Develop Reference

Aspnet core Parallels operation DbContext problem

I've a problem when I use Pararrel function in aspnetcore, in particular when in the cycle i try to save something in database. I get my data from externarl api and deseserialize it in my class.
This is the Parallel code.
Root players = JsonConvert.DeserializeObject<Root>(responseStream);
var bulkhead = Policy.BulkheadAsync(10, Int32.MaxValue);
var tasks = new List<Task>();
foreach (var player in players.players)
{
var t = bulkhead.ExecuteAsync(async () =>
{
int wyId = Convert.ToInt32(player.wyId);
HttpRequestMessage secondRequest = createRequest("https://apirest.com/v2/players/" + wyId + "?details=currentTeam&imageDataURL=true");
var client2 = _clientFactory.CreateClient();
var response2 = await client2.SendAsync(secondRequest);
if (response2.IsSuccessStatusCode)
{
var responseStream2 = await response2.Content.ReadAsStringAsync();
dynamic playerFullDetails = JsonConvert.DeserializeObject<dynamic>(responseStream2);
int wyId2 = Convert.ToInt32(playerFullDetails.wyId);
int marketValue = 0;
HttpRequestMessage tirthRequest = createRequest("https://apirest.com/v2/players/" + wyId2 + "/marketvalue");
var client3 = _clientFactory.CreateClient();
var response3 = await client3.SendAsync(tirthRequest);
if (response3.IsSuccessStatusCode)
{
var responseStream3 = await response3.Content.ReadAsStringAsync();
dynamic marketValueResponse = JsonConvert.DeserializeObject<dynamic>(responseStream3);
if (marketValueResponse.marketValue != 0)
{
marketValue = Convert.ToInt32(marketValueResponse.marketValue);
}
}
DateTime birthday = Convert.ToDateTime(playerFullDetails.birthDate);
int age = DateTime.Now.Year - birthday.Year;
Player finalPlayer = new Player();
finalPlayer.PlayerId = wyId2;
finalPlayer.MarketValue = marketValue;
finalPlayer.Value = Convert.ToDouble(marketValue) / Convert.ToDouble(1000000);
finalPlayer.Firstname = playerFullDetails.firstName;
finalPlayer.Lastname = playerFullDetails.lastName;
finalPlayer.Name = playerFullDetails.shortName;
finalPlayer.Position = playerFullDetails.role.name;
finalPlayer.Height = playerFullDetails.height;
finalPlayer.Foot = playerFullDetails.foot;
finalPlayer.IsLocked = false;
finalPlayer.Team = playerFullDetails.currentTeam != null ? playerFullDetails.currentTeam.name : "";
finalPlayer.TeamId = playerFullDetails.currentTeam != null ? playerFullDetails.currentTeam.wyId : 0;
finalPlayer.CompetitionId = 524;
finalPlayer.UpdatedDay = DateTime.Now;
finalPlayer.League = "Serie A";
finalPlayer.Age = age;
Player playerExist = await _context.Player.Where(x => x.PlayerId == wyId2).SingleOrDefaultAsync();
if (playerExist == null)
{
if (finalPlayer.TeamId != 0)
{
await _context.Player.AddAsync(finalPlayer);
await _context.SaveChangesAsync();
}
}
if (finalPlayer.TeamId != 0)
{
Team teamExist = await _context.Team.Where(x => x.TeamId == finalPlayer.TeamId).SingleOrDefaultAsync();
if (teamExist == null)
{
Team team = new Team();
team.TeamId = finalPlayer.TeamId;
team.TeamName = finalPlayer.Team;
await _context.Team.AddAsync(team);
await _context.SaveChangesAsync();
}
}
}
});
tasks.Add(t);
}
await Task.WhenAll(tasks);
The function isert 50/60 (in total would be 500) element in db and finally i receive this error
A second operation was started on this context before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext. For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913.
Thanks

It's best practice to use 1 dbcontext per unit of work, and the dbcontext is not thread safe
So either create a new dbcontext per thread or lock access with someting like a semaphore otherwise you will always get unstable code

UWP MediaFrameReader - System.ArgumentException: 'Value does not fall within the expected range.'

