Most often you do know whether an API allocates. It is always possible to microbenchmark it with [MemoryDiagnoser] or profile it with VS or Rider. I absolutely

Most often you do know whether an API allocates. It is always possible to microbenchmark it with [MemoryDiagnoser] or profile it with VS or Rider. I absolutely love Rider's dynamic program analysis that just runs alongside me running an application with F5, ideally in release, and then I can go through every single allocation site and decide what to do. Even when allocations happen, .NET is much more tolerant to allocation traffic than, for example, Go. You can absolutely live with a few allocations here and there. If all you have are small transient allocations - it means that live object count will be very low, and all such allocations will die in Gen 0. In scenarios like these, it is uncommon to see infrequent sub-500us GC pauses. Last but not least, .NET is continuously being improved - pretty much all standard library methods already allocate only what's necessary (which can mean nothing at all), and with each release everything that has room for optimization gets optimized further. .NET 9 comes with object stack allocation / escape analysis enabled by default, and .NET 10 will improve this further. Even without this, LINQ for example is well-behaved and can be used far more liberally than in the past. It might sound surprising to many here but among all GC-based platforms, .NET gives you the most tools to manage the memory and control allocations. There is a learning curve to this, but you will find yourself fighting them much more rarely in performance-critical code than in alternatives.