我有一个 Employee
对象,我正在尝试使用单个 DB 实体上下文使用多个任务 (并行执行) 更新记录(即更新/删除)。但是,我得到了以下异常:
消息 = "对象引用未设置为对象的实例。"
考虑以下数据传输对象(DTO):
public class Employee
{
public int EmployeeId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public List<ContactPhone> ContactPhoneNumbers { get; set; }
public List<ContactEmail> ContactEmailAddress { get; set; }
}
public class ContactPhone
{
public int ContactId { get; set; }
public string Type { get; set; }
public string Number { get; set; }
}
public class ContactEmail
{
public int ContactId { get; set; }
public string Type { get; set; }
public string Number { get; set; }
}
员工表:
EmployeeId FirstName LastName
_________________________________
1 Bala Manigandan
ContactPhone 表:
ContactId EmployeeId Type Number
__________________________________________
1 1 Fax 9123456789
2 1 Mobile 9123456789
联系电话表:
ContactId EmployeeId Type EmailAddress
______________________________________________
1 1 Private bala@gmail.com
2 1 Public bala@ymail.com
传入的API对象是:
DTO.Employee emp = new DTO.Employee()
{
EmployeeId = 1,
FirstName = "Bala",
LastName = "Manigandan",
ContactPhoneNumbers = new List<DTO.ContactPhone>
{
new DTO.ContactPhone()
{
Type = "Mobile",
Number = "9000012345"
}
},
ContactEmailAddress = new List<DTO.ContactEmail>()
{
new DTO.ContactEmail()
{
Type = "Private",
EmailAddress = "bala@gmail.com"
},
new DTO.ContactEmail()
{
Type = "Public",
EmailAddress = "bala@ymail.com"
}
}
};
我收到一条API请求,要求更新指定员工的手机号码并删除传真号码。
考虑以下任务方法:
public void ProcessEmployee(DTO.Employee employee)
{
if(employee != null)
{
DevDBEntities dbContext = new DevDBEntities();
DbContextTransaction dbTransaction = dbContext.Database.BeginTransaction();
List<Task> taskList = new List<Task>();
List<bool> transactionStatus = new List<bool>();
try
{
Employee emp = dbContext.Employees.FirstOrDefault(m => m.EmployeeId == employee.EmployeeId);
if (emp != null)
{
Task task1 = Task.Factory.StartNew(() =>
{
bool flag = UpdateContactPhone(emp.EmployeeId, employee.ContactPhoneNumbers.FirstOrDefault().Type, employee.ContactPhoneNumbers.FirstOrDefault().Number, dbContext).Result;
transactionStatus.Add(flag);
});
taskList.Add(task1);
Task task2 = Task.Factory.StartNew(() =>
{
bool flag = RemoveContactPhone(emp.EmployeeId, "Fax", dbContext).Result;
transactionStatus.Add(flag);
});
taskList.Add(task2);
}
if(taskList.Any())
{
Task.WaitAll(taskList.ToArray());
}
}
catch
{
dbTransaction.Rollback();
}
finally
{
if(transactionStatus.Any(m => !m))
{
dbTransaction.Rollback();
}
else
{
dbTransaction.Commit();
}
dbTransaction.Dispose();
dbContext.Dispose();
}
}
}
public async Task<bool> UpdateContactPhone(int empId, string type, string newPhone, DevDBEntities dbContext)
{
bool flag = false;
try
{
var empPhone = dbContext.ContactPhones.FirstOrDefault(m => (m.EmployeeId == empId) && (m.Type == type));
if (empPhone != null)
{
empPhone.Number = newPhone;
await dbContext.SaveChangesAsync();
flag = true;
}
}
catch (Exception ex)
{
throw ex;
}
return flag;
}
public async Task<bool> RemoveContactPhone(int empId, string type, DevDBEntities dbContext)
{
bool flag = false;
try
{
var empPhone = dbContext.ContactPhones.FirstOrDefault(m => (m.EmployeeId == empId) && (m.Type == type));
if (empPhone != null)
{
dbContext.ContactPhones.Remove(empPhone);
await dbContext.SaveChangesAsync();
flag = true;
}
}
catch (Exception ex)
{
throw ex;
}
return flag;
}
我遇到了以下异常:
消息 = “对象引用未设置为对象的实例。”
这里我附上屏幕截图供您参考
我的要求是使用Task并行执行所有数据库UPSERT
操作,敬请指导如何在不出现任何异常的情况下实现
employee.ContactPhoneNumbers.FirstOrDefault().Type, employee.ContactPhoneNumbers.FirstOrDefault()
。另外,DbContext 不是线程安全的,因此在线程中操作上下文时要小心。 - Developer