Creating a correct absolute URL when running ASP.NET MVC application under Visual Studio Windows Azure Emulator

Question

I need to create an absolute URL to specific files in my ASP.NET MVC 4 application. I am currently doing this by generating a relative path via Url.Content and then using the following extension method to create the absolute path.

public static string Absolute(this UrlHelper url, string relativeUrl)
{
    var request = url.RequestContext.HttpContext.Request;
    return string.Format("{0}://{1}{2}{3}", 
        (request.IsSecureConnection) ? "https" : "http", 
        request.Url.Host, 
        (request.Url.Port == 80) ? "" : ":" + request.Url.Port, 
        VirtualPathUtility.ToAbsolute(relativeUrl));
}

When running under the Azure Emulator, the proper URL that I need to create is http://127.0.0.1/myfile.jpg but when this code executes, the port number comes back as 81 so the URL that is generated is http://127:0.0.1:81/myfile.jpg. However, if I go to http://127:0.0.1:81/myfile.jpg it of course doesn't work as the Azure Emulator is listening on port 80, not 81.

I assume this has to do with the built in Azure Emulator/IIS Express load balancer, but I am not sure what change I need to make to my Url.Absolute method to return an accurate URL.

Answer 1

You can rely on the Host header that is being sent by the client:

public static string Absolute(this UrlHelper url, string relativeUrl)
{
    var request = url.RequestContext.HttpContext.Request;

    return string.Format("{0}://{1}{2}",
        (request.IsSecureConnection) ? "https" : "http",
        request.Headers["Host"],
        VirtualPathUtility.ToAbsolute(relativeUrl));
}

Answer 2

Why not just use @Url.Content("~/myfile.jpg");? This converts a virtual (relative) path to an application absolute path and works finle in IIS,the emulator and when deployed. See UrlHelper.Content Method