How do I convert a file path to a URL in ASP.NET

问题:

Basically I have some code to check a specific directory to see if an image is there and if so I want to assign a URL to the image to an ImageControl.

if (System.IO.Directory.Exists(photosLocation))
{
    string[] files = System.IO.Directory.GetFiles(photosLocation, "*.jpg");
    if (files.Length > 0)
    {
        // TODO: return the url of the first file found;
    }
}

回答1:

As far as I know, there's no method to do what you want; at least not directly. I'd store the photosLocation as a path relative to the application; for example: "~/Images/". This way, you could use MapPath to get the physical location, and ResolveUrl to get the URL (with a bit of help from System.IO.Path):

string photosLocationPath = HttpContext.Current.Server.MapPath(photosLocation);
if (Directory.Exists(photosLocationPath))
{
    string[] files = Directory.GetFiles(photosLocationPath, "*.jpg");
    if (files.Length > 0)
    {
        string filenameRelative = photosLocation +  Path.GetFilename(files[0])   
        return Page.ResolveUrl(filenameRelative);
    }
}

回答2:

this is what i use:

private string MapURL(string path)
{
    string appPath = Server.MapPath("/").ToLower();
    return string.Format("/{0}", path.ToLower().Replace(appPath, "").Replace(@"\", "/"));
 }

回答3:

The problem with all these answers is that they do not take virtual directories into account.

Consider:

Site named "tempuri.com/" rooted at c:\domains\site
virtual directory "~/files" at c:\data\files
virtual directory "~/files/vip" at c:\data\VIPcust\files

So:

Server.MapPath("~/files/vip/readme.txt") 
  = "c:\data\VIPcust\files\readme.txt"

But there is no way to do this:

MagicResolve("c:\data\VIPcust\files\readme.txt") 
   = "http://tempuri.com/files/vip/readme.txt"

because there is no way to get a complete list of virtual directories.

回答4:

I've accepted Fredriks answer as it appears to solve the problem with the least amount of effort however the Request object doesn't appear to conatin the ResolveUrl method. This can be accessed through the Page object or an Image control object:

myImage.ImageUrl = Page.ResolveUrl(photoURL);
myImage.ImageUrl = myImage.ResolveUrl(photoURL);

An alternative, if you are using a static class as I am, is to use the VirtualPathUtility:

myImage.ImageUrl = VirtualPathUtility.ToAbsolute(photoURL);

回答5:

Maybe this is not the best way, but it works.

// Here is your path
String p = photosLocation + "whatever.jpg";

// Here is the page address
String pa = Page.Request.Url.AbsoluteUri;

// Take the page name    
String pn = Page.Request.Url.LocalPath;

// Here is the server address    
String sa = pa.Replace(pn, "");

// Take the physical location of the page    
String pl = Page.Request.PhysicalPath;

// Replace the backslash with slash in your path    
pl = pl.Replace("\\", "/");    
p = p.Replace("\\", "/");

// Root path     
String rp = pl.Replace(pn, "");

// Take out same path    
String final = p.Replace(rp, "");

// So your picture's address is    
String path = sa + final;

Edit: Ok, somebody marked as not helpful. Some explanation: take the physical path of the current page, split it into two parts: server and directory (like c:\inetpub\whatever.com\whatever) and page name (like /Whatever.aspx). The image's physical path should contain the server's path, so "substract" them, leaving only the image's path relative to the server's (like: \design\picture.jpg). Replace the backslashes with slashes and append it to the server's url.

回答6:

This worked for me:

HttpContext.Current.Request.Url.GetLeftPart(UriPartial.Authority) + HttpRuntime.AppDomainAppVirtualPath + "ImageName";

回答7:

So far as I know there's no single function which does this (maybe you were looking for the inverse of MapPath?). I'd love to know if such a function exists. Until then, I would just take the filename(s) returned by GetFiles, remove the path, and prepend the URL root. This can be done generically.

回答8:

The simple solution seems to be to have a temporary location within the website that you can access easily with URL and then you can move files to the physical location when you need to save them.

回答9:

For get the left part of the URL:

?HttpContext.Current.Request.Url.GetLeftPart(UriPartial.Authority)
"http://localhost:1714"

For get the application (web) name:

?HttpRuntime.AppDomainAppVirtualPath
"/"

With this, you are available to add your relative path after that obtaining the complete URL.

回答10:

I think this should work. It might be off on the slashes. Not sure if they are needed or not.

string url = Request.ApplicationPath + "/" + photosLocation + "/" + files[0];