I am trying to create a UWP application that uses the laptop's webcam to process mediaframes on which I want to search faces using Microsoft Azure Face API.
I created a MediaCapture that works well, and a MediaFrameReader, which throws the exception mentioned in the question's title.
You can see my code here:
private async void StartDetection()
{
mediaStream = new InMemoryRandomAccessStream();
MediaEncodingProfile encodingProfile = MediaEncodingProfile.CreateMp4(encodingQuality);
await mediaCapture.StartRecordToStreamAsync(encodingProfile, mediaStream);
var frameSourceGroups = await MediaFrameSourceGroup.FindAllAsync();
MediaFrameSourceGroup selectedGroup = null;
MediaFrameSourceInfo colorSourceInfo = null;
foreach (var sourceGroup in frameSourceGroups)
{
foreach (var sourceInfo in sourceGroup.SourceInfos)
{
if (sourceInfo.MediaStreamType == MediaStreamType.VideoRecord
&& sourceInfo.SourceKind == MediaFrameSourceKind.Color)
{
colorSourceInfo = sourceInfo;
break;
}
}
if (colorSourceInfo != null)
{
selectedGroup = sourceGroup;
break;
}
}
var selectedGroupObjects = frameSourceGroups.Select(group =>
new
{
sourceGroup = group,
colorSourceInfo = group.SourceInfos.FirstOrDefault((sourceInfo) =>
{
// On Xbox/Kinect, omit the MediaStreamType and EnclosureLocation tests
return sourceInfo.MediaStreamType == MediaStreamType.VideoRecord
&& sourceInfo.SourceKind == MediaFrameSourceKind.Color
&& sourceInfo.DeviceInformation?.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Front;
})
}).Where(t => t.colorSourceInfo != null).FirstOrDefault();
selectedGroup = selectedGroupObjects?.sourceGroup;
colorSourceInfo = selectedGroupObjects?.colorSourceInfo;
if (selectedGroup == null)
{
return;
}
var allGroups = await MediaFrameSourceGroup.FindAllAsync();
var eligibleGroups = allGroups.Select(g => new
{
Group = g,
SourceInfos = new MediaFrameSourceInfo[]
{
g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Color),
g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Depth),
g.SourceInfos.FirstOrDefault(info => info.SourceKind == MediaFrameSourceKind.Infrared),
}
}).Where(g => g.SourceInfos.Any(info => info != null)).ToList();
if (eligibleGroups.Count == 0)
{
System.Diagnostics.Debug.WriteLine("No source group with color, depth or infrared found.");
return;
}
var selectedGroupIndex = 0;
selectedGroup = eligibleGroups[selectedGroupIndex].Group;
colorSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[0];
MediaFrameSourceInfo infraredSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[1];
MediaFrameSourceInfo depthSourceInfo = eligibleGroups[selectedGroupIndex].SourceInfos[2];
var colorFrameSource = mediaCapture.FrameSources[colorSourceInfo.Id];
var preferredFormat = colorFrameSource.SupportedFormats.Where(format =>
{
return format.VideoFormat.Width >= 1080
&& format.Subtype == "RGB24";
}).FirstOrDefault();
if (preferredFormat == null)
{
return;
}
await colorFrameSource.SetFormatAsync(preferredFormat);
MediaFrameReader mediaFrameReader;
mediaFrameReader = await mediaCapture.CreateFrameReaderAsync(colorFrameSource, preferredFormat.Subtype);
mediaFrameReader.FrameArrived += CheckFrameForFaces;
await mediaFrameReader.StartAsync();
}
private async void CheckFrameForFaces(MediaFrameReader sender, MediaFrameArrivedEventArgs args)
{
var mediaFrame = sender.TryAcquireLatestFrame(); // -> this is the line that throws the exception
var videoFrame = mediaFrame?.VideoMediaFrame;
var bitmap = videoFrame?.SoftwareBitmap;
WriteableBitmap wb = new WriteableBitmap(bitmap.PixelWidth, bitmap.PixelHeight);
bitmap.CopyToBuffer(wb.PixelBuffer);
var img = Dlib.LoadImageData<RgbPixel>(wb.PixelBuffer.ToArray(), (uint)wb.PixelHeight, (uint)wb.PixelWidth, 3);
ImageWindow im = new ImageWindow(img);
im.WaitUntilClosed();
}
This code by the way is written based on the Microsoft documentation, which can be found here:
https://learn.microsoft.com/en-us/windows/uwp/audio-video-camera/process-media-frames-with-mediaframereader
The only thing I changed is the MediaEncodingSubtype, because it didn't worked with Argb32, so I use Rgb24 (I checked all the supported formats in my computer). And I think the problem is derived from this property. When I initialize the MediaFrameReader object with the subtype Argb32 (as you can see in the documentation example) I get no exception, although the SoftwareBitmap will be null. On the other hand, if I use Rgb24 (because the preferredFormat has this subtype) I get the exception.
I can show some details of the exception:
System.ArgumentException
HResult=0x80070057
Message=Value does not fall within the expected range.
Source=Windows
StackTrace:
at Windows.Media.Capture.Frames.MediaFrameReader.TryAcquireLatestFrame()
at FaceAPI.MainPage.<CheckFrameForFaces>d__17.MoveNext() in P:\Dokumentumok\Suli\BME-VIK_6\Klitech\Házi feladat\KlitechHF\FaceAPI\FaceAPI\MainPage.xaml.cs:line 217

