/// <summary>
/// Perform the specified async action on each element
/// of the <see cref="List{T}"/> with the specified concurrency.
/// </summary>
public static Task ForEachAsync <T>(this IEnumerable <T> source, Func <T, Task> asyncAction, int concurrency,
CancellationToken cancellationToken = default)
{
source.ThrowIfArgumentNull(nameof(source));
asyncAction.ThrowIfArgumentNull(nameof(asyncAction));
concurrency.ThrowIfArgumentOutOfRange(1, int.MaxValue, nameof(concurrency));
async Task ForEachInner()
{
int throwedCount = 0;
void OnFault(Exception e)
{
Interlocked.Add(ref throwedCount, 1);
throw e;
}
using (var tasks = new TaskSet(concurrency, OnFault))
{
foreach (var x in source)
{
if (throwedCount > 0)
{
break;
}
cancellationToken.ThrowIfCancellationRequested();
await tasks.AddAsync(x, asyncAction).ConfigureAwait(false);
}
await tasks.WhenAll().ConfigureAwait(false);
}
}
return(ForEachInner());
}