You have two employees with the same Primary Key in the Context. Update all the properties
private void Update(Employee employee)
{
var e = _repoEmployee.GetById(employee.Id);
_unitOfWorkAsync.BeginTransaction();
e.FirstName = employee.FirstName;
e.LastName = employee.LastName;ZZ
_repoEmployee.Update(e);
_unitOfWorkAsync.SaveChanges();
_unitOfWorkAsync.Commit();
}