Paging with CosmosClient in CosmosDB

I'm trying to implement paging using the SDK v3 CosmosClient instead of the old DocumentClient.
Reason for this is it seems DocumentClient doesn't translate LINQ queries that contains spatial functions very well (ie: When using Within() I'll get an error from DocumentClient stating the methods is not implemented).
Paging works well with DocumentClient.CreateDocumentQuery<T> as such:
var query = DocumentClient.CreateDocumentQuery<T>(UriFactory.CreateDocumentCollectionUri("master", "features"), feedOptions)
.Where(t => t.Type == typeof(T).Name)
.Where(pred)
.AsDocumentQuery();
string queryContinuationToken = null;
var page = await query.ExecuteNextAsync<T>();
if (query.HasMoreResults)
queryContinuationToken = page.ResponseContinuation;
I'm at a little loss as to where to gather a continuation token using CosmosClient and its Container class:
QueryRequestOptions options = new QueryRequestOptions();
options.MaxItemCount = maxRecords;
FeedIterator<T> feed;
if (continuationToken == "")
feed = Container.GetItemLinqQueryable<T>(true, null, options).Where(x => x.Type == typeof(T).Name).Where(pred).ToFeedIterator();
else
feed = Container.GetItemLinqQueryable<T>(true, continuationToken, options).Where(x => x.Type == typeof(T).Name).Where(pred).ToFeedIterator();
FeedIterator seems to have some of the members IDocumentQuery has (like HasMoreResults) but I can't find a continuation token anywhere.
What am I missing?

Alright, here's a Where method I implemented. Seems to work at first glance.
If you do var f = feed.ReadNextAsync() you won't get an object that's of type FeedResponse, preventing you access to the token. You need to declare f explicitly of type FeedResponse<T>
public async Task<(IEnumerable<T> Results, string ContinuationToken)> Where<T>(Expression<Func<T, bool>> pred, int maxRecords = 0, string partitionKey = "", string continuationToken = "") where T : IDocumentModel
{
QueryRequestOptions options = new QueryRequestOptions();
if (partitionKey != "")
options.PartitionKey = new PartitionKey(partitionKey);
if (maxRecords == 0)
{
return (Container.GetItemLinqQueryable<T>(true, null, options).Where(x => x.Type == typeof(T).Name).Where(pred), "");
}
else
{
options.MaxItemCount = maxRecords;
string token = "";
FeedIterator<T> feed;
List<T> res = new List<T>();
if (continuationToken == "")
feed = Container.GetItemLinqQueryable<T>(true, null, options).Where(x => x.Type == typeof(T).Name).Where(pred).ToFeedIterator();
else
feed = Container.GetItemLinqQueryable<T>(true, continuationToken, options).Where(x => x.Type == typeof(T).Name).Where(pred).ToFeedIterator();
Microsoft.Azure.Cosmos.FeedResponse<T> f = await feed.ReadNextAsync();
token = f.ContinuationToken;
foreach (var item in f)
{
res.Add(item);
}
return (res, token);
}
}

