“NameOfProperty”不能用作物體型別“NameOfType”的屬性，因為它被配置為導航-有解無憂

我有一個帶有 Ship 和 Reservations 導航屬性的 DB 的預訂和船類，

    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 檔案：

        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; }
    }
}

我添加生成錯誤的這一行和下面的 executeSqlRawAsync 方法的原因是我試圖解決這個錯誤：Microsoft.Data.SqlClient.SqlException (0x80131904)：當 IDENTITY_INSERT 時，無法為表 'Ships' 中的標識列插入顯式值設定為 OFF。` 我想在 DB 中創建一個帶有船的預訂，但我無法插入值。所以我嘗試用這個 ValueGeneragtedNever 方法和 executeRawSql 方法修復它，但它給了我標題中的錯誤。

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");
        }

任何想法我錯過了什么？

uj5u.com熱心網友回復：

修復保留類，移除 [DatabaseGenerated(DatabaseGeneratedOption.None)] 和建構式

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 ，因此從 dbcontext 中洗掉了所有流暢的 API，因此您不需要它們

并嘗試使用此代碼添加新專案

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

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