Home > Articles > Programming > ASP .NET

Debugging ASP.NET: Tracing

Use ASP.NET's TraceContext class to help you debug your ASP.NET web applications without all the hassle of attempting to use Response.Write on hundreds of lines of code. Read on for tips and techniques for utilizing ASP.NET tracing to its fullest potential.
This chapter is from the book

This chapter is from the book

One of the most common ways to debug traditional ASP web applications is to use trusty calls to Response.Write. This enables you to create checkpoints in your code to view the contents of variables in the browser. This approach had several drawbacks, however. The output created by calls to Response.Write appears wherever the call is made in the code. It sometimes becomes a chore trying to interpret your debugging information because it is strewn all over the page in the browser. The formatting of your page is also affected.

When you are finished debugging your web application using calls to Response.Write, you are then faced with the daunting task of stripping out all this debug code. Because you are using the same type of code both to debug and to create valid output, you must carefully scan each of your ASP pages to make sure that you remove all the Response.Write calls that pertain to debugging. When your ASP pages get to be hundreds of lines long, this can be a real pain.

To address this issue, ASP.NET implements the TraceContext class. The TraceContext class solves all these issues and offers many more features. Let's take a look at some of the ways that the TraceContext class can help you debug your ASP.NET web applications more effectively.


To use tracing in your ASP.NET web application, you need to enable it. This can be done at either the page level or the application level.

Page-Level Configuration

Enabling tracing at the page level entails adding the Trace attribute to the @Page directive, like this:

<%@ Page Language="C#" Trace="true" %>

If the Trace attribute has a value of true, tracing information will be displayed at the bottom of your ASP.NET page after the entire page has been rendered. Alternatively, you can include the TraceMode attribute. The value that you assign to this attribute determines the display order of the trace results. The possible values are SortByTime and SortByCategory. SortByTime is the default if you do not specify the TraceMode attribute.

Application-Level Configuration

Several tracing options are available at the application level. These settings are specified using the <trace> XML element in the <system.web> section of the web.config file. The attributes available to you are shown in Table 6.1.

Table 6.1 Tracing Options


Is true if tracing is enabled for the application; otherwise, is false. The default is false.


Is true if trace information should be displayed both on an application's pages and in the .axd trace utility; otherwise, is false. The default is false. Note that pages that have tracing enabled on them are not affected by this setting.


Specifies the number of trace requests to store on the server. The default is 10.


Indicates whether trace information should be displayed in the order it was processed, SortByTime, or alphabetically by user-defined category, SortByCategory. SortByTime is the default.


Is true if the trace viewer (trace.axd) is available only on the host Web server; otherwise, is false. The default is true.

An example of a trace entry in the web.config file might look like Listing 6.1.

Listing 6.1 Application-Level Trace Configuration in the web.config File

    <trace enabled="true" pageOutput="false"
      traceMode="SortByTime" localOnly="true" />

Even though this example uses all the available attributes, none of them is required. Also note that page-level configuration settings overrule application-level settings. For instance, if tracing is disabled at the application level but is enabled at the page level, trace information will still be displayed in the browser.

The requestLimit attribute sets a limit on how many page requests are kept in the trace log. This prevents the logs from getting too large.

Setting the localOnly attribute to true enables you to view trace information if you are logged into the server locally, but remote users will not see anything. That way, you can enable tracing to debug a problem, and the users of your website will never be the wiser.

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.


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.


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.


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.


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


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


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.


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.


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