Performance Optimization & Profiling

Measure before optimizing — Visual Studio's built-in profiler (or dotnet-trace) shows where a running .NET program actually spends its time and memory.

Common, high-value fixes once a real bottleneck is found:

• Choosing the right collection — a Dictionary lookup is O(1), a linear List search is O(n), exactly as in Java.
• Avoiding unnecessary allocations in a hot loop (e.g. string concatenation with + instead of StringBuilder, revisited from Level 1 now at scale).
• Batching database calls through EF Core instead of triggering a query per item in a loop (the same N+1 query problem covered for Java).

Common mistakes

• "Optimizing" code with no profiler data to justify it — as in every language covered so far, this usually costs readability for no measurable benefit.