ASP.NET 3.5 For Dummies®

20.9. Tracing the (Mis)Steps of a Web Page

Tracing is collecting information about an ASP.NET page or application while it runs. You trace data to investigate problems and slow performance in a production site. ASP.NET raises numerous events while it runs. When trace is on, details about those events appear in the trace log.

In this section, you add your trace information to the trace log.

20.9.1. Implementing trace in a page

You trace a single page or all the pages in a Web site.

To trace a single page, open the ASP.NET page in Source view and change the Page directive to include two additional attributes:

<%@ Page Language="VB"
  TraceMode="SortByCategory"
Trace="true" %>

Run the page. ASP.NET inserts rows and columns of information about what happened, when it happened, and what the values were. The control tree category is especially useful. The grid describes the controls on the page and shows where they fit inside their parent containers. For example, Figure 20-13 shows lblText, ddl, and btnOK inside form1 (where they belong).

Check the ViewState Size column if an ASP.NET page seems sluggish and bloated. In many cases, you can put a control on a diet by setting its EnableViewState property to false.

Figure 20-13. Part of the control tree.

Don't leave tracing on in a production ...