With the version 3.12.0 of the Cosmos SDK the following works as expected as a pretty much in place replacement for the older DocumentQuery.
Original DocumentClient method for comparison:
IDocumentQuery<ToDoItem> query = client.CreateDocumentQuery<ToDoItem>(collectionUri)
.Where(t => t.Description.Contains(searchterm))
.AsDocumentQuery();
while (query.HasMoreResults)
{
foreach (ToDoItem result in await query.ExecuteNextAsync())
{
log.LogInformation(result.Description);
}
}
Using a CosmosClient this becomes:
var database = client.GetDatabase("ToDoItems");
var container = database.GetContainer("Items");
var query = container.GetItemLinqQueryable<ToDoItem>()
.Where(t => t.Description.Contains(searchTerm))
.ToFeedIterator();
while (query.HasMoreResults)
{
foreach (ToDoItem result in await query.ReadNextAsync())
{
log.LogInformation(result.Description);
}
}
So your query is now a FeedIterator, and you can call HasMoreResults and ReadNextAsync on it.
Admittedly this won't get you access to the diagnostics, request charge, etc. that comes on the FeedIterator, but it will page through the results cleanly.

IQueryable<returnVModel> query;
var requestOptions = new QueryRequestOptions
{
MaxItemCount = 20
};
if (Token == "" || Token == null)
{
query = Container.GetItemLinqQueryable<returnVModel>(false, null, requestOptions).Where(x => x.id == id);
}
else
{
query = Container.GetItemLinqQueryable<returnVModel>(false, Token, requestOptions).Where(x => x.id == id);
}
var ct = new CancellationTokenSource();
var totalCount = await query.CountAsync(ct.Token); //Total Count
var feedIterator = query.ToFeedIterator();
var queryResults = new List<returnVModel>();
FeedResponse<returnVModel> feedResults = await feedIterator.ReadNextAsync(ct.Token);
queryResults.AddRange(feedResults); // Output
var PaginationToken = feedResults.ContinuationToken //Token
First time we need to pass token as null, from next page onwards pass the token which we received in previous output.
Pagination was working fine in v3.

How to speed up workflow with database .Net

I have simple controller that return list of products.It is take about 5-7sec to return the data for the first time,and then 50-80ms ,but only if i run it immediately(10-30sec) after first one ,if i will run it after 2-3min it will be again 5-7s.
I dont store this list in cache,sow i cant understand why only first time it takes 5sec,and then 50ms.
Important:test that i have made is not on localhost,it is on the production server.On localhost it takes 50ms
How can i speed up?
Do i need to make any change in my code? Or IIS?
My code
public List<PackageModel> GetPromotionOrDefaultPackageList(string domain)
{
List<DBProduct> DBPackageList = new List<DBProduct>();
List<PackageModel> BllPackageList = new List<PackageModel>();
try
{
using (CglDomainEntities _entities = new CglDomainEntities())
{
DBPackageList = _entities.DBProducts
.Where(x =>
x.ProductGroup.Equals(domain + "-package")
&& x.IsPromotionProduct == true)
.ToList();
if (DBPackageList.Count == 0)
{
DBPackageList = _entities.DBProducts
.Where(x =>
x.ProductGroup.Equals(domain + "-package")
&& x.IsBasicProduct == true)
.ToList();
}
}
PackageModel bllPackage = new PackageModel();
foreach (DBProduct dbProduct in DBPackageList)
{
bllPackage = new PackageModel();
bllPackage.Id = dbProduct.Id;
bllPackage.ProductId = dbProduct.ProductId;
bllPackage.IsPromotionProduct = dbProduct.IsPromotionProduct.HasValue ? dbProduct.IsPromotionProduct.Value : false;
bllPackage.ProductName = dbProduct.ProductName;
bllPackage.ProductDescription = dbProduct.ProductDescription;
bllPackage.Price = dbProduct.Price;
bllPackage.Currency = dbProduct.Currency;
bllPackage.CampaignId = dbProduct.CampaignId;
bllPackage.PathToProductImage = dbProduct.PathToProductImage;
bllPackage.PathToProductPromotionImage = dbProduct.PathToProductPromotionImage;
bllPackage.PathToProductInfo = dbProduct.PathToProductInfo;
bllPackage.CssClass = dbProduct.CssClass;
BllPackageList.Add(bllPackage);
}
return BllPackageList;
}
catch (Exception ex)
{
Logger.Error(ex.Message);
return BllPackageList;
}
}

