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();

        }