AsyncEnumerator 2.1.0

Introduces IAsyncEnumerable, IAsyncEnumerator, ForEachAsync(), and ParallelForEachAsync()


Helps to (a) create an element provider, where producing an element can take a lot of time
due to dependency on other asynchronous events (e.g. wait handles, network streams), and
(b) a consumer that processes those element as soon as they are ready without blocking
the thread (the processing is scheduled on a worker thread instead).


using System.Collections.Async;

static IAsyncEnumerable<int> ProduceAsyncNumbers(int start, int end)
 return new AsyncEnumerable<int>(async yield => {

   // Just to show that ReturnAsync can be used multiple times
   await yield.ReturnAsync(start);

   for (int number = start + 1; number <= end; number++)
     await yield.ReturnAsync(number);

   // You can break the enumeration loop with the following call:

   // This won't be executed due to the loop break above
   await yield.ReturnAsync(12345);

// Just to compare with synchronous version of enumerator
static IEnumerable<int> ProduceNumbers(int start, int end)
 yield return start;

 for (int number = start + 1; number <= end; number++)
   yield return number;

 yield break;

 yield return 12345;

static async Task ConsumeNumbersAsync()
 var asyncEnumerableCollection = ProduceAsyncNumbers(start: 1, end: 10);
 await asyncEnumerableCollection.ForEachAsync(async number => {
   await Console.Out.WriteLineAsync($"{number}");

// Just to compare with synchronous version of enumeration
static void ConsumeNumbers()
 var enumerableCollection = ProduceNumbers(start: 1, end: 10);
 foreach (var number in enumerableCollection) {

There is a newer version of this package available.
See the version list below for details.
Install-Package AsyncEnumerator -Version 2.1.0
dotnet add package AsyncEnumerator --version 2.1.0
<PackageReference Include="AsyncEnumerator" Version="2.1.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add AsyncEnumerator --version 2.1.0
The NuGet Team does not provide support for this client. Please contact its maintainers for support.

Release Notes

2.1.0: New extension methods: Batch, UnionAll, Single, SingleOrDefault, DefaultIfEmpty, Cast.
2.0.0: Revise design of the library: same features, but slight paradigm shift and interface breaking changes.
1.5.0: Add support for .NET Standard, minor improvements.
1.4.2: Add finalizer to AsyncEnumerator and call Dispose in ForEachAsync and ParallelForEachAsync extension methods.
1.4.0: Add new generic type AsyncEnumeratorWithState for performance optimization.
      Now IAsyncEnumerator<T> is covariant.
      Add ForEachAsync, ParallelForeachAsync, and LINQ-style extension methods for IAsyncEnumerator.
1.2.1: New Linq-style extension methods in System.Collections.Async namespace.
1.1.0: Add ParallelForEachAsync extension methods for IEnumerable<T> and IAsyncEnumerable<T> in System.Collections.Async namespace.


This package has no dependencies.

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Version History

Version Downloads Last updated
3.0.2-beta 10,212 4/9/2019
3.0.0-beta1 8,779 2/23/2019
2.2.2 216,851 1/27/2019
2.2.1 379,814 5/29/2018
2.2.0 13,006 5/18/2018
2.1.1 78,527 1/20/2018
2.1.0 151,437 5/22/2017
2.0.1 42,597 2/13/2017
1.5.0 2,968 2/12/2017
1.4.2 1,005 2/6/2017
1.3.0 1,276 1/20/2017
1.2.3 6,317 1/6/2017
1.2.2 1,257 12/11/2016
1.2.1 358 12/10/2016
1.2.0 12,980 11/29/2016
1.1.3 378 11/28/2016
1.1.2 16,122 8/29/2016
1.0.3 1,814 4/28/2016
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