Cancelling ListFolderLongpollAsync

Hi,

I have a Dropbox longpoll running as a task, implemented in C# (Xamarin Forms) as the following.

async Task DropboxLongpoll (string cursor, CancellationToken token)
		{
			var longpollClient = this.GetClient ();
			int backoff = 0;
			System.Diagnostics.Debug.WriteLine ("Running background longpoll task.");
			while (!token.IsCancellationRequested) {
				var longpollResults = await longpollClient.Files.ListFolderLongpollAsync (cursor); //default timeout is 30 seconds
				System.Diagnostics.Debug.WriteLine ("Changes: " + longpollResults.Changes + " Backoff: " + longpollResults.Backoff.GetValueOrDefault ());
				if (longpollResults.Changes) {
					var folderResult = await longpollClient.Files.ListFolderContinueAsync (cursor);
					cursor = folderResult.Cursor;
					DropboxLongpollReportChanges (folderResult);
				}
				//backoff if present
				if (longpollResults.Backoff != null) {
					backoff = (int)longpollResults.Backoff.GetValueOrDefault ();
				}
				System.Diagnostics.Debug.WriteLine ("Backing off longpoll for " + backoff + " seconds");
				await Task.Delay (backoff * 1000); //milliseconds delay
			}
			System.Diagnostics.Debug.WriteLine ("Cancelling task");
			longpollClient.Dispose ();
			token.ThrowIfCancellationRequested ();
			System.Diagnostics.Debug.WriteLine ("Task finished");
		}

While I can nicely cancel (i.e., the while loop stops) this task by calling Cancel on the CancellationTokenSource from which I got the token, the Dropbox longpoll task seems to keep running, i.e., listening for changes. I can ignore the changes it reports by modifying this code to the following.

async Task DropboxLongpoll (string cursor, CancellationToken token)
		{
			var longpollClient = this.GetClient ();
			int backoff = 0;
			System.Diagnostics.Debug.WriteLine ("Running background longpoll task.");
			while (!token.IsCancellationRequested) {
				var longpollResults = await longpollClient.Files.ListFolderLongpollAsync (cursor); //default timeout is 30 seconds
                if (!token.IsCancellationRequested) { //check if the cancellation is still not requested
				System.Diagnostics.Debug.WriteLine ("Changes: " + longpollResults.Changes + " Backoff: " + longpollResults.Backoff.GetValueOrDefault ());
				if (longpollResults.Changes) {
					var folderResult = await longpollClient.Files.ListFolderContinueAsync (cursor);
					cursor = folderResult.Cursor;
					DropboxLongpollReportChanges (folderResult);
				}
				//backoff if present
				if (longpollResults.Backoff != null) {
					backoff = (int)longpollResults.Backoff.GetValueOrDefault ();
				}
				System.Diagnostics.Debug.WriteLine ("Backing off longpoll for " + backoff + " seconds");
				await Task.Delay (backoff * 1000); //milliseconds delay
				} else {
					System.Diagnostics.Debug.WriteLine ("Cancelling task");
					longpollClient.Dispose ();
					token.ThrowIfCancellationRequested ();
				}
			}
			System.Diagnostics.Debug.WriteLine ("Task finished");
		}

But, this is just ignoring the detected changes. I believe that the long poll will keep running as a background thread. Will the Dropbox longpoll async task actually cancel? Is there a way to pass the token to the ListFolderLongpollAsync so that it actually cancel when cancellation is requested?