看起来 EF Core 正在执行 INSERT 而不是 UPDATE,因此 MySQL 会抱怨重复键。但是,我在 DbSet 上使用 Update 方法,并且实体确实设置了主键。这会导致 MySql 中出现 DUPLICATE ENTRY 错误。
运行 VS 2019、EF Core 3.1.1 和 ASP.NET Core 3.1
模型(我不使用 Fluent 配置来建立关系,只是使用约定):
public class Vehicle
{
public long Id {get; set; } // PRIMARY KEY, AUTO INCREMENT
public string RegistrationNumber { get; set; }
public VehicleSession Session { get; set; }
}
public class VehicleSession
{
public long VehicleId { get; set; }
public Vehicle Vehicle { get; set; }
public string DeviceUuid { get; set; } // PRIMARY KEY
public string AuthenticationToken { get; set; }
public string OSName { get; set; }
public string OSVersion { get; set; }
public string DeviceModel { get; set; }
}
数据库:
表“vehiclesessions”,其中主键是 DeviceUuid 并且具有键“device2”:
控制器:
请求从某处传来。 DeviceUuid 是从 HTTP 标头中获取的。
public async Task<ActionResult<VehicleLoginResponse>> Login(VehicleLogin login)
{
Request.Headers.TryGetValue(BaseConstants.DEVICE_UUID, out StringValues deviceUuid);
Vehicle vehicle = await vehicleService.Authenticate(login.Username, login.Password); // returns a Vehicle by asking dbContet: dbContext.Vehicles.FirstOrDefault(v => v.Username.Equals(username));
VehicleSession vs = await vehicleService.CreateSession(vehicle, login, deviceUuid);
// ...
}
Service:
该服务创建一个新的VehicleSession对象,将其分配给Vehicle属性,并对Vehicle执行.Update,以便用它保存新会话。
public async Task<VehicleSession> CreateSession(Vehicle vehicle, VehicleLogin vehicleLogin, string deviceUuid)
{
VehicleSession vs = new VehicleSession()
{
Vehicle = vehicle,
AuthenticationToken = someTokenFetchedFromSomewhere,
DeviceModel = vehicleLogin.DeviceModel,
DeviceUuid = deviceUuid, // is 'device2'
OSName = vehicleLogin.OSName,
OSVersion = vehicleLogin.OSVersion
};
vehicle.Session = vs;
dbContext.Vehicles.Update(vehicle);
await dbContext.SaveChangesAsync();
return vs;
}
如果我更换也没关系new VehicleSession
和分配,只需编辑现有的 Vehicle.Session,同样的错误:
public async Task<VehicleSession> CreateSession(Vehicle vehicle, VehicleLogin vehicleLogin, string deviceUuid)
{
if (vehicle.Session == null)
vehicle.Session = new VehicleSession(); // never executes this line
vehicle.Session.AuthenticationToken = someTokenFetchedFromSomewhere;
vehicle.Session.DeviceModel = vehicleLogin.DeviceModel;
vehicle.Session.DeviceUuid = deviceUuid;
vehicle.Session.OSName = vehicleLogin.OSName;
vehicle.Session.OSVersion = vehicleLogin.OSVersion;
await dbContext.SaveChangesAsync();
return vehicle.Session;
}
这样做时,我收到一条错误消息:
Microsoft.EntityFrameworkCore.DbUpdateException:发生错误
更新条目时。有关详细信息,请参阅内部异常。 --->
MySql.Data.MySqlClient.MySqlException(0x80004005):重复条目
'device2' 代表关键 'vehiclesessions.PRIMARY' --->
MySql.Data.MySqlClient.MySqlException(0x80004005):重复条目
关键“vehiclesessions.PRIMARY”的“device2”
SQL 产生:
Failed executing DbCommand (125ms) [Parameters=[@p0='?' (Size = 95), @p1='?' (Size = 95), @p2='?' (Size = 4000), @p3='?' (Size = 4000), @p4='?' (Size = 4000), @p5='?' (DbType = Int64)], CommandType='Text', CommandTimeout='30']
INSERT INTO `VehicleSessions` (`DeviceUuid`, `AuthenticationToken`, `DeviceModel`, `OSName`, `OSVersion`, `VehicleId`)
VALUES (@p0, @p1, @p2, @p3, @p4, @p5);
fail: Microsoft.EntityFrameworkCore.Update[10000]
An exception occurred in the database while saving changes for context type 'blabla'.
Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
---> MySql.Data.MySqlClient.MySqlException (0x80004005): Duplicate entry 'device2' for key 'vehiclesessions.PRIMARY'
---> MySql.Data.MySqlClient.MySqlException (0x80004005): Duplicate entry 'device2' for key 'vehiclesessions.PRIMARY'
为什么我会收到此错误?尽管车辆对象是从 dbContext 中获取、传递并设置了 PRIMARY id,但似乎完成了 INSERT 而不是 UPDATE。