Debugging

After a few weeks of coding, you'll enter the inevitable task of debugging and resolving defects in your code. For this stage in the software lifecycle to be successful, you need to know how to debug and test your code, and how to resolve errors. For more information about unit testing in general, see our section on Unit Test Plans. For optimizing your application and testing it's performance under load, see the section on Optimization.

Configuring the Debugging Environment

Configuring your debugging environment is straightforward using Visual Studio.NET. Unlike classic ASP, which required opening up multiple IDEs such as Visual Interdev and Visual Basic to debug your application, you can debug your application from within a single Visual Studio.NET instance. Open your web project. Notice in the Solution Explorer that one project name is bold. This is the StartUp Project: the project that is first loaded when you enter debug mode. Make sure your web application, and not a class library, is set as your StartUp Project. Next, select an aspx page, right click, and select Set As Start Page. This will be the page loaded when you enter debug mode. You also want to verify that you are using the Debug build configuration. On the toolbar, notice the dropdown that has options for Debug, Release, and Configuration Manager. Be sure this is set to Debug, or your breakpoints will not work.

Applying Debugging Code

Next, open a code-behind file, right click a line of code and select Insert Breakpoint. Now select Debug->Start, or press F5. Visual Studio.NET will load your web application and stop at your breakpoint. You can then select Debug->Step Into (F11) or Debug->Step Over (F10) to go through your source code line-by-line. Using the Locals window, you can see the values of all local variables. The Watch window allows you to indicate a specific variable to watch.