Question

我知道SQL，但是我对ORM还是很陌生，可以在VS 2017中使用EntityFramework 6.2.0在沙箱中玩游戏。我认为该框架应该使我能够像使用POCO对象一样或多或少地进行编码，而不必处理主键/外键。我在下面的代码上下文中调用后，更改便立即保存在数据库中。 EF6及其文档我还不了解什么？

我使用外键和1：n关系创建了两个相互依赖的表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]

我从数据库中创建了模型。

我尝试创建两个Person条目，每个条目都有一个WorkingHours条目，并将其立即保存到数据库中。这是代码：

     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（）;时我收到此异常：

SqlException：违反了PRIMARY KEY约束'PK_WorkingHours'。无法在对象'dbo.WorkingHours'中插入重复的密钥。 重复的键值为（0）。 该声明已终止。**

我用更多的context.SaveChanges（）和Attach（）以及其他命令尝试了不同的方式，但是由于上述异常我总是失败。默认将context.Configuration.ProxyCreationEnabled设置为true。

这里是模型类：

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WorkingHour的主键不是Identity Key，因此始终将其设置为0（默认值{{1 }}），每个int都被复制。

因此，将WorkingHour Id的{{1}}列

第二个问题是以下几行：

WorkingHour

这里您要在上下文中添加两次[Id] [int] IDENTITY(1,1) NOT NULL。一个带有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实体，另一个带有单独实体。因此，删除第二组，只需按如下方式使用第一组即可：

WorkingHour

Answer 2

我认为您的问题是由于[Id]中的[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]

按如下所示进行更改，然后重试。

 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]

EF6 SqlException：违反PRIMARY KEY约束...重复的键值为（0）

2 个答案: