using the .NET Connector 6.3.6 回答1: due to the bug #55778 (Stored procedure parameters are omitted during update of the entity

问题 I read that the new Entity Framework will include a method to delete multiple items (Linq to SQL has DeleteAllOnSubmit()) but I can't find the function/method to do that. Is this in Beta 2 or do I have to make my own? UPDATE: This is what I'm using now: public void DeleteObjects(IEnumerable<object> objects) { foreach (object o in objects) { DeleteObject(o); } SaveChanges(); } 回答1: EF 4 allows you to execute TSQL statements against an object context: using (var context = new

问题 I'm done trying to Google for this. I have installed SQL Server CE 4.0, and have EF 4.1, but I can't get a proper connection string. Nothing on connectionstrings.com applies to me. I just want to create a SqlCeEngine object, but no matter what I try I get some exception. Most recently it's been Unknown connection option in connection string with either "metadata", "app", "provider", or "provider connection string" after it. I know EF requires metadata in the connection string. And I can't