using System;

using System.Collections.Generic;

using System.Reactive.Linq;

using System.Linq;

​

var observable = Observable.Range(1, 100).Shuffle()

    .Subscribe(n => Console.Write($"{n}, "));

​

public static class ObservableHelper {

public static IObservable<T> RandomSample<T>(this IObservable<T> source, int sampleSize) 

    => source.Buffer(sampleSize, 1).Where(list => list.Count == sampleSize)

             .Select(list => list[Random.Shared.Next(0, sampleSize)]);

    public static IObservable<T> Shuffle<T>(this IObservable<T> source) {

        List<T> emittedValues = [];

        return source.Select(value => {

            emittedValues.Add(value);

            return emittedValues[Random.Shared.Next(0, emittedValues.Count)];

        });

    }

}