public class CombineFiles : IHttpHandler
{
        private const string CacheKeyFormat = "_CacheKey_{0}_";

 

        private const bool IsCompress = true; //需要壓縮

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }

        public void ProcessRequest(HttpContext context)
        {
            HttpRequest request = context.Request;
            HttpResponse response = context.Response;

            string cachekey = string.Empty;

            string type = request.QueryString["type"];
            if (!string.IsNullOrEmpty(type) && (type == "css" || type == "js"))
            {
                if (type == "js")
                {
                    response.ContentType = "text/javascript";

                }
                else if (type == "css")
                {
                    response.ContentType = "text/css";
                }

                cachekey = string.Format(CacheKeyFormat, type);

                CompressCacheItem cacheItem = HttpRuntime.Cache[cachekey] as CompressCacheItem;
                if (cacheItem == null)
                {
                    string content = string.Empty;
                    string path = context.Server.MapPath("");
                    //找到這個目錄下所有的js或css文件，當然也可以進行配置，需求請求壓縮哪些文件
                    //這里就將所的有文件都請求壓縮
                    string[] files = Directory.GetFiles(path, "*." + type);
                    StringBuilder sb = new StringBuilder();
                    foreach (string fileName in files)
                    {
                        if (File.Exists(fileName))
                        {
                            string readstr = File.ReadAllText(fileName, Encoding.UTF8);
                            sb.Append(readstr);
                        }
                    }

                    content = sb.ToString();

                    // 開始壓縮文件
                    if (IsCompress)
                    {
                        if (type.Equals("js"))
                        {
                            content = JavaScriptCompressor.Compress(content);
                        }
                        else if (type.Equals("css"))
                        {
                            content = CssCompressor.Compress(content);
                        }
                    }

                    //輸入到客戶端還可以進行Gzip壓縮 ,這里就省略了

                    cacheItem = new CompressCacheItem() { Type = type, Content = content, Expires = DateTime.Now.AddDays(30) };
                    HttpRuntime.Cache.Insert(cachekey, cacheItem, null, cacheItem.Expires, TimeSpan.Zero);
                }

                string ifModifiedSince = request.Headers["If-Modified-Since"];
                if (!string.IsNullOrEmpty(ifModifiedSince)
                    && TimeSpan.FromTicks(cacheItem.Expires.Ticks - DateTime.Parse(ifModifiedSince).Ticks).Seconds < 0)
                {
                    response.StatusCode = (int)System.Net.HttpStatusCode.NotModified;
                    response.StatusDescription = "Not Modified";
                }
                else
                {
                    response.Write(cacheItem.Content);
                    SetClientCaching(response, cacheItem.Expires);
                }
            }
        }

        private void SetClientCaching(HttpResponse response, DateTime expires)
        {
            response.Cache.SetETag(DateTime.Now.Ticks.ToString());
            response.Cache.SetLastModified(DateTime.Now);

            //public 以指定響應能由客戶端和共享（代理）緩存進行緩存。    
            response.Cache.SetCacheability(HttpCacheability.Public);

            //是允許文檔在被視為陳舊之前存在的最長絕對時間。 
            response.Cache.SetMaxAge(TimeSpan.FromTicks(expires.Ticks));

            response.Cache.SetSlidingExpiration(true);
        }
        private class CompressCacheItem
        {
            /// <summary>
            /// 類型 js 或 css 
            /// </summary>
            public string Type { get; set; } // js css  
            /// <summary>
            /// 內容
            /// </summary>
            public string Content { set; get; }
            /// <summary>
            /// 過期時間
            /// </summary>
            public DateTime Expires { set; get; }
        }
}

<script type="text/javascript" src="/js/CombineFiles.axd?type=js"></script>
<link rel="stylesheet" type="text/css" href="/css/CombineFiles.axd?type=css" />