entity-framework-4

问题 For example: namespace PizzaSoftware.Data { public class User { public string Username { get; set; } public string Password { get; set; } public Permission PermissionType { get; set; } } public enum Permission { Basic, Administrator } } If if I were to use Entity-Framework's CodeFirst, how can I save this value? This is for a Windows Forms, Desktop application. Thank you! 回答1: You can retrieve the int value (or whatever type you have your enum set to) via a simple cast and save that to the DB

问题 We have an application with three layers: UI, Business, and Data. The data layer houses Entity Framework v4 and auto-generates our entity objects. I have created a buddy class for the entity VendorInfo : namespace Company.DataAccess { [MetadataType(typeof(VendorInfoMetadata))] public partial class VendorInfo { } public class VendorInfoMetadata { [Required] public string Title; [Required] public string Link; [Required] public string LinkText; [Required] public string Description; } } I want

问题 I'm trying to resolve an error very similar to the one outlined here: InvalidOperationException when calling SaveChanges in .NET Entity framework It appears that the solution (which I have not tried yet, admittedly) is to pass System.Data.Objects.SaveOptions.None as the SaveOptions parameter for the SaveChanges() method. So before I do that, I'm trying to understand exactly how the different SaveOptions work (None, AcceptAllChangesAfterSave, DetectAllChanges). I haven't been able to find a

问题 I have an Entity Framework Code First DbContext with the following entities configured. In this example class Bar is a child of class Foo. public class Foo { public Guid Id { get; set; } public virtual ICollection<Bar> Bars { get; set; } } public class Bar { public Guid Id { get; set; } public Guid FooId { get; set; } public virtual Foo Foo { get; set; } } Now I know that internally, Entity Framework understands that the relationship between Foo and Bar is defined by the foreign key Bar.FooId

问题 Well, it seems like I'm stuck in my application structure. Here's what I want to do: UI layer: An ASP.NET webforms website. BLL: Business logic layer which calls the repositories on DAL. DAL: .EDMX file (Entity Model) and ObjectContext with Repository classes which abstract the CRUD operations for each entity. Entities: The POCO Entities. Persistence Ignorant. Generated by Microsoft's ADO.Net POCO Entity Generator. I'd like to create an obejctcontext per HttpContext in my repositories to

问题 Well, it seems like I'm stuck in my application structure. Here's what I want to do: UI layer: An ASP.NET webforms website. BLL: Business logic layer which calls the repositories on DAL. DAL: .EDMX file (Entity Model) and ObjectContext with Repository classes which abstract the CRUD operations for each entity. Entities: The POCO Entities. Persistence Ignorant. Generated by Microsoft's ADO.Net POCO Entity Generator. I'd like to create an obejctcontext per HttpContext in my repositories to

问题 I'm not sure about Navigational Properties in EF 4 so I would kindly ask you an explanation. Lets imagine this scenarios: A) I have two Entities A and B with a relation N to N (many to many) and tree Table in my Data Base A and B and a Link Table AB with two Foreign Key . In this scenario EF create a Navigational Property lets call it X and also a XReference . B) I have two Entities A and B with a relation 1 to N (one to many) and two Table in my Data Base A and B with one Foreign Key . In

问题 I'm trying to load related entities of a SingleOrDefault entity, but I am getting the following exception: The navigation property of type IEnumerable is not a single implementation of type ICollection I've tried doing this several ways and ultimately get the same error above for each query against the context (I've included the other ways in comments). using(var context = CustomObjectContextCreator.Create()) { return context.Job.Include("Surveys").Include("SiteInfoes") .Where(r => r.Jobid ==

问题 I am issuing an Insert statement directly against the DB (SQL Server 2008), using EF6.1 on ASP.NET 4.5. I need to get the newest ID in the transaction post insert, however I cannot quite figure out the code. This is what I have at present: db.ExecuteStoreCommand("INSERT INTO Order ([SupplierId]) Values ({0})", SID); Int32 intId = db.ExecuteStoreQuery<Int32>("SELECT SCOPE_IDENTITY()").First(); var myOrder = db.Order.First(r => r.Id == intId); The above example is simplified. Is it possible

问题 I'm used to using code first where I can do: db.Users.Attach(user); db.Entry(user).Property(propertyName).IsModified = true; How do I do this with a DataModel approach? I do not have the Entry method on my datacontext. 回答1: Use: context.Users.Attach(user); ObjectStateEntry entry = context.ObjectStateManager.GetObjectStateEntry(user); entry.SetModifiedProperty(propertyName); 来源： https://stackoverflow.com/questions/6947950/entity-framework-4-update-specific-properties