I used the following approach long time (approx 5 years):
Create one big class with initialization of XXXEntities in controller and create each method for each action with DB. Example:
public class DBRepository
{
private MyEntities _dbContext;
public DBRepository()
{
_dbContext = new MyEntities();
}
public NewsItem NewsItem(int ID)
{
var q = from i in _dbContext.News where i.ID == ID select new NewsItem() { ID = i.ID, FullText = i.FullText, Time = i.Time, Topic = i.Topic };
return q.FirstOrDefault();
}
public List<Screenshot> LastPublicScreenshots()
{
var q = from i in _dbContext.Screenshots where i.isPublic == true && i.ScreenshotStatus.Status == ScreenshotStatusKeys.LIVE orderby i.dateTimeServer descending select i;
return q.Take(5).ToList();
}
public void SetPublicScreenshot(string filename, bool val)
{
var screenshot = Get<Screenshot>(p => p.filename == filename);
if (screenshot != null)
{
screenshot.isPublic = val;
_dbContext.SaveChanges();
}
}
public void SomeMethod()
{
SomeEntity1 s1 = new SomeEntity1() { field1="fff", field2="aaa" };
_dbContext.SomeEntity1.Add(s1);
SomeEntity2 s2 = new SomeEntity2() { SE1 = s1 };
_dbContext.SomeEntity1.Add(s2);
_dbContext.SaveChanges();
}
And some external code create DBRepository object and call methods.
It worked fine. But now Async operations came in. So, if I use code like
public async void AddStatSimplePageAsync(string IPAddress, string login, string txt)
{
DateTime dateAdded2MinsAgo = DateTime.Now.AddMinutes(-2);
if ((from i in _dbContext.StatSimplePages where i.page == txt && i.dateAdded > dateAdded2MinsAgo select i).Count() == 0)
{
StatSimplePage item = new StatSimplePage() { IPAddress = IPAddress, login = login, page = txt, dateAdded = DateTime.Now };
_dbContext.StatSimplePages.Add(item);
await _dbContext.SaveChangesAsync();
}
}
can be a situation, when next code will be executed before SaveChanged completed and one more entity will be added to _dbContext, which should not be saved before some actions. For example, some code:
DBRepository _rep = new DBRepository();
_rep.AddStatSimplePageAsync("A", "b", "c");
_rep.SomeMethod();
I worry, that SaveChanged will be called after line
_dbContext.SomeEntity1.Add(s1);
but before
_dbContext.SomeEntity2.Add(s2);
(i.e. these 2 actions is atomic operation)
Am I right? My approach is wrong now? Which approach should be used?
PS. As I understand, will be the following stack:
1. calling AddStatSimplePageAsync
2. start calling await _dbContext.SaveChangesAsync(); inside AddStatSimplePageAsync
3. start calling SomeMethod(), _dbContext.SaveChangesAsync() in AddStatSimplePageAsync is executing in another (child) thread.
4. complete _dbContext.SaveChangesAsync() in child thread. Main thread is executing something in SomeMethod()
Ok this time I (think)'ve got your problem.
At first, it's weird that you have two separate calls to SaveChangesmethod. Usually you should try to have it at the end of all your operations and then dispose it.
Even thought yes, your concerns are right, but some clarifications are needed here.
When encountering an asyncor await do not think about threads, but about tasks, that are two different concepts.
Have a read to this great article. There is an image that will practically explain you everything.
To say that in few words, if you do not await an async method, you can have the risk that your subsequent operation could "harm" the execution of the first one. To solve it, simply await it.
Related
I'm fairly new to databases and asynchronous programing. I'm making a POS app that will eventually have hundreds of customers and possibly thousands of transactions. When I want to do a customer search or look up a previous ticket I don't want my program to hang waiting on the results.
