How to get full host name + port number in Application_Start of Global.aspx?

I tried

Uri uri = HttpContext.Current.Request.Url;
String host = uri.Scheme + Uri.SchemeDelimiter + uri.Host + ":" + uri.Port;

and it worked well on my local machine, but when being published to IIS7, there is an exception saying

System.Web.HttpException: Request is not available in this context

Anyone know how to achieve this?


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Method 1

When your web application starts, there is no HTTP request being handled.

You may want to handle define the Application_BeginRequest(Object Sender, EventArgs e) method in which the the Request context is available.

Edit: Here is a code sample inspired by the Mike Volodarsky’s blog that Michael Shimmins linked to:

    void Application_BeginRequest(Object source, EventArgs e)
        HttpApplication app = (HttpApplication)source;
        var host = FirstRequestInitialisation.Initialise(app.Context);

    static class FirstRequestInitialisation
        private static string host = null;
        private static Object s_lock = new Object();

        // Initialise only on the first request
        public static string Initialise(HttpContext context)
            if (string.IsNullOrEmpty(host))
                lock (s_lock)
                    if (string.IsNullOrEmpty(host))
                        var uri = context.Request.Url;
                        host = uri.GetLeftPart(UriPartial.Authority);

            return host;

Method 2

The accepted answer is good, but in most cases (if the first request is a HTTP Request) you should better use the Session_Start event, which is called once per user every 20 minutes or so (not sure how long the session is valid). Application_BeginRequest will be fired at every Request.

public void Session_Start(Object source, EventArgs e)
   //Request / Request.Url is available here :)

Method 3

Just answering this so if someone ever decides to actually search on this topic…

This works on application start in any mode…

typeof(HttpContext).GetField("_request", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(HttpContext.Current)

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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