HttpHandler在Asp.net中核心对像之一,我们可以实现IHttpHandler接口来优化Css样式文件. 用一个我们自定义的HttpHandler映射.css的文件.
首先我们最小化Css样式文件尺寸, 然后我们再处理后CSS文件做内存缓存. 缓存依赖物理文件,当文件被修改后,重新加载. 这里我们以Demo为目的,默认
缓存时间2小时. 让我们先来看一下类图是这样的:

我们定义一个IFilesCache的接口,是为了实现两种不能缓存方式.一种是有用System.Web.Caching.Cache,别一个是用.net 4.0下System.Runtime.Caching.ObjectCache的内存Cache. 我们定义一个FilesCacheFactory的类根据.net framework当前版来在创建
当前的实例. 当然你可以直接选择其它组件实现缓存. 下面是Handler的代码:

   1:      /// <summary>   2:      /// MinifyCssHandler    3:      /// </summary>   4:      public class MinifyCssHandler:IHttpHandler   5:      {   6:          private IFilesCache cacheContext;   7:      8:          /// <summary>   9:          /// Initializes a new instance of the <see cref="MinifyCssHandler"/> class.  10:          /// </summary>  11:          public MinifyCssHandler()  12:          {  13:              cacheContext = FilesCacheFactory.GetInstance();  14:          }  15:     16:          #region IHttpHandler Members  17:     18:          /// <summary>  19:          /// Gets a value indicating whether another request can use the <see cref="T:System.Web.IHttpHandler"/> instance.  20:          /// </summary>  21:          /// <returns>true if the <see cref="T:System.Web.IHttpHandler"/> instance is reusable; otherwise, false.</returns>  22:          public bool IsReusable  23:          {  24:              get { return true; }  25:          }  26:     27:          /// <summary>  28:          /// Enables processing of HTTP Web requests by a custom HttpHandler that implements the <see cref="T:System.Web.IHttpHandler"/> interface.  29:          /// </summary>  30:          /// <param name="context">An <see cref="T:System.Web.HttpContext"/> object that provides references to the intrinsic server objects (for example, Request, Response, Session, and Server) used to service HTTP requests.</param>  31:          public void ProcessRequest(HttpContext context)  32:          {  33:              string fileContent = string.Empty;  34:              string filePath = context.Request.PhysicalPath;  35:     36:              string cacheKey = string.Concat("css-", filePath);  37:     38:              object cacheValue = cacheContext.GetFromCache(cacheKey);  39:     40:              if (cacheValue == null)  41:              {  42:                  fileContent = MinifyFiles(filePath);  43:                  cacheContext.AddToCache(cacheKey, fileContent, filePath);  44:              }  45:              else  46:              {  47:                  fileContent = cacheValue as string;  48:              }  49:              context.Response.ContentType = "text/css";  50:              context.Response.Write(fileContent);  51:          }  52:     53:          #endregion  54:     55:          /// <summary>  56:          /// MinifyFiles intent to minfiy css files size  57:          /// </summary>  58:          /// <param name="filePath">css file path</param>  59:          /// <returns>css file of content</returns>  60:          private string MinifyFiles(string filePath)  61:          {  62:              string fileContent = File.ReadAllText(filePath);  63:              fileContent = string.Concat("/* minifyed at ", DateTime.Now, " by Petter Liu */ ", fileContent);  64:              fileContent = Regex.Replace(fileContent, "\t", string.Empty);  65:              fileContent = Regex.Replace(fileContent, "\r\n", string.Empty);  66:              fileContent = Regex.Replace(fileContent, "\r", string.Empty);  67:              fileContent = Regex.Replace(fileContent, "\n", string.Empty);  68:              //Replace more than two spaces  69:              fileContent = Regex.Replace(fileContent, "[ ]{2,}", string.Empty);  70:              return fileContent;  71:          }  72.csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }:      }

与Cache相关的类:

 

