.net - Compression in IIS 8.5 not successful, stating ALREADY_CONTENT_ENCODING -

i trying debug issue of why pages not being gzip'ed or deflated according yslow. ended enabling failed request logs on server , able see failed reason of why not compressing, thinks compressed.

dynamic_compression_not_success reason="already_content_encoding" 

i have enabled dynamic , static compression in iis, have changed web.config file include following.

<httpcompression directory="%systemdrive%\inetpub\temp\iis temporary compressed files">   <scheme name="gzip" dll="%windir%\system32\inetsrv\gzip.dll" staticcompressionlevel="9" />   <dynamictypes>     <add mimetype="text/*" enabled="true" />     <add mimetype="message/*" enabled="true" />     <add mimetype="application/x-javascript" enabled="true" />     <add mimetype="application/json" enabled="true" />     <add mimetype="*/*" enabled="false" />   </dynamictypes>   <statictypes>     <add mimetype="text/*" enabled="true" />     <add mimetype="message/*" enabled="true" />     <add mimetype="application/x-javascript" enabled="true" />     <add mimetype="application/atom+xml" enabled="true" />     <add mimetype="application/xaml+xml" enabled="true" />     <add mimetype="*/*" enabled="false" />   </statictypes> </httpcompression> <urlcompression dostaticcompression="true" dodynamiccompression="true"/> 

in addition on aspx page have method call before every page (on page load) run gzip compression (this might why causing error).

this how call method page load

//compress page compression.gzipencodepage(); 

and method compresses page

using system; using system.collections.generic; using system.linq; using system.web;  namespace initialdataentry {     public static class compression     {         /// <summary>         /// sets current page or handler use gzip through response.filter         /// important:           /// have call method before output generated!         /// </summary>         public static void gzipencodepage()         {             httpresponse response = httpcontext.current.response;         if (isgzipsupported())         {             string acceptencoding = httpcontext.current.request.headers["accept-encoding"];             if (acceptencoding.contains("deflate"))             {                 response.filter = new system.io.compression.deflatestream(response.filter,                                            system.io.compression.compressionmode.compress);                 response.appendheader("content-encoding", "deflate");             }             else             {                 response.filter = new system.io.compression.gzipstream(response.filter,                                           system.io.compression.compressionmode.compress);                 response.appendheader("content-encoding", "gzip");             }         }          // allow proxy servers cache encoded , unencoded versions separately         response.appendheader("vary", "content-encoding");     }      /// <summary>     /// determines if gzip supported     /// </summary>     /// <returns></returns>     public static bool isgzipsupported()     {         string acceptencoding = httpcontext.current.request.headers["accept-encoding"];         string ispartial = httpcontext.current.request.headers["x-microsoftajax"];          if (!string.isnullorempty(acceptencoding) &&              acceptencoding.contains("gzip") || acceptencoding.contains("deflate"))              //just checking see if partial page update             if (string.compare("delta=true", ispartial, true) == 0)             {                 return false;             }             else             {                 return true;             }         else         {             return false;         }     } } } 

this used work way, not sure when stopped, users realized issue pages got bloated in size , used 500k 2mb!

any appreciated.

thanks,

we had similar issue on windows 2012 r2 server; following below steps solved our problem:

1. select iis site, , go configuration editor.
2. select "system.web/caching/outputcache" section, set "omitvarystar" property "true"
3. select system.webserver, , select httpcompression.
4. set "staticcompressionignorehitfrequency" property "true"
5. iisreset