Stop Parallelizing Everything: A Practical Guide to Parallel.ForEach
Parallel.ForEach feels like a free speed boost, until it slows your app to a crawl. This post explains when parallel loops shine, when they backfire, and how to avoid the classic traps. You will see small runnable C# examples for CPU bound work, shared state pitfalls, and I/O scenarios. We will also cover safer async alternatives, thread local aggregation, and simple tuning with ParallelOptions. By the end, you will know how to pick the right approach and measure the impact with confidence.
