如何使用Entity Framework生成和自动增加Id

Question

修改了整个帖子.

我正试图通过Fiddler发布以下JSON POST请求:

{Username:"Bob", FirstName:"Foo", LastName:"Bar", Password:"123", Headline:"Tuna"}

但是我收到了这个错误:

Message "Cannot insert the value NULL into column 'Id', table 'xxx_f8dc97e46f8b49c2b825439607e89b59.dbo.User'; column does not allow nulls. INSERT fails.\r\nThe statement has been terminated." string

虽然如果我手动发送随机ID和请求,那么一切都很好.像这样:

{Id:"1", Username:"Bob", FirstName:"Foo", LastName:"Bar", Password:"123", Headline:"Tuna"}

为什么实体框架不会生成并自动增加Id？我的POCO课程如下:

public class User
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public string Id { get; set; }
    public string Username { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Password { get; set; }
    public string Headline { get; set; }
    public virtual ICollection<Connection> Connections { get; set; }
    public virtual ICollection<Address> Addresses { get; set; }
    public virtual ICollection<Phonenumber> Phonenumbers { get; set; }
    public virtual ICollection<Email> Emails { get; set; }
    public virtual ICollection<Position> Positions { get; set; }
}

public class Connection
{
    public string ConnectionId { get; set; }
    public int UserId { get; set; }
    public virtual User User { get; set; }
}

public class Phonenumber
{
    public string Id { get; set; }
    public string Number { get; set; }
    public int Cycle { get; set; }
    public int UserId { get; set; }
    public User User { get; set; }
}

这是控制器方法.当处于调试模式并且我通过Fiddler发送请求时,它会中断db.SaveChanges();并在上面看到错误.

    // POST api/xxx/create
    [ActionName("create")]
    public HttpResponseMessage PostUser(User user)
    {
        if (ModelState.IsValid)
        {
            db.Users.Add(user);
            db.SaveChanges();

            HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, user);
            response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = user.Id }));
            return response;
        }
        else
        {
            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
        }
    }

怎么了？

解

将字符串Id更改为int,然后删除Data annotations.将Id重命名为UserId,仍遵循惯例,并在必要时在其他POCO中进行更改以匹配更改.

Answer 1

这是猜:)

是因为ID是一个字符串吗？如果将其更改为int会发生什么？

我的意思是:

 public int Id { get; set; }

Answer 2

你有一个糟糕的桌面设计.你不能自动增加一个字符串,这没有任何意义.你基本上有两个选择:

1.)改变ID的类型int而不是字符串
2.)不推荐!!! - 自己处理自动增量.首先需要从数据库中获取最新值,将其解析为整数,然后将其递增并再次将其作为字符串附加到实体.很糟糕的主意

第一个选项需要更改每个引用此表的表,但这是值得的.