Get subdomain in c# asp.net.cs

protected override void Initialize(RequestContext requestContext)
{
    base.Initialize(requestContext);
    string domain = Dns.GetHostEntry(this.Request.UserHostName).HostName;
    string[] segments = domain.Split('.');
    string subdomain = "";

    if(segments.Length >= 3)
    {
        subdomain = segments[0];
        if(subdomain != "www")
        {
            Session["company_entry"] = subdomain;
        }
    }
}