How can I isolate the problematic part of my application code that's causing an "HTTP Error 500" when debugging on localhost with IIS?

To isolate code issues, you can: 1. **Enable detailed errors:** (as per Q1) to see the full exception stack trace directly in the browser. 2. **Attach a debugger:** In Visual Studio, go to "Debug" -> "Attach to Process...", select the `w3wp.exe` process corresponding to your application pool, and set breakpoints in your code. 3. **Implement robust logging:** Use a logging framework (e.g., NLog, Serilog, log4net) within your application to log detailed information and exceptions to a file or database, which can be reviewed after the error occurs. 4. **Systematic commenting/simplification:** Temporarily comment out or simplify parts of your code to narrow down which section is causing the unhandled exception.