Cancel Obsolete Http Requests in Rx.NET with the Switch Operator, see https://blog.dangl.me/archive/cancel-obsolete-http-requests-in-rxnet-with-the-switch-operator/

first_approach.cs

_requestUrl
    .Subscribe(async url =>
    {
        var response = await httpClient.GetAsync(url);
        // Update the list
    });

with_cancellation.cs

_requestUrl
    .Select(url => httpClient.GetAsync(url))
    .Switch()
    .Subscribe(response =>
    {
        // Update the list
    });