How to use Console.WriteLine in ASP.NET (C#) during debug?

Question

I want to write some result to the console in ASP.NET (C#). It works in a Window application, but a Web application does not work. Here is what I have tried:

Answer 1

Trace.Write("Error Message") and Trace.Warn("Error Message") are the methods to use in web, need to decorate the page header trace=true and in config file to hide the error message text to go to end-user and so as to stay in iis itself for programmer debug.