C# ef second operation started before previous asynchronous operation completed

Just trying to do normal query on ef but getting below error message
"A second operation started on this context before a previous asynchronous operation completed"
I am using await for all aync call but not sure what could be causing this issue.
here' code
var sids = await context.Sites.Where(s => slist.Contains(s.JVSiteID)).ToListAsync();
var header = await context.GenericCsvHeaders.FirstOrDefaultAsync(x => x.Header == csvh) ?? new GenericCsvHeader { Header = csvh };
context.Entry<GenericCsvHeader>(header).State = (header.GenericCsvHeaderID == 0) ? EntityState.Added : EntityState.Unchanged;
var sa = await context.SAs.Where(x => x.StatusID == Data.Enum.Status.Active && mapkeys.Contains(x.SAName)).Select(x => new { x.SAName, x.SACode, x.SAID }).ToListAsync();
if (sa.Count > 0)
sasitelist = await context.Site_SA.Where(x => x.StatusID == Data.Enum.Status.Active && siteids.Contains(x.SiteID ?? 0)).ToListAsync();
var az = await context.Azimuths.Where(x => x.StatusID == Data.Enum.Status.Active && mapkeys.Contains(x.AzimuthName)).Select(x => new { x.AzimuthName, x.AzimuthID }).ToListAsync();
if (az.Count > 0)
azsitelist = await context.Site_Azimuth.Where(x => x.StatusID == Data.Enum.Status.Active && siteids.Contains(x.SiteID ?? 0)).ToListAsync();
var rows = new List<dynamic>(); //getting this list from csv file via csvHelper
foreach (var r in rows)
{
var s = sids.FirstOrDefault(x => x.JVSiteID == (((IDictionary<String, Object>)r)[siteid]).ToString()) ?? new Site();
UpdateSite(s, r, map);
}
private async void UpdateSite(Site site, dynamic csvSite, IDictionary<string, string> map)
{
context.Entry(site).State = (site.StateID == 0) ? EntityState.Added : EntityState.Modified;
site.SiteForAuditTrail = site;
if (map.ContainsKey("SiteName") && !String.IsNullOrWhiteSpace(GetStringOfDynamic(map,csvSite,"SiteName")))
site.SiteName = GetStringOfDynamic(map,csvSite, "SiteName");
if (map.ContainsKey("State") && !String.IsNullOrWhiteSpace(GetStringOfDynamic(map,csvSite, "State")))
{
//getting exception at below line
var state = (await GetRefTypeList<State>(x => x.StateCode == GetStringOfDynamic(map,csvSite, "State"))) ?? new State { StateCode = GetStringOfDynamic(map,csvSite, "State") };
context.Entry(state).State = (state.StateID == 0) ? EntityState.Added : EntityState.Unchanged;
site.State = state;
state.SiteForAuditTrail = site;
}
}
private async Task<T> GetRefTypeList<T>(Func<T, bool> expression) where T : EntityBase
{
if (!refTypes.ContainsKey(typeof(T).Name))
refTypes[typeof(T).Name] = (await context.Set<T>().Where(x => x.StatusID == Data.Enum.Status.Active).ToListAsync());
return (refTypes[typeof(T).Name] as List<T>)?.FirstOrDefault(expression);
}
private string GetStringOfDynamic(IDictionary<string, string> map,dynamic obj, string propertyName)
{
if (((IDictionary<String, Object>)obj).ContainsKey(map[propertyName]))
return (((IDictionary<String, Object>)obj)[map[propertyName]]??"").ToString();
return "";
}

found problem, was missing await when calling UpdateSite
foreach (var r in rows)
{
var s = sids.FirstOrDefault(x => x.JVSiteID == (((IDictionary<String, Object>)r)[siteid]).ToString()) ?? new Site();
**await** UpdateSite(s, r, map);
}

You are having a race condition here. While you are using await you have other code executing potentially before the variable sids, header, sa and az, have been returned.
You should refactor your code so that the remaining code is not executed until these variables are returned. You can do this by using a task and then using the extension WhenAll which will ensure each await has been completed before proceeding. Here is a link to MS docs on Task and WhenAll implementation