ASP.NET Cookbook

10.6. Writing Trace Data to the Event Log with Controllable Levels

Problem

You want your application to output trace information to the event log and, at the same time, control what level of information is output.

Solution

Create your own trace listener that inherits from the TraceListener class and overrides the Write and WriteLine methods to write their output to the event log. A sample trace listener we’ve written to demonstrate this solution is shown in Example 10-20 (VB) and Example 10-21 (C#).

Next, modify your web.config file to add the custom TraceListener and TraceSwitch, as shown in Example 10-22.

In the classes you want to output trace information, create a TraceSwitch object using the name of the TraceSwitch you added to the web.config file, and then use the WriteIf and WriteLineIf methods of the Trace class to output the required messages, as we demonstrate in our class in Example 10-23 (VB) and Example 10-24 (C#).

Discussion

The technique we advocate for writing trace information to the event log involves creating your own custom trace listener that overrides the Write and WriteLine methods and directs their output to the event log. We also find it useful to control the level of messages that are output to the event log, such as outputting only error messages or outputting error and warning messages. Controlling the level of messages that are output involves the use of switches (more about this in a minute).

As discussed in Recipe 10.5, you can add additional listeners to ...