关闭的ETag没有服务器

Question

你好，我 刚开始ASP.NET MVC 4和我在一个企业实习谁告诉我没有服务器创建一个基本网店，然后验证HTML和网站的速度与YSlow。

我一直很忙，当我完成了网上商店，我开始使用YSlow的应用速度的网站，但有一件事我似乎无法修复，这是配置错误的ETag：
“有5个具有错误配置ETags的组件“< - 这些是我的CSS文件和我用过的图片。 我一直在研究ETags是什么，仍然不完全知道他们做什么。

我知道Apache可以通过说FileETag none来关闭它们，但是在这种情况下，我没有使用服务器，我仍然想关闭它们，因为它们对分数不满意99.

我在找什么是一个答案什么ETags正好做，并解决我的问题。

感谢

Answer 1

按照以下，这是一个锻炼和显然是一个PC不会是非常高性能的意见。你可以使用httpHandler。这里有一个我使用的图像，将与您的YSlow的帮助（但请注意，这是没有的性能保障，是为指导，以非常繁忙的站点）

public class ImageHandler : IHttpHandler 
    { 
     public void ProcessRequest(HttpContext context) 
     { 
      context.Response.Cache.SetCacheability(HttpCacheability.Public); 
      context.Response.Cache.SetMaxAge(new TimeSpan(28, 0, 0, 0, 0)); 

      // Setting the last modified date to the creation data of the assembly 
     Assembly thisAssembly = Assembly.GetExecutingAssembly(); 
     string thisPath = thisAssembly.CodeBase.Replace(@"file:///", ""); 
     string assemblyName = "yourAssembly"; 
     string assemblyPath = thisPath.Replace(thisAssembly.ManifestModule.ScopeName, assemblyName); 

     var assemblyInfo = new FileInfo(assemblyPath); 
     var creationDate = assemblyInfo.CreationTime; 
     string eTag = GetFileETag(assemblyPath, creationDate);  
     // set cache info 
     context.Response.Cache.SetCacheability(HttpCacheability.Private); 
     context.Response.Cache.VaryByHeaders["If-Modified-Since"] = true; 
     context.Response.Cache.VaryByHeaders["If-None-Match"] = true; 
     context.Response.Cache.SetLastModified(creationDate); 
     context.Response.Cache.SetETag(eTag); 
if (IsFileModified(assemblyPath, creationDate, eTag, context.Request)) 
     { 
      //context.Response.ContentType = <specify content type>; 
      // Do resource processing here 
      context.Response.TransmitFile(context.Request.PhysicalPath); 
     } 
     else 
     { 
      // File hasn't changed, so return HTTP 304 without retrieving the data 
      context.Response.StatusCode = 304; 
      context.Response.StatusDescription = "Not Modified"; 

      // Explicitly set the Content-Length header so the client doesn't wait for 
      // content but keeps the connection open for other requests 
      context.Response.AddHeader("Content-Length", "0");   
     } 


     context.Response.End(); 


     } 


     public bool IsReusable 
     { 
      get { return false; } 
     } 


     /// <summary> 
     /// Checks if the resource assembly has been modified based on creation date. 
     /// </summary> 
     /// <remarks> 
     /// </remarks> 
     /// <seealso cref="GetFileETag"/> 
     private bool IsFileModified(string fileName, DateTime modifyDate, string eTag, HttpRequest request) 
     { 
      // Assume file has been modified unless we can determine otherwise 
      bool FileDateModified = true; 
      DateTime ModifiedSince; 
      TimeSpan ModifyDiff; 
      bool ETagChanged; 

      // Check If-Modified-Since request header, if it exists 
      string ifModifiedSince = request.Headers["If-Modified-Since"]; 
      if (!string.IsNullOrEmpty(ifModifiedSince) && ifModifiedSince.Length > 0 && DateTime.TryParse(ifModifiedSince, out ModifiedSince)) 
      { 
       FileDateModified = false; 
       if (modifyDate > ModifiedSince) 
       { 
        ModifyDiff = modifyDate - ModifiedSince; 
        // Ignore time difference of up to one seconds to compensate for date encoding 
        FileDateModified = ModifyDiff > TimeSpan.FromSeconds(1); 
       } 
      } 
      // Check the If-None-Match header, if it exists. This header is used by FireFox to validate entities based on the ETag response header 
      ETagChanged = false; 
      string ifNoneMatch = request.Headers["If-None-Match"]; 
      if (!string.IsNullOrEmpty(ifNoneMatch) && ifNoneMatch.Length > 0) 
      { 
       ETagChanged = ifNoneMatch != eTag; 
      } 
      return ETagChanged || FileDateModified; 
     } 

     /// <summary> 
     /// Generates a caching ETag based on file name and creation date. 
     /// </summary> 
     /// <remarks> 
     /// </remarks> 
     /// <seealso cref="GetFileETag"/> 
     private string GetFileETag(string fileName, DateTime modifyDate) 
     { 
      string fileString; 
      Encoder stringEncoder; 
      int byteCount; 
      Byte[] stringBytes; 

      // Use file name and modify date as the unique identifier 
      fileString = fileName + modifyDate.ToString(); 

      // Get string bytes 
      stringEncoder = Encoding.UTF8.GetEncoder(); 
      byteCount = stringEncoder.GetByteCount(fileString.ToCharArray(), 0, fileString.Length, true); 
      stringBytes = new Byte[byteCount]; 

      stringEncoder.GetBytes(fileString.ToCharArray(), 0, fileString.Length, stringBytes, 0, true); 

      //{ Hash string using MD5 and return the hex-encoded hash } 
      MD5 Enc = MD5CryptoServiceProvider.Create(); 
      return "\"" + BitConverter.ToString(Enc.ComputeHash(stringBytes)).Replace("-", string.Empty) + "\""; 

     } 
    } 
} 

，然后在你的配置指定处理程序（也可做在httphandlers下如果不使用iis7）

<add name="pngs" verb="*" path="*.png" type="yourAssembly.HttpHandlers.ImageHandler, hcs.web" preCondition="managedHandler" /> 
    <add name="jpgs" verb="*" path="*.jpg" type="yourAssembly.HttpHandlers.ImageHandler, hcs.web" preCondition="managedHandler" /> 
    <add name="gif" verb="*" path="*.gif" type="yourAssembly.HttpHandlers.ImageHandler, hcs.web" preCondition="managedHandler" />