44.4. Tracing

In addition to actively debugging your web applications when things go wrong, you can also implement ASP.NET tracing functionality to look at the information produced in an individual page request. Using tracing enables you to add debug statements to your code that are only viewable when viewing locally; when the web application is deployed to the remote server, users do not see the trace information.

Trace information can include variables and simple objects to help you determine the state of the specific request and how it was executed. Note that ASP.NET tracing is different from using the Trace class in normal Windows applications in that its output is produced on the actual ASP.NET web page or in a stand-alone trace viewer, rather than the output windows that Trace commands use.

44.4.1. Page-Level Tracing

To implement page-level tracing, you simply need to include a trace attribute in the @Page directive at the top of the page you wish to trace. A simple Visual Basic page with tracing activated might look like the following:

<%@ Page Language="vb" Trace="true" AutoEventWireup="false"
   CodeBehind="ShowTrace.aspx.vb" Inherits="DebuggerWebApp.ShowTrace" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
   Transitional//EN" "http://www.w3.org/  TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server"> <title>Trace Example Page</title> </head> <body> <form id="form1" runat="server"> <div>Hello!</div> </form> </body> ...

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