点击这里获取更多信息，但基本上不需要扩展方法。它已经存在了，只是不是以非常直观的方式。

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

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

我不确定是否有一个内置的方法来做到这一点，但你可以滚动你自己的HtmlHelper方法。

如下所示

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;
        }
    }
}

然后这样叫它

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

HTHs, 查尔斯

也许这个(?):

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

Env: dotnet核心版本1.0.4

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

使用 @Charlino的回答作为指导，我想出了这个。

ASP。UrlHelper的NET MVC文档显示了Url。如果传入主机名和协议，Action将返回一个完全限定的Url。我创建这些帮助程序是为了强制提供主机名和协议。多重重载反映Url重载。行动:

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);
        }

    }
}