Making Sense of ASP.NET Paths
ASP.Net includes quite a plethora of properties to retrieve path information about
the current request, control and application. There's a ton of information available about paths on
the Request object, some of it appearing to overlap and some of it buried several levels down, and it can be confusing to find just
the right path that you are looking for.
To keep things straight I thought it a good idea to summarize
the path options along with descriptions and example paths. I wrote a post about this a long time ago in 2004 and I find myself frequently going back to that page to quickly figure out which path I’m looking for in processing
the current URL. Apparently a lot of people must be doing
the same, because
the original post is
the second most visited even to this date on this blog to
the tune of nearly 500 hits per day. So, I decided to update and expand a bit on
the original post with a little more information and clarification based on
the original comments.
Request Object Paths Available
Here's a list of
the Path related properties on
the Request object (and
the Page object). Assume a path like http://www.west-wind.com/webstore/admin/paths.aspx for
the paths below where webstore is
the name of
the virtual.
Request Property
Description and Value
ApplicationPath
Returns
the web root-relative logical path to
the virtual root of this app.
/webstore/
PhysicalApplicationPath
Returns local file system path of
the virtual root for this app.
c:\inetpub\wwwroot\webstore
PhysicalPath
Returns
the local file system path to
the current script or path.
c:\inetpub\wwwroot\webstore\admin\paths.aspx
Path
FilePath
CurrentExecutionFilePath
All of these return
the full root relative logical path to
the script page including path and scriptname. CurrentExcecutionFilePath will return
the ‘current’ request path after a Transfer/Execute call while FilePath will always return
the original request’s path.
/webstore/admin/paths.aspx
AppRelativeCurrentExecutionFilePath
Returns an ASP.NET root relative virtual path to
the script or path for
the current request. If in a Transfer/Execute call
the transferred Path is returned.
~/admin/paths.aspx
PathInfo
Returns any extra path following
the script name. If no extra path is provided returns
the root-relative path (returns text in red below). string.Empty if no PathInfo is available.
/webstore/admin/paths.aspx/ExtraPathInfo
RawUrl
Returns
the full root relative URL including querystring and extra path as a string.
/webstore/admin/paths.aspx?sku=wwhelp40
Url
Returns a fully qualified URL including querystring and extra path. Note this is a Uri instance rather than string.
http://www.west-wind.com/webstore/admin/paths.aspx?sku=wwhelp40
UrlReferrer
The fully qualified URL of
the page that sent
the request. This is also a Uri instance and this value is null if
the page was directly accessed by typing into
the address bar or using an HttpClient based Referrer client Http header.
http://www.west-wind.com/webstore/default.aspx?Info
Control.TemplateSourceDirectory
Returns
the logical path to
the folder of
the page, master or user control on which it is called. This is useful if you need to know
the path only to a Page or control from within
the control. For non-file controls this returns
the Page path.
/webstore/admin/
As you can see there’s a ton of information available there for each of
the three common path formats:
Physical Path
is an OS type path that points to a path or file on disk.
Logical Path
is a Web path that is relative to
the Web server’s root. It includes
the virtual plus
the application relative path.
~/ (Root-relative) Path
is an ASP.NET specific path that includes ~/ to indicate
the virtual root Web path. ASP.NET can convert virtual paths into either logical paths using Control.ResolveUrl(), or physical paths using Server.MapPath(). Root relative paths are useful for specifying portable URLs that don’t rely on relative directory structures and very useful from within control or component code.
You should be able to get any necessary format from ASP.NET from just about any path or script using these mechanisms.
~/ Root Relative Paths and ResolveUrl() and ResolveClientUrl()
ASP.NET supports root-relative virtual path syntax in most of its URL properties in Web Forms. So you can easily specify a root relative path in a control rather than a location relative path:
<asp:Image runat="server" ID="imgHelp" ImageUrl="~/images/help.gif" />
ASP.NET internally resolves this URL by using ResolveUrl("~/images/help.gif") to arrive at
the root-relative URL of /webstore/images/help.gif which uses
the Request.ApplicationPath as
the basepath to replace
the ~. By convention any custom Web controls also should use ResolveUrl() on URL properties to provide
the same functionality.
In your own code you can use Page.ResolveUrl() or Control.ResolveUrl() to accomplish
the same thing:
string imgPath = this.ResolveUrl("~/images/help.gif");
imgHelp.ImageUrl = imgPath;
Unfortunately ResolveUrl() is limited to WebForm pages, so if you’re in an HttpHandler or Module it’s not available.
