Fixed AppHarbor Module

AppHarborModule.cs

using System;
using System.Collections.Specialized;
using System.Configuration;
using System.Linq.Expressions;
using System.Reflection;
using System.Web;

namespace SLaks {
	//Based on: https://github.com/trilobyte/Premotion-AspNet-AppHarbor-Integration/blob/master/src/Premotion.AspNet.AppHarbor.Integration/AppHarborIntegrationModule.cs

	/// <summary>
	/// This module modifies the native <see cref="T:System.Web.HttpContext"/> to hide the AppHarbor load balancing setup from ASP.Net.
	/// </summary>
	/// <remarks>
	/// This should take care of the following issues:
	/// http://support.appharbor.com/kb/getting-started/workaround-for-generating-absolute-urls-without-port-number
	/// http://support.appharbor.com/kb/getting-started/information-about-our-load-balancer
	/// </remarks>
	public class AppHarborModule : IHttpModule {
		#region Constants
		/// <summary>
		/// Defines the name of the setting which to use to detect AppHarbor.
		/// </summary>
		private const string AppHarborDetectionSettingKey = "appharbor.commit_id";
		/// <summary>
		/// AppHarbor uses a load balancer which rewrites the REMOTE_ADDR header. 
		/// The original user's IP addres is stored in a separate header with this name.
		/// </summary>
		private const string ForwardedForHeaderName = "HTTP_X_FORWARDED_FOR";
		/// <summary>
		/// AppHarbor uses a load balancer which rewrites the SERVER_PROTOCOL header. 
		/// The original protocol is stored in a separate header with this name.
		/// </summary>
		/// <remarks>http://en.wikipedia.org/wiki/X-Forwarded-For</remarks>
		private const string ForwardedProtocolHeaderName = "HTTP_X_FORWARDED_PROTO";
		/// <summary>
		/// Defines the separator which to use to split the Forwarded for header.
		/// </summary>
		/// <remarks>http://en.wikipedia.org/wiki/X-Forwarded-For</remarks>
		private const string ForwardedForAddressesSeparator = ", ";
		#endregion

		#region Implementation of IHttpModule
		/// <summary>
		/// Initializes a module and prepares it to handle requests.
		/// </summary>
		/// <param name="context">An <see cref="T:System.Web.HttpApplication"/> that provides access to the methods, properties, and events common to all application objects within an ASP.NET application </param>
		public void Init(HttpApplication context) {
			//If we're not running on AppHarbor, do nothing.
			var appHarborCommitId = ConfigurationManager.AppSettings[AppHarborDetectionSettingKey];
			if (string.IsNullOrEmpty(appHarborCommitId))
				return;

			var collectionType = typeof(NameValueCollection);
			var readOnlyProperty = collectionType.GetProperty("IsReadOnly", BindingFlags.NonPublic | BindingFlags.Instance);
			if (readOnlyProperty == null)
				throw new InvalidOperationException(string.Format("Could not find property '{0}' on type '{1}'", "IsReadOnly", collectionType));

			var collectionParam = Expression.Parameter(typeof(NameValueCollection));

			var isReadOnly = Expression.Lambda<Func<NameValueCollection, bool>>(
				Expression.Property(collectionParam, readOnlyProperty),
				collectionParam
			).Compile();

			var valueParam = Expression.Parameter(typeof(bool));
			var setReadOnly = Expression.Lambda<Action<NameValueCollection, bool>>(
				Expression.Call(collectionParam, readOnlyProperty.GetSetMethod(nonPublic: true), valueParam),
				collectionParam, valueParam
			).Compile();

			// listen to incoming requests to modify
			context.BeginRequest += (sender, args) => {
				// get the http context
				var serverVariables = HttpContext.Current.Request.ServerVariables;

				// get the forwarder headers
				var forwardedFor = serverVariables[ForwardedForHeaderName] ?? string.Empty;
				var protocol = serverVariables[ForwardedProtocolHeaderName] ?? string.Empty;
				var isHttps = "HTTPS".Equals(protocol, StringComparison.OrdinalIgnoreCase);

				bool wasReadOnly = isReadOnly(serverVariables);
				if (wasReadOnly)
					setReadOnly(serverVariables, false);

				// split the forwarded for header by comma+space separated list of IP addresses, the left-most being the farthest downstream client
				// see http://en.wikipedia.org/wiki/X-Forwarded-For
				var forwardSeparatorIndex = forwardedFor.IndexOf(ForwardedForAddressesSeparator);
				if (forwardSeparatorIndex > 0)
					serverVariables.Set("REMOTE_ADDR", forwardedFor.Remove(forwardSeparatorIndex));

				// set correct headers
				serverVariables.Set("HTTPS", isHttps ? "on" : "off");
				serverVariables.Set("SERVER_PORT", isHttps ? "443" : "80");
				serverVariables.Set("SERVER_PORT_SECURE", isHttps ? "1" : "0");

				if (wasReadOnly)
					setReadOnly(serverVariables, true);
			};
		}
		/// <summary>
		/// Disposes of the resources (other than memory) used by the module that implements <see cref="T:System.Web.IHttpModule"/>.
		/// </summary>
		public void Dispose() { }		// nothing to do here
		#endregion
	}
}

Fixed in version 0.2.0, thanks for reporting!

So should I use this or @TriloByte 's?

@Korayem: Use @TriloByte's; this issue was fixed. You can grab it from NuGet.

Perfect, thanks :)

Do you know if there is a way to get the remote user agent this way as well?

Nevermind my previous question, it was there all along