Here is the method that shows the search result:
private void searchCritiria_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args)
{
FilteredCustomer.Clear();
if(searchCritiria.Text.Length >= 3)
{
SQLiteConnection dbConnection = new SQLiteConnection("Customers.db");
string sSQL = null;
sSQL = #"SELECT [first],[last],[spouse],[home],[work],[cell] FROM Customers";
ISQLiteStatement dbState = dbConnection.Prepare(sSQL);
while (dbState.Step() == SQLiteResult.ROW)
{
string sFirst = dbState["first"] as string;
string sLast = dbState["last"] as string;
string sSpouse = dbState["spouse"] as string;
string sHome = dbState["home"] as string;
string sWork = dbState["work"] as string;
string sCell = dbState["cell"] as string;
//Load into observable collection
if (searchType.SelectedIndex == 0)//name search
{
if(sFirst.Contains(searchCritiria.Text) || sLast.Contains(searchCritiria.Text) || sSpouse.Contains(searchCritiria.Text))
FilteredCustomer.Add(new Customer {first = sFirst, last = sLast, spouse = sSpouse, home = sHome, work = sWork, cell = sCell});
}
else//number search
{
if(sWork.Contains(searchCritiria.Text)|| sHome.Contains(searchCritiria.Text) || sCell.Contains(searchCritiria.Text))
FilteredCustomer.Add(new Customer { first = sFirst, last = sLast, spouse = sSpouse, home = sHome, work = sWork, cell = sCell });
}
}
}
}
Throughout my program I have void methods that are structured similar to this.
I'm not sure how to solve this issue. I tried doing some research but no success. Any advice would be greatly appreciated!
Edit
As correctly pointed out by #AndriyK, the answer would not have made your code asynchronous.
What it means:
Although the code works and you're able to push in data, if in case you reach a condition where two threads are trying to write into the database (Database is Locked condition, your application would still freeze until the database is not locked anymore or it times out. This means any loaders running would also freeze.
Making it asynchronous
To do so, you must run your SQLite code in a Task.Run() block. This would ensure your database runs on a different Thread and ensure your UI would never hang. This would also allow you to show ProgressRing (or other loaders) to the user while the application waits for the database to unlock. Below is the code:
public void PerformSQLTasks()
{
// your SQL code code here!
}
and run the above code by using:
Task.Run(() => PerformSQLTasks());
// or even
Task.Run(PerformSQLTasks);
Accepted Answer:
To make your UI not hang, you can make your method return a Task instead of void to make it awaitable. This will not make your code async but would allow the caller to await this method completion. To achieve this, follow the method signature below:
public Task PerformSQLTasks()
{
// your code here!
return Task.CompletedTask;
}
and you can call it by:
private async void searchCritiria_TextChanging(TextBox sender, TextBoxTextChangingEventArgs args)
{
await PerformSQLTasks();
}
Remember this won't make your code Asynchronous
I'm trying to run a unit test for a Update method in a DAO (EmployeeDAO.cs) inside my DAL layer/project. Inside the EmployeeDAO.cs class, my Update method
public UpdateStatus Update(Employee emp)
{
UpdateStatus status = UpdateStatus.Failed;
HelpdeskRepository repo = new HelpdeskRepository(new DbContext());
try
{
DbContext ctx = new DbContext();
var builder = Builders<Employee>.Filter;
var filter = Builders<Employee>.Filter.Eq("Id", emp.Id) & Builders<Employee>.Filter.Eq("Version", emp.Version);
var update = Builders<Employee>.Update
.Set("DepartmentId", emp.DepartmentId)
.Set("Email", emp.Email)
.Set("Firstname", emp.Firstname)
.Set("Lastname", emp.Lastname)
.Set("Phoneno", emp.Phoneno)
.Set("Title", emp.Title)
.Inc("Version", 1);
var result = ctx.Employees.UpdateOne(filter, update);
status = repo.Update(emp.Id.ToString(), filter, update);
//ask how to get status to work in MatchedCount/Modified count so we don't need DbContext use
if (result.MatchedCount == 0) //if zero version didn't match
{
status = UpdateStatus.Stale;
}
else if (result.ModifiedCount == 1)
{
status = UpdateStatus.Ok;
}
else
{
status = UpdateStatus.Failed;
}
}
catch (Exception ex)
{
DALUtils.ErrorRoutine(ex, "EmployeeDAO", "UpdateWithRepo");
}
return status;
}
appears to work fine, with no bugs being detected by the compiler. However, when I try to do some unit testing on it in this method inside my EmployeeDAOTests.cs/UnitTestProject inside the same solution,
[TestMethod]
public void TestUpdateShouldReturnOK()
{
EmployeeDAO dao = new EmployeeDAO();
Employee emp = dao.GetById(eid);
emp.Phoneno = "(555)555-9999";
Assert.IsTrue(dao.Update(emp) == UpdateStatus.OK);
}
it tells me that
(CS0117)"'UpdateStatus' does not contain a definition for 'OK'"
, which can be seen here to quite obviously have a definition for OK that appears to be valid for use in my actual DAO:
public enum UpdateStatus
{
Ok = 1,
Failed = -1,
Stale = -2
};
And on another note, when I trade the order in which I define Ok, Failed, and Stale around, it stops causing Unit Testing errors but begins to cause DAO errors!
