Poller.cs

public class Poller<TData>
{
    private readonly Func<Task<TData>> _func;
    private Task<TData> _task;
    private int _hasData;

    // Returns default values before first poll. 
    public TData Data { get; private set; }
    public bool HasData => _hasData == 1;

    public Poller(Func<Task<TData>> func)
    {
        _func = async () =>
        {
            var result = await func();
            Data = result;
            return result;
        };
    }

    public Task<TData> PollAsync(bool refresh = false)
    {
        // First call polls data.
        if (_hasData == 0 &&
            Interlocked.CompareExchange(ref _hasData, 1, 0) == 0)
        {
            _task = _func();
        }
        // Force polls and replaces data when done.
        else if (refresh)
        {
            return _func().ContinueWith(_ =>
                {
                    _task = _;
                    return _.GetAwaiter().GetResult();
                },
                CancellationToken.None,
                TaskContinuationOptions.ExecuteSynchronously,
                TaskScheduler.Default);
        }

        return _task;
    }
}