C# 为什么实体框架给我一个关于不存在的数据的错误

我正在使用mvc5和实体框架代码优先迁移 我尝试为表设置种子，但收到以下错误消息：

The INSERT statement conflicted with the FOREIGN KEY constraint 
"FK_dbo.Orders_dbo.Users_UserId". The conflict occurred in database 
"DbDemo.Models.DbbContext", table "dbo.Users", column 'Id'.
The statement has been terminated.

我知道有人说，在播种订单之前，数据必须已经存在于users表中，但users中的

userid

是一个主键，所以我认为它是自动播种的，因为它的identity=true！那我为什么会犯这个错误呢

public class User
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Email { get; set; }
    public string Password { get; set; }
    public string PhoneNum { get; set; }
    public string Location { get; set; }
    public string Type { get; set; }
}

public class Order
{
    [Key]
    [Column(Order = 1)]
    public int Id { get; set; }

    //ForeignKey from Items table for the composite key
    [Key]
    [Column(Order = 2)]
    public int? ItemId { get; set; }
    public Item Item { get; set; }

    //ForeignKey from Users table
    public int? UserId { get; set; }
    public User User { get; set; }

    public int Quantity { get; set; }
    public int? TotalPrice { get; set; } //why did i put this field??!
}

这是用户种子迁移：

public partial class UsersSeed : DbMigration
{
    public override void Up()
    {
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('Khaled Tahboub', 'khaledk.tahboub@gmail.com', 'abc@123', '0797504280', 'Amman', 'A')");
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('Muath Mustafa', 'muathmustafa@gmail.com', 'abc@123', '0797504280', 'Amman', 'A')");
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('John Doe', 'JohnDoe@gmail.com', 'abc@123', '0797504280', 'Amman', 'B')");
    }

    public override void Down()
    {
    }
}

public partial class OrdersSeed : DbMigration
{
    public override void Up()
    {
        Sql("insert into Orders (UserId, ItemId, Quantity) values (1, 1, 1)");
    }

    public override void Down()
    {
    }
}

这是种子迁移的顺序：

public partial class UsersSeed : DbMigration
{
    public override void Up()
    {
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('Khaled Tahboub', 'khaledk.tahboub@gmail.com', 'abc@123', '0797504280', 'Amman', 'A')");
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('Muath Mustafa', 'muathmustafa@gmail.com', 'abc@123', '0797504280', 'Amman', 'A')");
        Sql("insert into Users (Name,Email,Password,PhoneNum,Location,Type) values ('John Doe', 'JohnDoe@gmail.com', 'abc@123', '0797504280', 'Amman', 'B')");
    }

    public override void Down()
    {
    }
}

public partial class OrdersSeed : DbMigration
{
    public override void Up()
    {
        Sql("insert into Orders (UserId, ItemId, Quantity) values (1, 1, 1)");
    }

    public override void Down()
    {
    }
}

---

这意味着您试图插入一个用户ID在用户表中不存在的订单。您是否试图同时创建订单和新用户？请出示你用来做这项工作的代码。我刚刚在帖子中提供了代码。这是第一个代码吗？用户类缺少将Id定义为键/标识的属性，您也缺少指示实体框架订购的属性。UserId是对Users.Id的FK。