One of the nicest new features in C# 8 is IAsyncEnumerable/IAsyncEnumerator. Normally it requires types from the upcoming .NET Standard 2.1 to compile and run, which will be present in .NET Core 3, but will not be added to .NET Framework 4.8. However, as with System.Threading.Tasks, the C# 8 compiler can use these types regardless of which assembly they are in, and the types themselves do not rely on new framework functionality for anything essential.

This package provides these types, forked from dotnet/coreclr with fixes to make them compile against .NET Standard 2.0.

To use IAsyncEnumerable and await foreach, add a reference to this package and a reference to the latest prerelease version of Microsoft.Net.Compilers to your project.

This package also adds IAsyncDisposable which enables await using.

In addition to the core types mentioned above, this package provides extension methods and helpers to make IAsyncEnumerator more like a first-class citizen. Refer to project wiki or XML documentation for details.