Concurrent Program or Parallel Programming in C# in windows application

Well, you're going to have to design your code to be as efficient as possible. There are any unmber of ways this can be done. Which one is appropriate is going to take a bunch of research and testing on YOUR PART. to figure this out.

We have no idea what you know about threading in C# nor anything about your requirements so it's impossible to tell you which way to go. At best,m you'll get suggestions, but nothing is going to save you from a bunch of research and testing work.

Keep in mind, that no matter what method you chose, throwing piles and piles of threads at a computational problem does NOT get you more and more performance. A CPU can only run so many threads at one time, and it's usually limited to 8 or less right now on a Hyperthreaded Quad-Core CPU.

You can't execute 1000 functions in true parallel: not unless your PC has 1000+ cores, as you need a core to process each thread. However, you can get up to the number of cores you have running truly in parallel as separate threads, either by using Threading manually, or via Parallel.For[^]

However, be aware that creating and starting threads takes time, so 1000 small jobs set up as individual threads may well take more real time to execute than the same 1000 small jobs done consecutively!