从缓存中读取DataTable

        /// <summary>
        /// 从缓存中读取DataTable
        /// </summary>
        /// <param name="cacheKey">cache key</param>
        /// <param name="strWhere">SQL语句条件</param>
        /// <returns></returns>
        /// <date>
        /// 2009-04-21创建
        /// </date>
        public static DataTable BuildDataTable(string cacheKey, string strWhere)
        {
            DataTable dt=null;
            Cache cache = HttpRuntime.Cache; 
            if (cache[cacheKey] != null)
            {
                dt = (DataTable)cache[cacheKey];
            }
            else
            {
                dt = GetDtFromDataBase(strWhere); 
            }

            cache.Insert(cacheKey, dt, null, DateTime.Now.AddMinutes(30), TimeSpan.Zero);
            return dt;
        }