HttpRequestMessage.GetClientIpAddress for ASP.NET MVC 4 / Web API

HttpRequestMessageHelper.cs

// Original idea: http://stackoverflow.com/questions/9565889/get-the-ip-address-of-the-remote-host

using System.Net.Http;
using System.ServiceModel.Channels;
using System.Web;

namespace CrowSoftware.Api
{
    public static class HttpRequestMessageHelper
    {
        public static string GetClientIpAddress(this HttpRequestMessage request)
        {
            if (request.Properties.ContainsKey("MS_HttpContext"))
            {
                return ((HttpContextWrapper)request.Properties["MS_HttpContext"]).Request.UserHostAddress;
            }
            else if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
            {
                RemoteEndpointMessageProperty prop;
                prop = (RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name];
                return prop.Address;
            }
            else
            {
                return null;
            }
        }
    }
}

Very nice, but it could be a little cleaner:

public static string GetClientIpAddress(this HttpRequestMessage request)
{
    if (request.Properties.ContainsKey("MS_HttpContext"))
        return ((HttpContextWrapper)request.Properties["MS_HttpContext"]).Request.UserHostAddress;

    if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
        return ((RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name]).Address;

    return "IP Address Unavailable";    //here the user can return whatever they like
}

I'd add one more change:

Instead of Casting to HttpContextWrapper which is not easy to Mock cast to HttpContextBase:

public static string GetClientIpAddress(this HttpRequestMessage request)
{
if (request.Properties.ContainsKey("MS_HttpContext"))
return ((HttpContextBase)request.Properties["MS_HttpContext"]).Request.UserHostAddress;

if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
    return ((RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name]).Address;

return "IP Address Unavailable";    //here the user can return whatever they like

}

Another change which may be considered useful is to return type IPAddress instead of string.

    public static IPAddress GetClientIpAddress(this HttpRequestMessage request)
    {
        if (request.Properties.ContainsKey("MS_HttpContext"))
        {
            return IPAddress.Parse(((HttpContextBase)request.Properties["MS_HttpContext"]).Request.UserHostAddress);
        }
        if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
        {
            return IPAddress.Parse(((RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name]).Address);
        }
        throw new Exception("Client IP Address Not Found in HttpRequest");
    }

Another change with support for OWIN

public static IPAddress GetClientIpAddress(this HttpRequestMessage request)
{
    if (request.Properties.ContainsKey("MS_HttpContext"))
    {
        return IPAddress.Parse(((HttpContextBase)request.Properties["MS_HttpContext"]).Request.UserHostAddress);
    }

    if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
    {
        return IPAddress.Parse(((RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name]).Address);
    }

    if (request.Properties.ContainsKey("MS_OwinContext"))
    {
        return IPAddress.Parse(((OwinContext)request.Properties["MS_OwinContext"]).Request.RemoteIpAddress);
    }

    throw new Exception("Client IP Address Not Found in HttpRequest");
}

UserHostName '((((HttpContextBase)request.Properties["MS_HttpContext"])).Request).UserHostName' threw an exception of type 'System.ArgumentException' string {System.ArgumentException}

UserHostName '((((HttpContextBase)request.Properties["MS_HttpContext"])).Request).UserHostName' threw an exception of type 'System.ArgumentException' string {System.ArgumentException}

I'm having same problem with Argument exception. It happens when I wrap the code in Task.Run(... )