Very confusing, anybody have any input?
It was a small case mistake :) UpdateStatus.OK should be UpdateStatus.Ok :)
I'm using hangfire 1.5.3. In my recurring job I want to call a service that uses the time since the last run. Unfortunately the LastExecution is set to the current time, because the job data was updated before executing the job.
Job
public abstract class RecurringJobBase
{
protected RecurringJobDto GetJob(string jobId)
{
using (var connection = JobStorage.Current.GetConnection())
{
return connection.GetRecurringJobs().FirstOrDefault(p => p.Id == jobId);
}
}
protected DateTime GetLastRun(string jobId)
{
var job = GetJob(jobId);
if (job != null && job.LastExecution.HasValue)
{
return job.LastExecution.Value.ToLocalTime();
}
return DateTime.Today;
}
}
public class NotifyQueryFilterSubscribersJob : RecurringJobBase
{
public const string JobId = "NotifyQueryFilterSubscribersJob";
private readonly IEntityFilterChangeNotificationService _notificationService;
public NotifyQueryFilterSubscribersJob(IEntityFilterChangeNotificationService notificationService)
{
_notificationService = notificationService;
}
public void Run()
{
var lastRun = GetLastRun(JobId);
_notificationService.CheckChangesAndSendNotifications(DateTime.Now - lastRun);
}
}
Register
RecurringJob.AddOrUpdate<NotifyQueryFilterSubscribersJob>(NotifyQueryFilterSubscribersJob.JobId, job => job.Run(), Cron.Minutely, TimeZoneInfo.Local);
I know, that it is configured as minutely, so I could calculate the time roughly. But I'd like to have a configuration independent implementation. So my Question is: How can I implement RecurringJobBase.GetLastRun to return the time of the previous run?
To address my comment above, where you might have more than one type of recurring job running but want to check previous states, you can check that the previous job info actually relates to this type of job by the following (although this feels a bit hacky/convoluted).
If you're passing the PerformContext into the job method than you can use this:
var jobName = performContext.BackgroundJob.Job.ToString();
var currentJobId = int.Parse(performContext.BackgroundJob.Id);
JobData jobFoundInfo = null;
using (var connection = JobStorage.Current.GetConnection()) {
var decrementId = currentJobId;
while (decrementId > currentJobId - 50 && decrementId > 1) { // try up to 50 jobs previously
decrementId--;
var jobInfo = connection.GetJobData(decrementId.ToString());
if (jobInfo.Job.ToString().Equals(jobName)) { // **THIS IS THE CHECK**
jobFoundInfo = jobInfo;
break;
}
}
if (jobFoundInfo == null) {
throw new Exception($"Could not find the previous run for job with name {jobName}");
}
return jobFoundInfo;
}
You could take advantage of the fact you already stated - "Unfortunately the LastExecution is set to the current time, because the job data was updated before executing the job".
The job includes the "LastJobId" property which seems to be an incremented Id. Hence, you should be able to get the "real" previous job by decrement LastJobId and querying the job data for that Id.
var currentJob = connection.GetRecurringJobs().FirstOrDefault(p => p.Id == CheckForExpiredPasswordsId);
if (currentJob == null)
{
return null; // Or whatever suits you
}
var previousJob = connection.GetJobData((Convert.ToInt32(currentJob.LastJobId) - 1).ToString());
return previousJob.CreatedAt;
Note that this is the time of creation, not execution. But it might be accurate enough for you. Bear in mind the edge case when it is your first run, hence there will be no previous job.
After digging around, I came up with the following solution.
var lastSucceded = JobStorage.Current.GetMonitoringApi().SucceededJobs(0, 1000).OrderByDescending(j => j.Value.SucceededAt).FirstOrDefault(j => j.Value.Job.Method.Name == "MethodName" && j.Value.Job.Type.FullName == "NameSpace.To.Class.Containing.The.Method").Value;
var lastExec = lastSucceded.SucceededAt?.AddMilliseconds(Convert.ToDouble(-lastSucceded.TotalDuration));
It's not perfect but i think a little cleaner than the other solutions.
Hopefully they will implement an official way soon.
