HttpCompressionModule bug fixed code

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

/// <summary>
/// Implement two way HTTP compression for the SOAP API
/// Code taken from: http://netpl.blogspot.co.uk/2009/07/aspnet-webservices-two-way-response-and.html
/// Fix: Set Content-encoding: gzip header when an Exception occurs on the server.
/// Fix: Do not attempt to decrypt GZIP request stream when request was not GZIPed.
/// </summary>
public class HttpCompressionModule : IHttpModule
{
    private bool isDisposed = false;

    ~HttpCompressionModule()
    {
        Dispose(false);
    }

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

    void context_PreSendRequestHeaders(object sender, EventArgs e)
    {
        // Fix headers having been lost if an exception occurred.
        HttpApplication app = sender as HttpApplication;
        HttpContext ctx = app.Context;
        if (app.Response.Filter is GZipStream) SetEncoding("gzip");
        else if (app.Response.Filter is DeflateStream) SetEncoding("deflate");

        // Fix double header
        if (ctx.Response.Headers["Content-encoding"] == "gzip,gzip")
            ctx.Response.Headers.Set("Content-encoding", "gzip");
    }

    /// <summary>
    /// Fires at the start of each new web request
    /// </summary>
    /// <param name="sender">The Sender</param>
    /// <param name="e">Event Arguments</param>
    public void Context_BeginRequest(object sender, EventArgs e)
    {
        HttpApplication app = sender as HttpApplication;
        HttpContext ctx = app.Context;

        // Currently only enable for the Uploader API webservice
        //if (!ctx.Request.Url.PathAndQuery.ToLower().Contains("uploaderapi.asmx"))
        //{
        //  return;
        //}

        // Add request filter if request was GZIP encoded
        string requestEncoding = ctx.Request.Headers["Content-encoding"];
        if (requestEncoding != null && requestEncoding == "gzip")
        {
           app.Request.Filter =
            new System.IO.Compression.GZipStream(app.Request.Filter, CompressionMode.Decompress);
        }

        // Add response compression filter if the client accepts compressed responses
        if (IsEncodingAccepted("gzip"))
        {
            app.Response.Filter = new GZipStream(app.Response.Filter, CompressionMode.Compress);
            SetEncoding("gzip");
        }
        else if (IsEncodingAccepted("deflate"))
        {
            app.Response.Filter = new DeflateStream(app.Response.Filter, CompressionMode.Compress);
            SetEncoding("deflate");
        }
    }

    private bool IsEncodingAccepted(string encoding)
    {
        return HttpContext.Current.Request.Headers["Accept-encoding"] != null &&
            HttpContext.Current.Request.Headers["Accept-encoding"].Contains(encoding);
    }

    private void SetEncoding(string encoding)
    {
        HttpContext ctx = HttpContext.Current;
        string responseEncodings = ctx.Response.Headers.Get("Content-encoding");
        if (responseEncodings == null || !responseEncodings.Contains(encoding))
            HttpContext.Current.Response.AppendHeader("Content-encoding", encoding);
    }

    public void Dispose()
    {
        Dispose(true);
    }

    private void Dispose(bool dispose)
    {
        isDisposed = dispose;
    }
}