GZipping all content served up by ASP.NET

Update – I now realise this post is kind of pointless, there is a module for compression of dynamic content, called unsurprisingly DynamicCompressionModule… But the approach described may be useful for someone somewhere…

I couldn’t find anything that will GZip all the content returned by ASP.NET. There’s a module for compression of static files but nothing for dynamic content. There may be a good reason for this, perhaps the overhead of GZipping content on the fly can kill your server, but since my current project has no static content I thought it would be useful to give it a go. The solution is pretty simple, register the following module in web.config and you’re good to go.

using System;
using System.IO.Compression;
using System.Web;

namespace MyNamespace
{
  public class GzipModule : IHttpModule
  {
    public void Dispose()
    {
      
    }

    public void Init(HttpApplication context)
    {
      context.BeginRequest += new EventHandler(context_BeginRequest);
    }

    void context_BeginRequest(object sender, EventArgs e)
    {
      HttpApplication app = (HttpApplication)sender;
      if ((app.Request.Headers["Accept-Encoding"] != null) &&
            (app.Request.Headers["Accept-Encoding"].Contains("gzip")))
      {
        app.Response.Filter = new GZipStream(app.Response.Filter, CompressionMode.Compress);
        app.Response.AppendHeader("Content-encoding", "gzip");
        app.Response.Cache.VaryByHeaders["Accept-encoding"] = true;
      }
    }
  }
}

Registration is as follows

    <modules>
            <add name="GzipModule" type="MyNamespace.GzipModule" />
    </modules>