Beginning ASP.NET 4.5 in CSharp and VB Opsylum

Tracing Your ASP.NET Web Pages x 723
Adding Your Own Information to the Trace
Adding your own data to the trace is useful if, for example, you want to see the value of a variable,
or want to find out if a specific event fires, and when it fires exactly.
You can add information to the trace by using the Trace class. This class exposes two useful methods:
Write and Warn. Both do pretty much the same thing: they add information to the trace that
you can optionally put in a category you make up yourself. The only difference between Write and
Warn is that messages written by Warn appear in red. You could use the Warn method for unexpected
situations because the message will draw more attention.
In the following exercise, you see how simple it is to add your own information to the trace using
the Warn and Write methods.
TRY IT OUT
Adding Trace Data to Your Pages
In this Try It Out, you add some custom information to the ASP.NET trace. You use the Write method
to write out trace information in a normal page execution, and use the Warn method for unexpected
scenarios.
1. Open CalculatorDemo.aspx, switch to its Code Behind, and locate the Click handler for the
Calculate button.
2. Right before the Select Case (VB.NET) or switch statement (C#), add the following Trace
.Write call:
VB.NET
Trace.Write(String.Format("Performing the calculation with the {0} operator",
OperatorList.SelectedValue))
Select Case OperatorList.SelectedValue
C#
Trace.Write(string.Format("Performing the calculation with the {0} operator",
OperatorList.SelectedValue));
switch (OperatorList.SelectedValue)
3. Near the bottom of the event handler, modify the Else statement for the check that ensures that
both TextBox controls contain a value:
VB.NET
Else
Result.Text = String.Empty
Trace.Warn("Custom Category",
"TextBox controls are empty; time to add Validation controls?")
End If
C#
else
{