private Task ProcessDriveChangesAsync(ref string deltaLink, Func <DriveItem, bool> relevancePredicate, Func <IEnumerable <DriveItem>, Task> action, string resetLink)
{
var graph = graphClientContext.GraphClient;
IDriveItemDeltaRequest deltaRequest = new DriveItemDeltaRequest(deltaLink, graph, null);
IDriveItemDeltaCollectionPage delta = null;
var preResult = new List <Task>();
do
{
try
{
delta = deltaRequest.GetAsync().Result;
}
catch (Exception e) when((e.InnerException as ServiceException)?.Error?.Code == "resyncRequired")
{
delta = new DriveItemDeltaRequest(resetLink, graph, null).GetAsync().Result;
}
var relevantItems = delta.Where(relevancePredicate);
if (!relevantItems.Any())
{
continue;
}
preResult.Add(action.Invoke(relevantItems));
} while ((deltaRequest = delta.NextPageRequest) != null);
deltaLink = (string)delta.AdditionalData["@odata.deltaLink"];
return(Task.WhenAll(preResult));
}
/// <summary>
/// Request the delta stream from OneDrive to find files that have changed between notifications for this account
/// </summary>
/// <param name="state">Our internal state information for the subscription we're processing.</param>
/// <param name="client">Graph client for the attached user.</param>
/// <param name="log">Tracewriter for debug output</param>
/// <returns></returns>
private static async Task <List <DriveItem> > FindChangedDriveItemsAsync(StoredSubscriptionState state, GraphServiceClient client, TraceWriter log)
{
string DefaultLatestDeltaUrl = idaMicrosoftGraphUrl + "/v1.0/drives/" + state.DriveId + "/root/delta?token=latest";
// We default to reading the "latest" state of the drive, so we don't have to process all the files in the drive
// when a new subscription comes in.
string deltaUrl = state?.LastDeltaToken ?? DefaultLatestDeltaUrl;
List <DriveItem> changedDriveItems = new List <DriveItem>();
// Create an SDK request using the URL, instead of building up the request using the SDK
IDriveItemDeltaRequest request = new DriveItemDeltaRequest(deltaUrl, client, null);
// We max out at 50 requests of delta responses, just for demo purposes.
const int MaxLoopCount = 50;
for (int loopCount = 0; loopCount < MaxLoopCount && request != null; loopCount++)
{
log.Info($"Making request for '{state.SubscriptionId}' to '{deltaUrl}' ");
// Get the next page of delta results
IDriveItemDeltaCollectionPage deltaResponse = await request.GetAsync();
// Filter to the audio files we're interested in working with and add them to our list
var changedFiles = (from f in deltaResponse
where f.File != null &&
f.Name != null &&
(f.Name.EndsWith(acceptedAudioFileExtension) || f.Audio != null) &&
f.Deleted == null
select f);
changedDriveItems.AddRange(changedFiles);
// Figure out how to proceed, whether we have more pages of changes to retrieve or not.
if (null != deltaResponse.NextPageRequest)
{
request = deltaResponse.NextPageRequest;
}
else if (null != deltaResponse.AdditionalData["@odata.deltaLink"])
{
string deltaLink = (string)deltaResponse.AdditionalData["@odata.deltaLink"];
log.Verbose($"All changes requested, nextDeltaUrl: {deltaLink}");
state.LastDeltaToken = deltaLink;
return(changedDriveItems);
}
else
{
// Shouldn't get here, but just in case, we don't want to get stuck in a loop forever.
request = null;
}
}
// If we exit the For loop without returning, that means we read MaxLoopCount pages without finding a deltaToken
log.Info($"Read through MaxLoopCount pages without finding an end. Too much data has changed and we're going to start over on the next notification.");
state.LastDeltaToken = DefaultLatestDeltaUrl;
return(changedDriveItems);
}