ASP.NET Mvc also has it’s own more generic version of ResolveUrl in Url.Decode:
<script src="<%= Url.Content("~/scripts/new.js") %>" type="text/javascript"></script>
which is part of
the UrlHelper class. In ASP.NET MVC
the above sort of syntax is actually even more crucial than in WebForms due to
the fact that views are not referencing specific pages but rather are often path based which can lead to various variations on how a particular view is referenced.
In a Module or Handler code Control.ResolveUrl() unfortunately is not available which in retrospect seems like an odd design choice – URL resolution really should happen on a Request basis not as part of
the Page framework. Luckily you can also rely on
the static VirtualPathUtility class:
string path = VirtualPathUtility.ToAbsolute("~/admin/paths.aspx");
VirtualPathUtility also many other quite useful methods for dealing with paths and converting between
the various kinds of paths supported. One thing to watch out for is that ToAbsolute() will throw an exception if a query string is provided and doesn’t work on fully qualified URLs. I wrote about this topic with a custom solution that works fully qualified URLs and query strings here (check comments for some interesting discussions too).
Similar to ResolveUrl() is ResolveClientUrl() which creates a fully qualified HTTP path that includes
the protocol and domain name. It’s rare that this full resolution is needed but can be useful in some scenarios.
Mapping Virtual Paths to Physical Paths with Server.MapPath()
If you need to map root relative or current folder relative URLs to physical URLs or you can use HttpContext.Current.Server.MapPath(). Inside of a Page you can do
the following:
string physicalPath = Server.MapPath("~/scripts/ww.jquery.js"));
MapPath is pretty flexible and it understands both ASP.NET style virtual paths as well as plain relative paths, so
the following also works.
string physicalPath = Server.MapPath("scripts/silverlight.js");
as well as dot relative syntax:
string physicalPath = Server.MapPath("../scripts/jquery.js");
Once you have
the physical path you can perform standard System.IO Path and File operations on
the file. Remember with physical paths and IO or copy operations you need to make sure you have permissions to access files and folders based on
the Web server user account that is active (NETWORK SERVICE, ASPNET typically).
Note
the Server.MapPath will not map up beyond
the virtual root of
the application for security reasons.
Server and Host Information
Between these settings you can get all
the information you may need to figure out where you are at and to build new Url if necessary. If you need to build a URL completely from scratch you can get access to information about
the server you are accessing:
Server Variable
Function and Example
SERVER_NAME
The of
the domain or IP Address
wwww.west-wind.com or 127.0.0.1
SERVER_PORT
The port that
the request runs under.
80
SERVER_PORT_SECURE
Determines whether https: was used.
0 or 1
APPL_MD_PATH
ADSI DirectoryServices path to
the virtual root directory. Note that LM typically doesn’t work for ADSI access so you should replace that with LOCALHOST or
the machine’s NetBios name.
/LM/W3SVC/1/ROOT/webstore
Request.Url and Uri Parsing
If you still need more control over
the current request URL or you need to create new URLs from an existing one,
the current Request.Url Uri property offers a lot of control. Using
the Uri class and UriBuilder makes it easy to retrieve parts of a URL and create new URLs based on existing URL.
The UriBuilder class is
the preferred way to create URLs – much preferable over creating URIs via string concatenation.
Uri Property
Function
Scheme
The URL scheme or protocol prefix.
http or https
Port
The port if specifically specified.
DnsSafeHost
The domain name or local host NetBios
machine name
www.west-wind.com or rasnote
LocalPath
The full path of
the URL including script name and extra PathInfo.
/webstore/admin/paths.aspx
Query
The query string if any
?id=1
The Uri class itself is great for retrieving Uri parts, but most of
the properties are read only if you need to modify a URL in order to change it you can use
the UriBuilder class to load up an existing URL and modify it to create a new one.
Here are a few common operations I’ve needed to do to get specific URLs:
Convert
the Request URL to an SSL/HTTPS link
For example to take
the current request URL and converted it to a secure URL can be done like this:
UriBuilder build = new UriBuilder(Request.Url);
build.Scheme = "https";
build.Port = -1; // don't inject portUri newUri = build.Uri;
string newUrl = build.ToString();
Retrieve
the fully qualified URL without a QueryString
AFAIK, there’s no native routine to retrieve
the current request URL without
the query string. It’s easy to do with UriBuilder however:
UriBuilder builder = newUriBuilder(Request.Url);
builder.Query = "";
stringlogicalPathWithoutQuery = builder.ToString();
