相同的结果，但稍微干净一点(没有字符串连接/格式化):

public static Uri GetBaseUrl(this UrlHelper url)
{
    Uri contextUri = new Uri(url.RequestContext.HttpContext.Request.Url, url.RequestContext.HttpContext.Request.RawUrl);
    UriBuilder realmUri = new UriBuilder(contextUri) { Path = url.RequestContext.HttpContext.Request.ApplicationPath, Query = null, Fragment = null };
    return realmUri.Uri;
}

public static string ActionAbsolute(this UrlHelper url, string actionName, string controllerName)
{
    return new Uri(GetBaseUrl(url), url.Action(actionName, controllerName)).AbsoluteUri;
}

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

相同的结果，但稍微干净一点(没有字符串连接/格式化):

public static Uri GetBaseUrl(this UrlHelper url)
{
    Uri contextUri = new Uri(url.RequestContext.HttpContext.Request.Url, url.RequestContext.HttpContext.Request.RawUrl);
    UriBuilder realmUri = new UriBuilder(contextUri) { Path = url.RequestContext.HttpContext.Request.ApplicationPath, Query = null, Fragment = null };
    return realmUri.Uri;
}

public static string ActionAbsolute(this UrlHelper url, string actionName, string controllerName)
{
    return new Uri(GetBaseUrl(url), url.Action(actionName, controllerName)).AbsoluteUri;
}

扩展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;
        }
    }
}

然后这样叫它

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

编辑-重新锐化注释

对于已接受的答案，投票最多的评论是这个答案更好，这样Resharper仍然可以验证动作和控制器是否存在。这里有个例子，你可以得到同样的行为。

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;
        }
    }
}

支持信息:

提供智能感知，导航和更多的自定义助手在ASP。NET MVC

Env: dotnet核心版本1.0.4

Url.Action("Join",null, null,Context.Request.IsHttps?"https":"http");

也许这个(?):

<%= 
  Request.Url.GetLeftPart(UriPartial.Authority) + 
  Url.Action("Action1", "Controller2", new {param1="bla", param2="blabla" })
%>