Tracing in ASP.Net

1. To enable tracing for the application, use the element in the Web.config file or machine.config file.
<trace enabled="true" pageOutput="true false" />

2. To enable tracing for a single page, use the attributes of the @Page directive of that page.

<%@ Page Trace="true" Language= ... %>
3. In your code, add custom trace messages where appropriate using the Write and Warn methods of the Trace object.

In Visual Basic .NET:
Trace.Write("Custom Trace", "Beginning User Code...")
Trace.Warn("Custom Trace", "Array count is null!")
In C#:
Trace.Write("Custom Trace", "Beginning User Code...");
Trace.Warn("Custom Trace", "Array count is null!");

Optionally, use the IsEnabled property provided by the current page's TraceContext object (accessed by using the Trace property of the Page object).
In Visual Basic .NET:
If Trace.IsEnabled Then
strMsg = "Tracing is enabled"
Trace.Write("myTrace", strMsg)
End If

In C#:
if (Trace.IsEnabled)
{
strMsg = "Tracing is enabled";
Trace.Write("myTrace", strMsg);
}

View and analyze the trace information. If the pageOutput property was set to true, then trace information will be displayed at the bottom of the Web page. If it was set to false, then it will be displayed in a separate log file, named trace.axd, and located here:
http://ServerName/ApplicationName/trace.axd

DebugGuru