How do I find the absolute url of an action in ASP.NET MVC?

Click here for more information, but esentially there is no need for extension methods. It's already baked in, just not in a very intuitive way.

Url.Action("Action", null, null, Request.Url.Scheme);

Extend the UrlHelper

namespace System.Web.Mvc
{
    public static class HtmlExtensions
    {
        public static string AbsoluteAction(this UrlHelper url, string action, string controller)
        {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;

            string absoluteAction = string.Format(
                "{0}://{1}{2}",
                requestUrl.Scheme,
                requestUrl.Authority,
                url.Action(action, controller));

            return absoluteAction;
        }
    }
}

Then call it like this

<%= Url.AbsoluteAction("Dashboard", "Account")%>

EDIT - RESHARPER ANNOTATIONS

The most upvoted comment on the accepted answer is This answer is the better one, this way Resharper can still validate that the Action and Controller exists. So here is an example how you could get the same behaviour.

using JetBrains.Annotations

namespace System.Web.Mvc
{
    public static class HtmlExtensions
    {
        public static string AbsoluteAction(
            this UrlHelper url,
            [AspMvcAction]
            string action,
            [AspMvcController]
            string controller)
        {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;

            string absoluteAction = string.Format(
                "{0}://{1}{2}",
                requestUrl.Scheme,
                requestUrl.Authority,
                url.Action(action, controller));

            return absoluteAction;
        }
    }
}

Supporting info:

• Providing Intellisense, Navigation and more for Custom Helpers in ASP.NET MVC

<%= Url.Action("About", "Home", null, Request.Url.Scheme) %>
<%= Url.RouteUrl("Default", new { Action = "About" }, Request.Url.Scheme) %>

Using @Charlino 's answer as a guide, I came up with this.

The ASP.NET MVC documentation for UrlHelper shows that Url.Action will return a fully-qualified Url if a hostname and protocol are passed in. I created these helpers to force the hostname and protocol to be provided. The multiple overloads mirror the overloads for Url.Action:

using System.Web.Routing;

namespace System.Web.Mvc {
    public static class HtmlExtensions {

        public static string AbsoluteAction(this UrlHelper url, string actionName) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, null, (RouteValueDictionary)null, 
                              requestUrl.Scheme, null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            object routeValues) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, null, new RouteValueDictionary(routeValues), 
                              requestUrl.Scheme, null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            RouteValueDictionary routeValues) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, null, routeValues, requestUrl.Scheme, null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            string controllerName) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, controllerName, (RouteValueDictionary)null, 
                              requestUrl.Scheme, null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            string controllerName, 
                                            object routeValues) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, controllerName, 
                              new RouteValueDictionary(routeValues), requestUrl.Scheme, 
                              null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            string controllerName, 
                                            RouteValueDictionary routeValues) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, controllerName, routeValues, requestUrl.Scheme, 
                              null);
        }

        public static string AbsoluteAction(this UrlHelper url, string actionName, 
                                            string controllerName, object routeValues, 
                                            string protocol) {
            Uri requestUrl = url.RequestContext.HttpContext.Request.Url;
            return url.Action(actionName, controllerName, 
                              new RouteValueDictionary(routeValues), protocol, null);
        }

    }
}

I'm not sure if there is a built in way to do it, but you could roll your own HtmlHelper method.

Something like the following

namespace System.Web.Mvc
{
    public static class HtmlExtensions
    {
        public static string AbsoluteAction(this HtmlHelper html, string actionUrl)
        {
            Uri requestUrl = html.ViewContext.HttpContext.Request.Url;

            string absoluteAction = string.Format("{0}://{1}{2}",
                                                  requestUrl.Scheme,
                                                  requestUrl.Authority,
                                                  actionUrl);

            return absoluteAction;
        }
    }
}

Then call it like this

<%= Html.AbsoluteAction(Url.Action("Dashboard", "Account"))%> »

HTHs, Charles