Create empty IAsyncEnumerable

Question

I have an interface which is written like this:

public interface IItemRetriever
{
    public IAsyncEnumerable

        

Answer 1

If for any reason you don't want to install the package which is mentioned in Jon's answer, you can create the method AsyncEnumerable.Empty() like this:

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
public static class AsyncEnumerable
{
    public static IAsyncEnumerator Empty() => EmptyAsyncEnumerator.Instance;

    class EmptyAsyncEnumerator : IAsyncEnumerator
    {
        public static readonly EmptyAsyncEnumerator Instance = 
            new EmptyAsyncEnumerator();
        public T Current => default!;
        public ValueTask DisposeAsync() => default;
        public ValueTask MoveNextAsync() => new ValueTask(false);
    }
}

Note: The answer doesn't discourage using the System.Linq.Async package. This answer provides a brief implementation of AsyncEnumerable.Empty() for cases that you need it and you cannot/don't want to use the package. You can find the implementation used in the package here.