MongoDB学习笔记~为IMongoRepository接口更新指定字段

        public void Update<T>(System.Linq.Expressions.Expression<Action<T>> entity) where T : class
        {
            var query = new QueryDocument();
            var fieldList = new List<UpdateDefinition<TEntity>>();

            var param = entity.Body as MemberInitExpression;
            foreach (var item in param.Bindings)
            {
                string propertyName = item.Member.Name;
                object propertyValue;
                var memberAssignment = item as MemberAssignment;
                if (memberAssignment.Expression.NodeType == ExpressionType.Constant)
                {
                    propertyValue = (memberAssignment.Expression as ConstantExpression).Value;
                }
                else
                {
                    propertyValue = Expression.Lambda(memberAssignment.Expression, null).Compile().DynamicInvoke();
                }

                if (propertyName != EntityKey)//更新集中不能有实体键_id
                {
                    fieldList.Add(Builders<TEntity>.Update.Set(propertyName, propertyValue));
                }
                else
                {
                    query = new QueryDocument("_id",new ObjectId(propertyValue.ToString()));
                }

            }

             ForWait(() => _table.UpdateOneAsync(query, Builders<TEntity>.Update.Combine(fieldList)));
        }

        [HttpPost]
        public ActionResult Edit(WebManageUsers entity)
        {
            if (ModelState.IsValid)
            {
                _webManageUsersRepository.Update<WebManageUsers>(i => new WebManageUsers
                {
                    Id = entity.Id,
                    LoginName = entity.LoginName
                });
                return RedirectToAction("Index");
            }
            ModelState.AddModelError("", "请认真填写表单！");
            return View();
        }