问实体框架7关系问题

EN

public class User {
    // Primary key
    public int Id {get;set;}
    // Some attributes
    public string FirstName {get; set;} 
    public string LastName {get; set;}
    // Foreign keys
    public int CityOfBirthId {get;set;}
    public int CityHomeId {get;set;}
    // Navigation methods
    [ForeignKey("CityOfBirthId")]
    public virtual City CityOfBirth {get;set;}
    [ForeignKey("CityHomeId")]
    public virtual City CityHome {get;set;}
}

public class City {
    // Primary key
    public int Id {get;set;}
    // Attributes
    public string Name {get;set;}
    // Navigation methods
    [InverseProperty("CityOfBirth")]
    public virtual ICollection<User> UsersBorn {get;set;}
    [InverseProperty("CityHome")]
    public virtual ICollection<User> UsersHome {get;set;}
}

public DbSet<User> Users {get;set;}
public DbSet<City> Cities {get;set;}