Parallel Loop State (feature request)

[sallgeud]

Current Parallel.ForEach passes a loop state to any method calls. This can be valuable as any break may necessitate immediate stoppage of the loop, which can be done by calling loopstate.Stop().

[kind-serge]

I would challenge you with such feature request and ask to think about using CancellationToken which is the recommended thing to use with asynchronous operations. Here is an example:

public IAsyncEnumerable Enumerate() =>
  new AsyncEnumerable(async yield =>
  {
    var result1 = await FooAsync(yield.CancellationToken);
    await yield.ReturnAsync(result1);

    var result2 = await BarAsync(yield.CancellationToken);
    await yield.ReturnAsync(result2);
  });
  
public async Task ProcessAsync(CancellationToken cancellationToken)
{
  var innerCts = new CancellationTokenSource();
  var combinedCancellationToken = CancellationTokenSource.CreateLinkedTokenSource(
    cancellationToken, innerCts.Token);
  
  await Enumerate().ForEachAsync(async item =>
  {
    if (...) // cancellation-control logic
      innerCts.Cancel(); // cancels all associated async tasks and ForEachAsync 
                         // will throw OperationCanceledException
  },
  cancellationToken: combinedCancellationToken);
}