Getting Absolute URL from an ASP.NET MVC Action

This probably is a dummy question but I cannot find a clear indication. I have a POCO class in a MVC3 web application whose only purpose is managing the backup of some files in the server. Typically it creates a backup and returns the filename to the controller, which sends an email with the URL for downloading it. This works fine, but I cannot build the absolute URL to be sent. No matter which function I use, I always get a relative URL, like /Backup/TheFile.zip, rather than e.g. http://www.somesite.com/Backup/TheFile.zip. I tried:

VirtualPathUtility.ToAbsolute("~/Backup/SomeFile.zip");
HttpRuntime.AppDomainAppVirtualPath + "/Backup/SomeFile.zip";
Url.Content("~/Backup/SomeFile.zip");

but they all return something like /Backup/SomeFile.zip. Any idea?

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You have a few options:

  • Save the value of HttpContext.Request.Url in a static or member variable, and use that to pass the Fully-qualified path.
  • Save the app domain in an app setting in the web.config.
  • Hard-code the value.
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最佳答案

You can do it by the following:

var urlBuilder =
new System.UriBuilder(Request.Url.AbsoluteUri)
{
Path = Url.Action("Action", "Controller"),
Query = null,
};


Uri uri = urlBuilder.Uri;
string url = urlBuilder.ToString();
// or urlBuilder.Uri.ToString()

Instead of Url.Action() in this sample, you can also use Url.Content(), or any routing method, or really just pass a path.

But if the URL does go to a Controller Action, there is a more compact way:

var contactUsUriString =
Url.Action("Contact-Us", "About",
routeValues: null /* specify if needed */,
protocol: Request.Url.Scheme /* This is the trick */);

The trick here is that once you specify the protocol/scheme when calling any routing method, you get an absolute URL. I recommend this one when possible, but you also have the more generic way in the first example in case you need it.

I have blogged about it in details here:
http://gurustop.net/blog/2012/03/23/writing-absolute-urls-to-other-actions-in-asp-net-mvc/

Extracted from Meligy’s AngularJS & Web Dev Goodies Newsletter

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From within the controller:

var path = VirtualPathUtility.ToAbsolute(pathFromPoco);
var url = new Uri(Request.Url, path).AbsoluteUri
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The built-in helpers in MVC 4 create absolute URLs if either the host or protocol parameters are non-empty. See this answer here with an example extension method for use in views.

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This works for me:

using System;
using System.Web;
using System.Web.Mvc;


public static class UrlExtensions
{
public static string Content(this UrlHelper urlHelper, string contentPath, bool toAbsolute = false)
{
var path = urlHelper.Content(contentPath);
var url = new Uri(HttpContext.Current.Request.Url, path);


return toAbsolute ? url.AbsoluteUri : path;
}
}

Usage in cshtml:

@Url.Content("~/Scripts/flot/jquery.flot.menuBar.js", true)
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I wrote a helper class for this, for MVC 5... It's pretty flexible, and is particularly useful if you need this functionality when you aren't inside a controller. You should be able to drop it right into a project and go.

As Meligy pointed out, the key is to include the protocol. Here I have it hard coded as http, so if you want to use SSL that might need to become a bit more flexible. 

public class AbsoluteUrlHelper
{
/// <summary>
/// Creates an absolute "fully qualified" url from an action, and assumes the current controller.
/// </summary>
/// <returns></returns>
public static string GetAbsoluteUrl(string action, object routeValues = null)
{
var urlHelper = new UrlHelper(HttpContext.Current.Request.RequestContext);
var values = urlHelper.RequestContext.RouteData.Values;
var controller = values["controller"].ToString();


return GetAbsoluteUrl(action, controller, urlHelper, routeValues);
}


/// <summary>
/// Creates an absolute "fully qualified" url from an action and controller.
/// </summary>
public static string GetAbsoluteUrl(string action, string controller, object routeValues = null)
{
var urlHelper = new UrlHelper(HttpContext.Current.Request.RequestContext);


return GetAbsoluteUrl(action, controller, urlHelper, routeValues);
}


/// <summary>
/// Creates an absolute "fully qualified" url from an action and controller.
/// </summary>
public static string GetAbsoluteUrl(string action, string controller, UrlHelper urlHelper, object routeValues = null)
{
var uri = urlHelper.Action(action, controller, routeValues, "http");


return uri;
}
}
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In ASP.Net Core 2.0 (MVC) this works to create an absolute url to an action.

var url = Url.Action("About", "Home", new { /*Route values here*/ }, Request.Scheme);

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