The answer by #Marius Steinbach is often good enough but if you have thousands of job executions (my case) loading all of them from DB doesn't seem that great. So finally I decided to write a simple SQL query and use it directly (this is for PostgreSQL storage though changing it to SqlServer should be straightforward):
private async Task<DateTime?> GetLastSuccessfulExecutionTime(string jobType)
{
await using var conn = new NpgsqlConnection(_connectionString);
if (conn.State == ConnectionState.Closed)
conn.Open();
await using var cmd = new NpgsqlCommand(#"
SELECT s.data FROM hangfire.job j
LEFT JOIN hangfire.state s ON j.stateid = s.id
WHERE j.invocationdata LIKE $1 AND j.statename = $2
ORDER BY s.createdat DESC
LIMIT 1", conn)
{
Parameters =
{
new() { Value = $"%{jobType}%" } ,
new() { Value = SucceededState.StateName }
}
};
var result = await cmd.ExecuteScalarAsync();
if (result is not string data)
return null;
var stateData = JsonSerializer.Deserialize<Dictionary<string, string>>(data);
return JobHelper.DeserializeNullableDateTime(stateData?.GetValueOrDefault("SucceededAt"));
}
Use this method that return Last exucution time and Next execution time of one job. this method return last and next execution time of one job.
public static (DateTime?, DateTime?) GetExecutionDateTimes(string jobName)
{
DateTime? lastExecutionDateTime = null;
DateTime? nextExecutionDateTime = null;
using (var connection = JobStorage.Current.GetConnection())
{
var job = connection.GetRecurringJobs().FirstOrDefault(p => p.Id == jobName);
if (job != null && job.LastExecution.HasValue)
lastExecutionDateTime = job.LastExecution;
if (job != null && job.NextExecution.HasValue)
nextExecutionDateTime = job.NextExecution;
}
return (lastExecutionDateTime, nextExecutionDateTime);
}
Within an ASP.NET MVC Application I'm recieving the following error message for one of my controller methods that uses my Entity Framework context.
A second operation started on this context before a previous asynchronous operation completed. Use 'await' to ensure that any asynchronous operations have completed before calling another method on this context. Any instance members are not guaranteed to be thread safe.
I'm aware that you cannot run queries in parallel, and everything appears to be awaited properly. If I debug the program and step and inspect some of the data returned from EF then it works, probably because this forces the queries to complete.
EDIT If I place a breakpoint at the null check in the controller method and inspect the data of shipmentDetail the exception is NOT thrown.
Here's a snippit of the code:
Controller Method:
[Route("{id:int}/Deliveries")]
public async Task<ActionResult> DeliveryInfo(int id)
{
var shipmentDetail = await db.ShipmentDetails.SingleOrDefaultAsync(s => s.Id == id);
if (shipmentDetail == null)
return HttpNotFound(string.Format("No shipment detail found with id {0}", id));
var model = await DeliveryInfoModel.CreateModel(db, shipmentDetail);
return View("DeliveryInfo", model);
}
CreateModel Method:
public static async Task<DeliveryInfoModel> CreateModel(Context db, ShipmentDetail shipment)
{
DeliveryInfoModel model = new DeliveryInfoModel()
{
ShipmentInfo = shipment
};
//initialize processing dictionary
Dictionary<int, bool> boxesProcessed = new Dictionary<int, bool>();
List<DeliveryBoxStatus> statuses = new List<DeliveryBoxStatus>();
for (int i = 1; i <= shipment.BoxCount; i++ )
{
boxesProcessed.Add(i, false);
}
//work backwards through process
//check for dispositions from this shipment
if(shipment.Dispositions.Count > 0)
{
foreach (var d in shipment.Dispositions)
{
DeliveryBoxStatus status = new DeliveryBoxStatus()
{
BoxNumber = d.BoxNumber,
LastUpdated = d.Date,
Status = d.Type.GetDescription().ToUpper()
};
statuses.Add(status);
boxesProcessed[d.BoxNumber] = true;
}
}
//return if all boxes have been accounted for
if (boxesProcessed.Count(kv => kv.Value) == shipment.BoxCount)
{
model.BoxStatuses = statuses;
return model;
}
//check for deliveries
if(shipment.Job_Detail.Count > 0)
{
foreach (var j in shipment.Job_Detail.SelectMany(d => d.DeliveryInfos))
{
DeliveryBoxStatus status = new DeliveryBoxStatus()
{
BoxNumber = j.BoxNumber,
LastUpdated = j.Job_Detail.To_Client.GetValueOrDefault(),
Status = "DELIVERED"
};
statuses.Add(status);
boxesProcessed[j.BoxNumber] = true;
}
}
//check for items still in processing & where
foreach (int boxNum in boxesProcessed.Where(kv => !kv.Value).Select(kv => kv.Key))
{
//THIS LINE THROWS THE EXCEPTION
var processInfo = await db.Processes.Where(p => p.Jobs__.Equals(shipment.Job.Job__, StringComparison.InvariantCultureIgnoreCase) && p.Shipment == shipment.ShipmentNum && p.Box == boxNum)
.OrderByDescending(p => p.date)
.FirstOrDefaultAsync();
//process returned data
//...