        1:      /// <summary>2:      /// IFilesCache   3:      /// </summary>   4:      public interface IFilesCache   5:      {   6:          /// <summary>   7:          /// Add object to cache   8:          /// </summary>   9:          /// <param name="key">key</param>  10:          /// <param name="value">value</param>  11:          /// <param name="filePath">file path</param>  12:          void AddToCache(string key, object value, string filePath);  13:     14:          /// <summary>  15:          /// GetFromCache  16:          /// </summary>  17:          /// <param name="key">key</param>  18:          /// <returns>object</returns>  19:          object GetFromCache(string key);  20:      }  21:     22:      /// <summary>  23:      /// a simple factory create IFilesCache  24:      /// </summary>  25:      public class FilesCacheFactory  26:      {  27:          /// <summary>  28:          /// Create IFilesCache instance  29:          /// </summary>  30:          /// <remarks>System.Runtime.Caching only runtime at .net framework version 4</remarks>  31:          /// <returns>IFilesCache</returns>  32:          public static IFilesCache GetInstance()  33:          {  34:              if (Environment.Version.Major==4)  35:                 return new DotnetRunningCache();  36:              return new WebContextCache();  37:          }  38:     39:      }  40:     41:      public class WebContextCache:IFilesCache  42:      {  43:         #region IFilesCache Members  44:          /// <summary>  45:          /// Add object to cache  46:          /// </summary>  47:          /// <param name="key">key</param>  48:          /// <param name="value">value</param>  49:          /// <param name="filePath">file path</param>  50:          public void  AddToCache(string key, object value, string filePath)  51:          {  52:              //Cache two hour  53:              HttpContext.Current.Cache.Insert(key, value,  54:                                            new CacheDependency(filePath),  55:                                            DateTime.Now.AddHours(2),  56:                                            TimeSpan.Zero);  57:          }  58:     59:          /// <summary>  60:          /// GetFromCache  61:          /// </summary>  62:          /// <param name="key">key</param>  63:          /// <returns>object</returns>  64:          public object GetFromCache(string key)  65:          {  66:              if (string.IsNullOrEmpty(key))  67:                  return new ArgumentNullException("cache key should not null");  68:              return HttpContext.Current.Cache[key];  69:          }  70:     71:          #endregion  72:      }  73:     74:      public class DotnetRunningCache:IFilesCache  75:      {  76:          #region IFilesCache Members  77:          /// <summary>  78:          /// Add object to cache  79:          /// </summary>  80:          /// <param name="key">key</param>  81:          /// <param name="value">value</param>  82:          /// <param name="filePath">file path</param>  83:          public void AddToCache(string key, object value, string filePath)  84:          {  85:               ObjectCache cache = MemoryCache.Default;  86:              var cacheValue = new[] { value };  87:              var cachepolicy = new CacheItemPolicy();  88:              var filespath=new List<string>(){ filePath};  89:              cachepolicy.AbsoluteExpiration = DateTimeOffset.Now.AddHours(2);  90:              cachepolicy.ChangeMonitors.Add(new HostFileChangeMonitor(filespath));  91:     92:              cache.Add(key, cacheValue, cachepolicy);  93:          }  94:     95:          /// <summary>  96:          /// GetFromCache  97:          /// </summary>  98:          /// <param name="key">key</param>  99:          /// <returns>object</returns> 100:          public object GetFromCache(string key) 101:          { 102:              if (string.IsNullOrEmpty(key)) 103:                  return new ArgumentNullException("cache key should not null"); 104:    105:               ObjectCache cache = MemoryCache.Default; 106:              var objects= (Object[])cache.Get(key); 107:              if (objects != null) 108:                  return objects.FirstOrDefault(); 109:              return null; 110:          } 111:    112:          #endregion 113:      }.csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }

在Web.config中增加:

  1:          <httpHandlers>   2:              <add verb="*" path="*.css" validate="false" type="MyWeb.MinifyCssHandler"/>   3:          </httpHandlers>.csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }
  Ok,对比一下,正常情况下是这样:

当增加这个优化Css的HttpHandler后, 是这样的:

有注意size从4.2KB变成了3.2KB. 以上我们直是实现比较简单的,你可以优化实现更高效的算法. 或增加扩展.