c# – 如何首先在Entity Framework代码中创建具有相同类型的2个d

发布时间：2020-12-15 04:19:33 所属栏目：百科来源：网络整理

导读：我创建了2个表示数据库实体的类. 第一实体： public enum FlightStatus{ checkIn,gateClosed,arrived,departedAt,unknown,canceled,expectedAt,delayed,InFlight}public class Flight { [Key] public string FlightNumber { get; set; } public DateTime Arr

我创建了2个表示数据库实体的类.

第一实体：

public enum FlightStatus
{
        checkIn,gateClosed,arrived,departedAt,unknown,canceled,expectedAt,delayed,InFlight
}

public class Flight 
{
        [Key]
        public string FlightNumber { get; set; }
        public DateTime Arrival { get; set; }
        public DateTime Departure { get; set; }
        public string CityOfArrival { get; set; }
        public string CityOfDeparture { get; set; }
        public char Terminal { get; set; }

        public FlightStatus Status { get; set; }
        public int Gate { get; set; }

        public virtual ICollection<Passanger> PassengerList { get; set; }
        public double PriceForFirstClass { get; set; }
        public double PriceForBusiness { get; set; }
        public double PriceForEconom { get; set; }
}

第二实体：

public enum Sex
{
        M,F
}

public enum FlightClass
{
        First,Business,Econom,}

public enum TicketType
{
        OneWay,TwoWay,}

public class Passenger
{
        [Key]
        public string Passport { get; set; }
        public string flightNumber { get; set; }

        [ForeignKey("flightNumber")]
        public virtual Flight flight { get; set; }      

        public string FirstName { get; set; }
        public string SecondName { get; set; }
        public string Nationality { get; set; }       
        public DateTime DateOfbirthday { get; set; }
        public Sex SexOfPassanger { get; set; }
        public FlightClass ClassForPassanger { get; set; }
        public TicketType TypeOfTicket { get; set; }
}

然后我创建了一个DbContext：

class FlightsDatabase : DbContext
{
    public DbSet<Flight> Flights { get; set; }
    public DbSet<Flight> FlightsArchive { get; set; }

    public DbSet<Passenger> Passengers { get; set; }
}

当我尝试使用此代码时：

using (FlightsDatabase flights = new FlightsDatabase())
{
    foreach (Flight flight in flights.Flights)
    {
        if (Math.Abs((flight.Departure - DateTime.Now).Days) <= 1)
        {
            timeCame(flight,null);
        }

        if (flight.Departure < DateTime.Now)
        {
            flightsToClean.Add(flight);
        }
    }

    moveOldFlights(flightsToClean,null);
}

我收到这个错误

Multiple object sets per type are not supported. The object sets ‘Flights’ and ‘FlightsArchive’ can both contain instances of type ‘Project_Airline_Info.Models.Flight’.

所以我的问题是如何在DbContext类中创建具有相同泛型类型的2个DBset.

解决方法

简短的回答是你不能这样做.考虑以下代码行：

var flight = context.Set<Flight>().Where(f => f.FlightNumber = "123");

它如何知道用于获取数据的集合？

可能最简单的解决方法是继承Flight类并将其用于其他DbSet：

public class ArchiveFlight : Flight
{
}

你的背景：

public class FlightsDatabase :DbContext
{
    public DbSet<Flight> Flights { get; set; }
    public DbSet<ArchiveFlight> FlightsArchive { get; set; }
    public DbSet<Passanger> Passengers { get; set; }
}

这样做的好处是,您现在可以向归档的航班添加属性,例如归档日期：

public class ArchiveFlight : Flight
{
    public DateTime DateArchived { get; set; }
}

（编辑：李大同）

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