}
model.BoxStatuses = statuses;
return model;
}
I'm not completely sure if it's because of the query made in the controller, or because of the queries made in the loop that aren't completing causing this behavior. Is there something I'm not understanding about when the queries are actually made/returned due to EF's laziness, or how async/await works in this situation? I have a lot of other methods & controllers that make async EF calls and haven't run into this previously.
EDIT
My context is injected into my controller using Ninject as my IoC container. Here's its config inside of NinjectWebCommon's RegisterServices method:
kernel.Bind<Context>().ToSelf().InRequestScope();
Avoid lazy loading when using async with Entity Framework. Instead, either load the data you need first, or use Include()'s to ensure the data you need is loaded with the query.
https://msdn.microsoft.com/en-gb/magazine/dn802603.aspx
Current State of Async Support
... Async
support was added to Entity Framework (in the EntityFramework NuGet
package) in version 6. You do have to be careful to avoid lazy
loading when working asynchronously, though, because lazy loading is
always performed synchronously. ...
(Emphasis mine)
Also:
https://entityframework.codeplex.com/wikipage?title=Task-based%20Asynchronous%20Pattern%20support%20in%20EF.#ThreadSafety
I have ported my old HttpHandler (.ashx) TwitterFeed code to a WebAPI application. The core of the code uses the excellent Linq2Twitter package (https://linqtotwitter.codeplex.com/). Part of the port involved upgrading this component from version 2 to version 3, which now provides a number of asynchronous method calls - which are new to me. Here is the basic controller:
public async Task<IEnumerable<Status>>
GetTweets(int count, bool includeRetweets, bool excludeReplies)
{
var auth = new SingleUserAuthorizer
{
CredentialStore = new SingleUserInMemoryCredentialStore
{
ConsumerKey = ConfigurationManager.AppSettings["twitterConsumerKey"],
ConsumerSecret = ConfigurationManager.AppSettings["twitterConsumerKeySecret"],
AccessToken = ConfigurationManager.AppSettings["twitterAccessToken"],
AccessTokenSecret = ConfigurationManager.AppSettings["twitterAccessTokenSecret"]
}
};
var ctx = new TwitterContext(auth);
var tweets =
await
(from tweet in ctx.Status
where (
(tweet.Type == StatusType.Home)
&& (tweet.ExcludeReplies == excludeReplies)
&& (tweet.IncludeMyRetweet == includeRetweets)
&& (tweet.Count == count)
)
select tweet)
.ToListAsync();
return tweets;
}
This works fine, but previously, I had cached the results to avoid 'over calling' the Twitter API. It is here that I have run into a problem (more to do with my lack of understanding of the asynchronous protocol than anything else I suspect).
In overview, what I want to do is to first check the cache, if data doesn't exists, then rehydrate the cache and return the data to the caller (web page). Here is my attempt at the code
public class TwitterController : ApiController {
private const string CacheKey = "TwitterFeed";
public async Task<IEnumerable<Status>>
GetTweets(int count, bool includeRetweets, bool excludeReplies)
{
var context = System.Web.HttpContext.Current;
var tweets = await GetTweetData(context, count, includeRetweets, excludeReplies);
return tweets;
}
private async Task<IEnumerable<Status>>
GetTweetData(HttpContext context, int count, bool includeRetweets, bool excludeReplies)
{
var cache = context.Cache;
Mutex mutex = null;
bool iOwnMutex = false;
IEnumerable<Status> data = (IEnumerable<Status>)cache[CacheKey];
// Start check to see if available on cache
if (data == null)
{
try
{
// Lock base on resource key
mutex = new Mutex(true, CacheKey);
// Wait until it is safe to enter (someone else might already be
// doing this), but also add 30 seconds max.
