Home > Articles > Programming > ASP .NET

Understanding Paths in ASP.NET

There are more than 30 methods in ASP.NET classes that deal with paths and/or URLs. Many developers coming from traditional ASP tend to stick with the methods they know from ASP (which are still there), but there are many other useful methods that can save you a lot of time and headache. Fritz Onion covers the details of managing paths and URLs in ASP.NET, looking at everything from virtual to physical path mapping to root path reference syntax.
Like this article? We recommend

A quick scan of the classes in the System.Web.* hierarchy reveals more than 30 methods that deal with paths and/or URLs. In this article, I will cover the more commonly used path and URL functions in ASP.NET—presenting what they do, how they work, and when to use them.

The best way to understand what each of these functions and properties do is to try them out and review the results. I have prepared a page that makes calls to the most commonly used path functions and properties in ASP.NET, which you can download from http://staff.develop.com/onion/pathsample.zip. I recommend that you download this file, unzip it, and place the contents in a virtual directory on a machine with ASP.NET installed. Try to access the pathsample.aspx page from a browser, inspect the results, and refer to your running page as you read the rest of this article.

In case you're not near a suitably equipped computer to run the page, Table 1 shows the results of running the test page. This page was run and expressions were all evaluated in the context of a page called client.aspx, responding to a request made to the following URL http://localhost/informit/subdir/pathsample.aspx/extra. The physical directory on the Web server corresponding to this virtual directory mapping was c:\mywebdirs\informit\subdir, and the top-level virtual directory for this application was called informit and was located at c:\mywebdirs\informit.

Table 1 Path Functions in ASP.NET and Their Results

Expression

Evaluation

this.TemplateSourceDirectory

/informit/subdir

Request.MapPath("log.txt")

c:\mywebdirs\informit\subdir\log.txt

this.MapPathSecure("log.txt")

c:\mywebdirs\informit\subdir\log.txt

Request.Path

/informit/subdir/pathsample.aspx/extra

Request.FilePath

/informit/subdir/pathsample.aspx

Request.CurrentExecutionFilePath

/informit/subdir/pathsample.aspx

Request.PathInfo

/extra

Request.PhysicalPath

c:\mywebdirs\informit\subdir\pathsample.aspx

Request.PhysicalApplicationPath

c:\mywebdirs\informit\

Request.ApplicationPath

/informit

Request.Url

http://localhost/informit/subdir/client.aspx/extra

Request.RawUrl

/informit/subdir/pathsample.aspx/extra

Response.ApplyAppPathModifier("foo.aspx")

/informit/subdir/foo.aspx

this.ResolveUrl("~/client.aspx")

/informit/pathsample.aspx


Path Mapping

We start by looking at one of the most commonly used path methods in ASP.NET: MapPath. This useful function converts a virtual path into its corresponding physical path and is typically used to read or modify physical files on the server in the context of a Web request. It is available through the HttpRequest object, and for backward compatibility with classic ASP, it is also available through the HttpServerUtility object (accessed via the HttpContext or Page Server property). As an example of its use, suppose you wanted to write an entry into a log file when a page was accessed. Assuming that the log file is named log.txt and is located in the same directory as the .aspx page that is accessing it, you could write to the file with the following code:

// within a method of the Page class
string logfile = Request.MapPath("log.txt");
using (StreamWriter sw = File.AppendText(logfile))
{
 sw.WriteLine("I was here at {0}", DateTime.Now);
}

Notice in Table 1 that the call to MapPath with a string of log.txt resulted in the complete path c:\mywebdirs\informit\subdir\log.txt corresponding to the physical location of the virtual directory accessed in the request. In general, any time you call MapPath, it prefixes the string you pass in with the complete physical directory path to the current directory to which the request was dispatched. This is useful any time you need to access a physical file on disk that is placed in the same directory as your page, particularly for things such as loading XML files, writing to log files, and performing file manipulation.

Be aware that any time you access the file system from within an ASP.NET application, you are operating under the restrictive rights associated with the ASPNET account (or, in Windows Server 2003, NETWORK SERVICE). This account is specially created for ASP.NET on your machine, and by default is granted only User privileges. In a typical installation, this means that you cannot modify existing or create new files from within an ASP.NET page. If you find yourself wanting to use MapPath to modify or create files, the best solution is to grant the ASP.NET account write and modify privileges to that one subdirectory.

There is an additional function for performing virtual to physical path mapping in ASP.NET called MapPathSecure. This method, also of the HttpRequest class, differs only in the fact that it makes a File I/O security demand as you request the translation, but it is used internally in many of the ASP.NET methods. This demand is not the same as requesting whether the account has privileges to write to a file, but rather whether the code that is currently being executed has sufficient trust to perform file I/O (done through a code access security or CAS check). Most of the time, your ASP.NET code will be running with full privileges, so this function will always succeed. It is possible, however, in ASP.NET 1.1 to specify a lower trust level at which to run your application using the trust element in your configuration file (or more likely, for some third-party host environment to run your application at a lower level of trust). If this is a possibility for you, then it may make sense to call MapPathSecure instead of MapPath, as it will trigger a code access security exception sooner rather than later, giving your more flexibility in dealing with the failure.

There are two other potentially useful properties available in the Request object: PhysicalPath and PhysicalApplicationPath. The former is the complete physical path to the endpoint that was requested, and the latter is the complete physical path to the root of the application.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020