/// <summary>
        /// 等待Task执行完成后再返回
        /// </summary>
        /// <param name="func"></param>
        /// <returns></returns>
        private Task ForWait(Func<Task> func)
        {
            var t = func();
            t.Wait();
            return t;
        }

       public Task InsertAsync(TEntity item)
        {
            return ForWait(() => _table.InsertOneAsync(item));
        }

        public Task DeleteAsync(TEntity item)
        {
            var query = new QueryDocument("_id", new ObjectId(typeof(TEntity).GetProperty(EntityKey).GetValue(item).ToString()));
            return ForWait(() => _table.DeleteOneAsync(query));

        }

        public Task UpdateAsync(TEntity item)
        {

            var query = new QueryDocument("_id", new ObjectId(typeof(TEntity).GetProperty(EntityKey).GetValue(item).ToString()));
            var fieldList = new List<UpdateDefinition<TEntity>>();
            foreach (var property in typeof(TEntity).GetProperties(BindingFlags.Instance | BindingFlags.Public))
            {
                if (property.Name != EntityKey)//更新集中不能有实体键_id
                {
                    fieldList.Add(Builders<TEntity>.Update.Set(property.Name, property.GetValue(item)));
                }
            }

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

        }

       public void Insert(TEntity item)
        {
            InsertAsync(item);
        }

        public void Delete(TEntity item)
        {
            DeleteAsync(item);
        }

        public void Update(TEntity item)
        {
            UpdateAsync(item);
        }