EF 如何更新少量字段

EF更新少量字段需要解决两个问题

1.动态的将需要更新的字段提取出来

2.将提取出来的字段设为更新状态

通常更新的时候，都是根据条件将实体取出来，然后赋值字段，最后更新整个实体，所以在方法上看似是更新少量字段，其实是更新了所有字段，比较浪费性能

 

获取要更新的字段列表

 /// <summary>
        /// 获取要更新的字段
        /// </summary>
        /// <param name="updateAction"></param>
        /// <returns></returns>
        private List<string> GetUpdateColumns(Action<TEntity> updateAction)
        {
            List<string> modifyColumns = new List<string>();
            TEntity modifyModel = new TEntity();
            updateAction(modifyModel);
            PropertyInfo[] proArr = typeof(TEntity).GetProperties();
            foreach (PropertyInfo info in proArr)
            {
                if (info.GetValue(modifyModel) != null)
                {
                    modifyColumns.Add(info.Name);
                }
            }
            return modifyColumns;
        }

 

更新

  /// <summary>
        /// 更新对象部分属性
        /// </summary>
        /// <typeparam name="TEntity"></typeparam>
        /// <param name="predicate"></param>
        /// <param name="updateAction"></param>
        /// <returns></returns>
        public TResult Update(Expression<Func<TEntity, bool>> predicate, Action<TEntity> updateAction)
        {
            List<string> modifyColumns = GetUpdateColumns(updateAction);
            //dbContext.Configuration.AutoDetectChangesEnabled = true;
            var _model = dbContext.Set<TEntity>().AsNoTracking().Where(predicate).ToList();
            if (_model == null) return new TResult(false, "参数为NULL");
            _model.ForEach(p =>
            {
                updateAction(p);
                dbContext.Set<TEntity>().Attach(p);
                var stateEntry = ((IObjectContextAdapter)dbContext).ObjectContext.ObjectStateManager.GetObjectStateEntry(p);
                modifyColumns.ForEach(m => stateEntry.SetModifiedProperty(m));
                //dbContext.Entry<TEntity>(p).State = EntityState.Modified;
            });
            return Save(EntityState.Modified);
        }