Convert IAsyncEnumerable to List
C#LinqIenumerableC# 8.0IasyncenumerableC# Problem Overview
So in C#8 we got the addition of the IAsyncEnumerable
interface.
If we have a normal IEnumerable
we can make a List
or pretty much any other collection we want out of it. Thanks to Linq there.
var range = Enumerable.Range(0, 100);
var list = range.ToList();
Well now I want to convert my IAsyncEnumerable
to a List
and this of course asynchronously. Are there already Linq implementations for that case? If there isn't, how could I convert it myself then?
C# Solutions
Solution 1 - C#
Sure - you just need the ToListAsync()
method, which is in the System.Linq.Async
NuGet package. Here's a complete example:
Project file:
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>netcoreapp3.1</TargetFramework>
</PropertyGroup>
<ItemGroup>
<PackageReference Include="System.Linq.Async" Version="4.0.0" />
</ItemGroup>
</Project>
Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
class Program
{
static async Task Main(string[] args)
{
IAsyncEnumerable<string> sequence = GetStringsAsync();
List<string> list = await sequence.ToListAsync();
Console.WriteLine(list.Count);
}
static async IAsyncEnumerable<string> GetStringsAsync()
{
yield return "first";
await Task.Delay(1000);
yield return "second";
await Task.Delay(1000);
yield return "third";
}
}
Solution 2 - C#
On the off chance that you don't want to to bring in a NuGet package, here is (probably something similar to) the extension method mentioned in the package:
public static class AsyncEnumerableExtensions
{
public static async Task<List<T>> ToListAsync<T>(this IAsyncEnumerable<T> items,
CancellationToken cancellationToken = default)
{
var results = new List<T>();
await foreach (var item in items.WithCancellation(cancellationToken)
.ConfigureAwait(false))
results.Add(item);
return results;
}
}