“NameOfProperty”不能用作实体类型“NameOfType”的属性，因为它被配置为导航

Question

我有一个带有船舶和预订导航属性的数据库的预订和船舶类别，

    public class Reservation {
        public Reservation() {
            Ship = new Ship();
        }
        public int Id { get; set; }
        public DateTime FromDate { get; set; }
        public DateTime ToDate { get; set; }
       [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public Ship Ship { get; set; }
   }

    public class Ship {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Port{ get; set; }
        public List<Reservation> Reservations { get; set; }
    }

DBcontext.cs 文件：

        protected override void OnModelCreating(ModelBuilder modelBuilder) {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Reservation>().HasOne(r => r.Ship).WithMany(s => s.Reservations);
            modelBuilder.Entity<Reservation>().HasOne(u => u.Person).WithMany(r => r.Reservations);
            modelBuilder.Entity<Ship>().HasMany(res => res.Reservations).WithOne(s => s.Ship);

            //This line generates the error
            modelBuilder.Entity<Reservation>().Property(a => a.Ship).ValueGeneratedNever();
        }

        public DbSet<Reservation> Reservations { get; set; }
        public DbSet<Ship> Ships { get; set; }
    }
}

我添加生成错误的这一行和下面的 executeSqlRawAsync 方法的原因是我试图解决这个错误： Microsoft.Data.SqlClient.SqlException (0x80131904): Cannot insert explicit value for identity column in table 'Ships ' 当 IDENTITY_INSERT 设置为 OFF 时。` 我想在数据库中创建一个带有船的预订，但我不能插入一个值。所以我尝试用这个 ValueGeneragtedNever 方法和 executeRawSql 方法修复它，但它给了我标题中的错误。

public async Task CreateReservation(ReservationGetDTO reservationDTO)
        {
            await _context.Database.ExecuteSqlRawAsync("SET IDENTITY_INSERT [dbo].[Reservations] ON");
            _context.Reservations.Add(Mapper.Map(reservationDTO, new Reservation()));
            await _context.SaveChangesAsync();
            await _context.Database.ExecuteSqlRawAsync("SET IDENTITY_INSERT [dbo].[Reservations] OFF");
        }

任何想法我错过了什么？

Answer 1

这不起作用的另一个原因是我在按下提交按钮后尝试向客户端的导航属性添加值。但您只能在服务器端为导航属性添加值。

Answer 2

修复预留类，移除 [DatabaseGenerated(DatabaseGeneratedOption.None)] 和构造函数

public class Reservation {
       
        public int Id { get; set; }
        public DateTime FromDate { get; set; }
        public DateTime ToDate { get; set; }

        public int ShipId { get; set; }
        public virtual  Ship Ship { get; set; }
   }

    public class Ship {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Port{ get; set; }
        public virtual  ICollection<Reservation> Reservations { get; set; }
    }

并且由于您使用的是 ef core 5+ 从 dbcontext 中删除所有流式 API，因此您不需要它们

并尝试使用此代码添加新项目

public async Task CreateReservation(ReservationGetDTO reservationDTO)
        {
           
          _context.Reservations.Add(Mapper.Map(reservationDTO, new Reservation()));
            await _context.SaveChangesAsync();
           
        }