EF6 SqlException:违反主键约束.重复的键值是(0)

Question

我知道SQL，但我对ORM非常陌生，在2017年使用EntityFramework 6.2.0玩沙箱。我认为框架应该使我能够或多或少地像使用POCO对象那样编码，而不必处理主/外键。当我调用下面的代码context.SaveChanges()时，这些更改就会保存在数据库中；对于EF6及其文档，我还不了解什么呢？

我使用外键和1:n关系创建了两个表Person和WorkingHours。

  CREATE TABLE [dbo].[Person](
    [FirstName] [nvarchar](100) NOT NULL,
    [LastName] [nvarchar](100) NOT NULL,
    [BirthDate] [date] NULL,
    [Id] [int] IDENTITY(1,1) NOT NULL,
 CONSTRAINT [PK_Person] PRIMARY KEY CLUSTERED 
(
    [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

CREATE TABLE [dbo].[WorkingHours](
  [Id] [int] NOT NULL,
  [PersonId] [int] NOT NULL,
  [Date] [date] NOT NULL,
  [Start] [time](7) NOT NULL,
  [Hours] [real] NOT NULL,
 CONSTRAINT [PK_WorkingHours] PRIMARY KEY CLUSTERED 
(
  [Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

I从数据库.创建了模型

我尝试创建两个Person条目，每个条目都带有一个WorkingHours条目，并立即将其保存到数据库中。以下是代码：

     static void Main(string[] args)
    {
        using(var context = new EntityFrameworkTrialEntities2())
        {
             // Inserting entries
            var person1 = new Person() { FirstName = "Al", LastName = "Curie", BirthDate = new DateTime(1867, 11, 7) };
            var person2 = new Person() { FirstName = "Al", LastName = "Capone", BirthDate = new DateTime(1899, 1, 7) };
            context.Person.Add(person1);
            context.Person.Add(person2);

            var workingHour1 = new WorkingHour() { Date = new DateTime(1887, 8, 18), Start = new TimeSpan(6, 35, 33), Hours = 4.3F };
            var workingHour2 = new WorkingHour() { Date = new DateTime(1919, 9, 19), Start = new TimeSpan(10, 23, 56), Hours = 3.2F };
            person2.WorkingHours.Add(workingHour1); 
            person1.WorkingHours.Add(workingHour2); 

            context.WorkingHours.Add(workingHour1);
            context.WorkingHours.Add(workingHour2);
            context.SaveChanges(); // <-- place of exeception !!!!!!!!!!!!!!!!!!!!

            // (next step as EF6 trial: here the previously intentionally mixed relationships between person1/2 and workingHour2/1 shall be corrected)

但是在调用context.SaveChanges()时，我得到了这个异常：

SqlException:违反主键约束 'PK_WorkingHours‘。无法在对象'dbo.WorkingHours‘中插入重复键。重复的键值为(0)。语句已终止。**

我尝试了不同的方式，更多的context.SaveChanges()和附加()和其他命令，但我总是失败，除了上述例外。context.Configuration.ProxyCreationEnabled设置为true为默认值。

在这里，模型类：

public partial class Person
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public Person()
    {
        this.WorkingHours = new HashSet<WorkingHour>();
    }

    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Nullable<System.DateTime> BirthDate { get; set; }
    public int Id { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<WorkingHour> WorkingHours { get; set; }
}


public partial class WorkingHour
{
    public int Id { get; set; }
    public int PersonId { get; set; }
    public System.DateTime Date { get; set; }
    public System.TimeSpan Start { get; set; }
    public float Hours { get; set; }

    public virtual Person Person { get; set; }
}

Answer 1

第一个问题是主键 WorkingHour不是Identity Key，这就是为什么每个WorkingHour总是将其设置为0 (默认值int)，因此被复制。

因此，使Id列的WorkingHour [Id] [int] IDENTITY(1,1) NOT NULL

第二个问题出现在以下几行：

person2.WorkingHours.Add(workingHour1); // adding with person
person1.WorkingHours.Add(workingHour2); // adding with person

context.WorkingHours.Add(workingHour1); // adding individually
context.WorkingHours.Add(workingHour2); // adding individually

在这里，您将在上下文中添加两次WorkingHour。一个带有Person实体，另一个是单独的。因此，移除第二组，只需按以下方式使用第一组：

person2.WorkingHours.Add(workingHour1); 
person1.WorkingHours.Add(workingHour2);

Answer 2

我认为你的问题是因为[Id] in [WorkingHours]

  CREATE TABLE [dbo].[WorkingHours](
      [Id] [int] NOT NULL,
      [PersonId] [int] NOT NULL,
      [Date] [date] NOT NULL,
      [Start] [time](7) NOT NULL,
      [Hours] [real] NOT NULL,
     CONSTRAINT [PK_WorkingHours] PRIMARY KEY CLUSTERED 
    (
      [Id] ASC
    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    ) ON [PRIMARY]

按下面的方式更改，然后再试一次。

 CREATE TABLE [dbo].[WorkingHours](
      [Id] [int] IDENTITY(1,1) NOT NULL,
      [PersonId] [int] NOT NULL,
      [Date] [date] NOT NULL,
      [Start] [time](7) NOT NULL,
      [Hours] [real] NOT NULL,
     CONSTRAINT [PK_WorkingHours] PRIMARY KEY CLUSTERED 
    (
      [Id] ASC
    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    ) ON [PRIMARY]