Chapter 6: Debugging and Tracing Threads

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Overview

Debugging and tracing are two techniques frequently, and often necessarily, employed by developers. The former allows a developer to analyze an application's variables and code, and step through the program's code flow. The latter allows us to trace the behavior of our application, displaying information in a listener (a log file, the Windows event log, or similar). They are fundamental to creating robust applications because they provide an easy way to monitor and understand how our application is working. The big difference between the two techniques is that tracing can be done during an application's run time, while the debugger is used at design time, before releasing the final version of our application.

Desktop application developers have traditionally had access to excellent debugging support, with the ability to use breakpoints and examine the contents of variables. .NET is no exception in this regard, but the issues inherent in using breakpoints in a multithreaded application deserve some attention, and will be the focus of this chapter.

Outside the desktop, developers have long suffered from the lack of a good debugger for web applications written in environments such as ASP. In order to understand a variable's value, or the code's flow, and every common task usually done with a debugger, ASP developers often had to populate their code with Response.Write() statements, echoing messages like Entered the function, Exited from the loop, and so on. Then when they had finished testing the ASP application, they needed to remove all the undesired statements. That's not the best way to debug a program.

Fortunately, .NET brings debugging functionality to the next generation of ASP developers by providing four useful classes: Trace, Debug, BooleanSwitch, and TraceSwitch. In addition, any .NET language can use these classes so every developer who chooses to use Visual Studio .NET to create applications can perform debugging operations using its visual tools.

The various tracing and debugging techniques are especially useful for applications that use threads. If implemented well, these techniques allow developers to trace each thread's behavior, discovering any application anomalies, such as unexpected resource consumption, contention bugs, and so on.

In this chapter, we will analyze both tracing and debugging aspects in the following order:

• Using Visual Studio .NET debugging analysis and its powerful tools

• Using the .NET tracing classes in order to implement these features in our code

• Putting it all together by creating an application that uses tracing

For this chapter, Visual Studio .NET is necessary to make use of much of the tracing and debugging features shown. However, by using the /d:TRACE=TRUE switch, some tracing functionality can be achieved using the command line.

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