从MVC服务删除项目时出错

Question

I am getting this error after click Delete:

 try
        {
            var crews = await GetCrewsAttached(id);
            var assetbookings = await _assetBooking.Get(id);
            var parts = await GetParts("LTD", id, false);
            //Checks if records exist in assetbookings and the employee not attached to any crew and doesnt have any parts associated to the employee
            if (assetbookings == null && (crews.Count() == 0 || crews == null) && (parts == null || parts.ToList().Count() == 0))
            {
                var employee = await _employeeRepository.Get(
                  e => e.EmployeeID == id,
                  new List<Expression<Func<gblEmployee, object>>>() {
                    (e => e.Address),
                    (e => e.EmployeeTraining.Select(t=>t.Training)),
                    (e => e.EmployeeWorkSchedule)
                });

                if (employee != null && employee.IsSupervisor != true)
                {
                    foreach (var training in employee.EmployeeTraining)
                    {
                        _employeeTrainingRepository.Delete(training);
                    }
                    await _employeeTrainingRepository.Commit();


                    if (employee.Address != null)
                    {
                        _addressRepository.Delete(employee.Address);
                        await _addressRepository.Commit();
                    }
                    _employeeRepository.Delete(employee);
                    await _employeeRepository.Commit();


                }
            }
        }
        catch (Exception ex)
        {
            throw new NexgenException(ex);
        }

I am getting Error at await _employeeRepository.Commit();

Any Method to Resolve ? Error is The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted

Answer 1

Try to call .SaveChanges before the commit. Also you can create a catch block that catches a DbEntityValidationException so you can check for missing values