iOwnMutex = mutex.WaitOne(30000);
// Now let's see if some one else has added it...
data = (IEnumerable<Status>)cache[CacheKey];
// They did, so send it...
if (data != null)
{
return data;
}
if (iOwnMutex)
{
// Still not there, so now is the time to look for it!
data = await CallTwitterApi(count, includeRetweets, excludeReplies);
cache.Remove(CacheKey);
cache.Add(CacheKey, data, null, GetTwitterExpiryDate(),
TimeSpan.Zero, CacheItemPriority.Normal, null);
}
}
finally
{
// Release the Mutex.
if ((mutex != null) && (iOwnMutex))
{
// The following line throws the error:
// Object synchronization method was called from an
// unsynchronized block of code.
mutex.ReleaseMutex();
}
}
}
return data;
}
private DateTime GetTwitterExpiryDate()
{
string szExpiry = ConfigurationManager.AppSettings["twitterCacheExpiry"];
int expiry = Int32.Parse(szExpiry);
return DateTime.Now.AddMinutes(expiry);
}
private async Task<IEnumerable<Status>>
CallTwitterApi(int count, bool includeRetweets, bool excludeReplies)
{
var auth = new SingleUserAuthorizer
{
CredentialStore = new SingleUserInMemoryCredentialStore
{
ConsumerKey = ConfigurationManager.AppSettings["twitterConsumerKey"],
ConsumerSecret = ConfigurationManager.AppSettings["twitterConsumerKeySecret"],
AccessToken = ConfigurationManager.AppSettings["twitterAccessToken"],
AccessTokenSecret = ConfigurationManager.AppSettings["twitterAccessTokenSecret"]
}
};
var ctx = new TwitterContext(auth);
var tweets =
await
(from tweet in ctx.Status
where (
(tweet.Type == StatusType.Home)
&& (tweet.ExcludeReplies == excludeReplies)
&& (tweet.IncludeMyRetweet == includeRetweets)
&& (tweet.Count == count)
&& (tweet.RetweetCount < 1)
)
select tweet)
.ToListAsync();
return tweets;
}
}
The problem occurs in the finally code block where the Mutex is released (though I have concerns about the overall pattern and approach of the GetTweetData() method):
if ((mutex != null) && (iOwnMutex))
{
// The following line throws the error:
// Object synchronization method was called from an
// unsynchronized block of code.
mutex.ReleaseMutex();
}
If I comment out the line, the code works correctly, but (I assume) I should release the Mutex having created it. From what I have found out, this problem is related to the thread changing between creating and releasing the mutex.
Because of my lack of general knowledge on asynchronous coding, I am not sure a) if the pattern I'm using is viable and b) if it is, how I address the problem.
Any advice would be much appreciated.
Using a mutex like that isn't going to work. For one thing, a Mutex is thread-affine, so it can't be used with async code.
Other problems I noticed:
Cache is threadsafe, so it shouldn't need a mutex (or any other protection) anyway.
Asynchronous methods should follow the Task-based Asynchronous Pattern.
There is one major tip regarding caching: when you just have an in-memory cache, then cache the task rather than the resulting data. On a side note, I have to wonder whether HttpContext.Cache is the best cache to use, but I'll leave it as-is since your question is more about how asynchronous code changes caching patterns.
So, I'd recommend something like this:
private const string CacheKey = "TwitterFeed";
public Task<IEnumerable<Status>> GetTweetsAsync(int count, bool includeRetweets, bool excludeReplies)
{
var context = System.Web.HttpContext.Current;
return GetTweetDataAsync(context, count, includeRetweets, excludeReplies);
}
private Task<IEnumerable<Status>> GetTweetDataAsync(HttpContext context, int count, bool includeRetweets, bool excludeReplies)
{
var cache = context.Cache;
Task<IEnumerable<Status>> data = cache[CacheKey] as Task<IEnumerable<Status>>;
if (data != null)
return data;
data = CallTwitterApiAsync(count, includeRetweets, excludeReplies);
cache.Insert(CacheKey, data, null, GetTwitterExpiryDate(), TimeSpan.Zero);
return data;
}
private async Task<IEnumerable<Status>> CallTwitterApiAsync(int count, bool includeRetweets, bool excludeReplies)
{
...
}
There's a small possibility that if two different requests (from two different sessions) request the same twitter feed at the same exact time, that the feed will be requested twice. But I wouldn't lose sleep over it.