entity framwork修改指定字段

1、ef修改时指修改指定字段
public void ChangePassword(int userId, string password)
{
  var user = new User() { Id = userId, Password = password };
  using (var db = new MyEfContextName())
  {
    db.Users.Attach(user);
    db.Entry(user).Property(x => x.Password).IsModified = true;
    db.SaveChanges();
  }
}
2、ef修改时指定字段不被修改

 public void UpdateCustomer()
        {

            // 自己实例化要更新对象 省了访问数据库获取数据时间
            Customer customer3 = new Customer();
            customer3.Id = 22;            
            customer3.CustAddress = "北京25";
            List<string> listRmoveFiled = new List<string>();
            listRmoveFiled = "CustCode,CustName".Split(',').ToList<string>();

            CustoemrRepository cuR = new CustoemrRepository();            
            int row = cuR.UpdateModel(customer3,listRmoveFiled);
        }

 /// 修改实体对象
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        public int UpdateModel(TEntity model, List<string> listRemoveField = null)
        {

            // 排除不需更新的字段            
            foreach (string field in listRemoveField)
            {
                if (field != "Id")
                    unDbContext.Entry(model).Property(field).IsModified = false;
            }

            if (unDbContext.Entry<TEntity>(model).State == System.Data.Entity.EntityState.Detached)
            {
                //将model追加到EF容器                
                unDbContext.Entry(model).State = EntityState.Modified;
            }
            return unDbContext.SaveChanges();
        }