entity-framework

问题 I am trying to deploy a Windows desktop application with service layer, logic layer and data layer. The data layer uses SQL Server with EF 6.2. The UI client layer is a Windows Forms application. The application works great in test debug mode when the service is hosted by the WcfSvcUtil.exe application with a service alias in IIS - no errors and all data retrieval and updates are working in test. Now, I have published the Service layer, logic layer and data layer as an empty web site to be

问题 Error message: The operation cannot be completed because the dbcontext has been disposed. Can somebody explain why and where my DbContext is getting disposed while I perform the update? Context file: using System.Data.Entity; namespace OnlineTest { internal class OnlineTestContext : DbContext { private OnlineTestContext() : base("name=OnlineTest") { } private static OnlineTestContext _instance; public static OnlineTestContext GetInstance { get { if (_instance == null) { _instance = new

问题 Got the following datamodel: class EntityA { Guid Id { get; set; } //Property1 and Property2 will never be the same EntityB Property1 { get; set; } EntityB Property2 { get; set; } } class EntityB { int Id { get; set; } EntityA EntityAProperty { get; set; } } But I can't manage to configure the relation. EntityA references two different EntityB. Please give me some advise on how to configure it. Tried something like (for property1 and property2): e.HasOne(x => x.Property1) .WithOne()

问题 Is it possible to select distinct property values of an entity where the column name is not known in advance - received by the method as a string from the client. For filtering purposes I want to make a HTTP POST Ajax request to the server from the browser which will contain the field name as a key, and this will be available to the server as a string. I know I am going to have to manually map any differences between the ViewModel and the POCO class used by Entity Framework, but is it

问题 I'm working on a project that uses EFCore 2.1.0-preview1-final code first approach. Like in EF6 (and previous versions) I want to ensure the compatibility of my DbContext (and models) to the database. In EF6 it was enabled by default and it was possible to deactivate it with Database.CompatibleWithModel(false);. As far as I know EF uses the __MigrationHistory table where the model information was stored. EFCore has no such column in __EFMigrationsHistory table that could provide such

问题 I have two classes public class InvoiceRow { public int Id { get; set; } public int InvoiceId { get; set; } public int ProductId { get; set; } public virtual Product Product { get; set; } public int Amount { get; set; } } public class Invoice { public int Id { get; set; } private ICollection<InvoiceRow> _rows; public virtual ICollection<InvoiceRow> Rows => _rows ?? (_rows = new List<InvoiceRow>()); } I use Update method in the repository class public void Update(Invoice record) { dB.Invoices

问题 I have a .Net Standard 2.0 class library project and I want to add Entity Framework to it. I have added the Entity Framework Core package to the project but no Entity Framework Templates appear when I try to add a new item to the project. I have looked on the web and all I can seem to find is instructions for Code First! How do I get the database first functionality back? 回答1: EF Core does not, and will never, support the EDMX-based Database First workflow with the designer. EF Core stores

问题 I have a .Net Standard 2.0 class library project and I want to add Entity Framework to it. I have added the Entity Framework Core package to the project but no Entity Framework Templates appear when I try to add a new item to the project. I have looked on the web and all I can seem to find is instructions for Code First! How do I get the database first functionality back? 回答1: EF Core does not, and will never, support the EDMX-based Database First workflow with the designer. EF Core stores

问题 Using EntityFramework code-first, I've created a simple Foo table. Here's my entity: public class Foo { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public virtual string Id { get; set; } public virtual string Name { get; set; } } However whenever I try to insert a new row, I get a Cannot insert the value NULL into column 'Id' . Why is this happening when I've added a DatabaseGenerated attribute? Deleting and recreating my table makes no difference. 回答1: Identities for string column

问题 I have an entity with a foreign key relationship to an asp.net membership provider users table. This portion of the model looks like this: I can't seem to assign the foreign key relationship when inserting the Users table record, the record containing the foreign key to the aspnet_Users table. I keep getting the error: An item with the same key has already been added. The code I'm using looks like: UserAdmin userToAdd = new UserAdmin(); ... userToAdd.aspnet_Users = membershipUser; //line