Absolute path back to web-relative path

Question

如果我已设法使用 Server.MapPath 找到并验证文件是否存在，并且我现在想将用户直接发送到该文件，那么将该绝对路径转换回相对 Web 路径的最快方法是什么？

Answer 1

Perhaps this might work:

String RelativePath = AbsolutePath.Replace(Request.ServerVariables["APPL_PHYSICAL_PATH"], String.Empty);

I'm using c# but could be adapted to vb.

Answer 2

Wouldn't it be nice to have Server.RelativePath(path) ?

well, you just need to extend it ;-)

public static class ExtensionMethods
{
    public static string RelativePath(this HttpServerUtility srv, string path, HttpRequest context)
    {
        return path.Replace(context.ServerVariables["APPL_PHYSICAL_PATH"], "~/").Replace(@"\", "/");
    }
}

With this you can simply call

Server.RelativePath(path, Request);

Answer 3

I know this is old but I needed to account for virtual directories (per @Costo's comment). This seems to help:

static string RelativeFromAbsolutePath(string path)
{
    if(HttpContext.Current != null)
    {
        var request = HttpContext.Current.Request;
        var applicationPath = request.PhysicalApplicationPath;
        var virtualDir = request.ApplicationPath;
        virtualDir = virtualDir == "/" ? virtualDir : (virtualDir + "/");
        return path.Replace(applicationPath, virtualDir).Replace(@"\", "/");
    }

    throw new InvalidOperationException("We can only map an absolute back to a relative path if an HttpContext is available.");
}

Answer 4

I like the idea from Canoas. Unfortunately I had not "HttpContext.Current.Request" available (BundleConfig.cs).

I changed the methode like this:

public static string RelativePath(this HttpServerUtility srv, string path)
{
     return path.Replace(HttpContext.Current.Server.MapPath("~/"), "~/").Replace(@"\", "/");
}

Answer 5

If you used Server.MapPath, then you should already have the relative web path. According to the MSDN documentation , this method takes one variable, path , which is the virtual path of the Web server. So if you were able to call the method, you should already have the relative web path immediately accessible.

Answer 6

For asp.net core i wrote helper class to get pathes in both directions.

public class FilePathHelper
{
    private readonly IHostingEnvironment _env;
    public FilePathHelper(IHostingEnvironment env)
    {
        _env = env;
    }
    public string GetVirtualPath(string physicalPath)
    {
        if (physicalPath == null) throw new ArgumentException("physicalPath is null");
        if (!File.Exists(physicalPath)) throw new FileNotFoundException(physicalPath + " doesn't exists");
        var lastWord = _env.WebRootPath.Split("\\").Last();
        int relativePathIndex = physicalPath.IndexOf(lastWord) + lastWord.Length;
        var relativePath = physicalPath.Substring(relativePathIndex);
        return $"/{ relativePath.TrimStart('\\').Replace('\\', '/')}";
    }
    public string GetPhysicalPath(string relativepath)
    {
        if (relativepath == null) throw new ArgumentException("relativepath is null");
        var fileInfo = _env.WebRootFileProvider.GetFileInfo(relativepath);
        if (fileInfo.Exists) return fileInfo.PhysicalPath;
        else throw new FileNotFoundException("file doesn't exists");
    }

from Controller or service inject FilePathHelper and use:

var physicalPath = _fp.GetPhysicalPath("/img/banners/abro.png");

and versa

var virtualPath = _fp.GetVirtualPath(physicalPath);