如何首先在Entity Framework代码中创建2个具有相同类型的dbset？ [英] How to create 2 dbsets with the same type in Entity Framework code first?

问题描述

我创建了2个代表数据库实体的类。

I created 2 classes which represent entities for a database.

第一个实体：

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 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：

When I try to use this code:

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);
}

我收到此错误

不支持每种类型的多个对象集。对象集 Flights和 FlightsArchive都可以包含类型为 Project_Airline_Info.Models.Flight的实例。

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'.

所以我的问题如何在DbContext类中创建具有相同泛型的2个DBset。

So my question is how to create 2 DBsets with same generic type,in DbContext class.

推荐答案

简短的答案是您不能这样做。考虑以下代码行：

The short answer is that you can't do this. Consider this line of code:

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

如何知道要使用哪个集合来获取数据？

How does it know which set to use to get the data?

可能最简单的解决方法是继承 Flight 类，并将其用于其他 DbSet ：

Probably the simplest workaround would be to inherit the Flight class and use that for your other DbSet:

public class ArchiveFlight : Flight
{
}

以及您的环境：

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将属性添加到已归档文件中航班，例如存档日期：

The bonus of doing this is that you can now add properties to your archived flights, such as the date it was archived:

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

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