This should answer your questions. I got it from the help files in VS.Net.
Trace Class [Visual Basic]
Provides a set of methods and properties that help you trace the execution
of your code. This class cannot be inherited.
For a list of all members of this type, see Trace Members.
System.Object
System.Diagnostics.Trace
[Visual Basic]
NotInheritable Public Class Trace
[C#]
public sealed class Trace
[C++]
public __gc __sealed class Trace
[JScript]
public class Trace
Thread Safety
This type is safe for multithreaded operations.
Remarks
You can use the properties and methods in the Trace class to instrument
release builds. Instrumentation allows you to monitor the health of your
application running in real-life settings. Tracing helps you isolate problems
and fix them without disturbing a running system.
Note To enable debugging in C#, add the /d:TRACE flag to the compiler
command line when you compile your code, or you can add #define TRACE to the
top of your file. In Visual Basic, add the /d:TRACE=True flag to the compiler
command line. To provide equivalent funtionality in the Managed Extensions
for C++, you must enclose calls to methods of this class in a #ifdef TRACE
.... #endif block. This syntax is compiler-specific. If you are using a
compiler other than the ones specified above, you must refer to the
compiler's documentation to enable conditional compiling because of the
conditional compilation attributes placed on the methods of the Trace class.
In Visual Studio .NET projects, Trace is enabled by default. Therefore, code
is generated for all Trace methods in both release and debug builds. This
allows an end user to turn on tracing to help identify the problem without
the program having to be recompiled. By contrast, Debug is disabled in
release builds by default, so no executable code is generated for Debug
methods. To disable Trace, see the Visual Studio .NET documentation.
This class provides methods to display an Assert dialog box, and to emit an
assertion that will always Fail. This class provides write methods in the
following variations: Write, WriteLine, WriteIf, and WriteLineIf.
The BooleanSwitch and TraceSwitch classes provide means to dynamically
control the tracing output. You can modify the values of these switches
without recompiling your application. For information on using the
configuration file to set a switch, see the Switch class and TraceSwitch
Configuration topic in the Visual Studio .NET documentation.
You can customize the tracing output's target by adding TraceListener
instances to or removing instances from the Listeners collection. By default,
trace output is emitted using the DefaultTraceListener class.
The Trace class provides properties to get or set the level of Indent, the
IndentSize, and whether to AutoFlush after each write.
To set the AutoFlush and IndentSize for Trace, you can edit the
configuration file that corresponds to the name of your application. The
configuration file should be formatted like the following example:
<configuration>
<system.diagnostics>
<trace autoflush="false" indentsize="3" />
</system.diagnostics>
</configuration>
Example
The following example uses Trace to indicate the beginning and the end of a
program's execution. The example also uses Indent and Unindent to distinguish
the tracing output.
[Visual Basic]
Public Shared Sub Main()
Trace.Listeners.Add(New TextWriterTraceListener(Console.Out))
Trace.AutoFlush = True
Trace.Indent()
Trace.WriteLine("Entering Main")
Console.WriteLine("Hello World.")
Trace.WriteLine("Exiting Main")
Trace.Unindent()
End Sub 'Main
