Debounce and Throttle Event Handlers

Debounce_Throttle.cs

// https://www.meziantou.net/debouncing-throttling-javascript-events-in-a-blazor-application.htm

Action<T> Debounce<T>(Action<T> action, TimeSpan interval)
{
    if (action == null) throw new ArgumentNullException(nameof(action));

    var last = 0;
    return arg =>
    {
        // increment while calls of the event are coming
        var current = System.Threading.Interlocked.Increment(ref last);

        // first incoming event starts the delayed invocation of the action
        Task.Delay(interval).ContinueWith(task =>
        {
            // excute action after a period of time where no changes happen
            if (current == last)
            {
                action(arg);
            }
        });
    };
}

Action<T> Throttle<T>(Action<T> action, TimeSpan interval)
{
    if (action == null) throw new ArgumentNullException(nameof(action));

    // captured in closure: 
    // .. the delivering delayed task
    Task task = null;
    // .. a lock handle 
    var l = new object();
    // .. a storage for the calling args
    T args = default;
    return (T arg) =>
    {
        // the latest calling args are kept for later use
        args = arg;
        
        // if the delayed delivery is already initialized, return
        if (task != null)
            return;

        // starts the delayed deleivery task, once!
        lock (l)
        {
            // double locking...
            if (task != null)
                return;

            // after exipry of the interval the latest args are delivered to the receiver
            task = Task.Delay(interval).ContinueWith(t =>
            {
                action(args);
                task = null;
            });
        }
    };
}