Develop Reference

EFCore - How to run simple query on a loop?

I'm working on a project where users can queue up actions to happen in the future. Each future action is saved in the database. I'm trying to find a way to get all the actions that have already passed and act on them. Currently I'm doing this:
public class TaskingManager
{
private static readonly System.Timers.Timer RefreshEventsLoop = new(1000);
public void Initialize()
{
RefreshEventsLoop.Elapsed += RefreshEventsLoop_Elapsed;
RefreshEventsLoop.AutoReset = false;
RefreshEventsLoop.Start();
}
private void RefreshEventsLoop_Elapsed(object? sender, System.Timers.ElapsedEventArgs e)
{
RefreshEventsLoop.Enabled = false;
ProcessEventsQueue();
RefreshEventsLoop.Enabled = true;
}
private void ProcessEventsQueue()
{
var timeNow = DateTime.UtcNow;
var context = new GalaxyDbContext(_dbOptions);
var dbFunctions = new DatabaseFunctions(context);
var eventsToProcess = context.FutureEvents
.Where(futureEvent => futureEvent.TriggerTime <= timeNow)
.ToList();
if (eventsToProcess.Any())
{
context.FutureEvents.RemoveRange(eventsToProcess);
context.SaveChanges();
foreach (var pastEvent in eventsToProcess)
{
_messageMap[pastEvent.MessageType].Invoke(dbFunctions).Execute(pastEvent);
}
}
else
{
dbFunctions.CreateFutureScienceTask();
}
}
}
This seems to work ok. But the problem is that after the app has been running for a while, I can see the LINQ part is taking up a huge amount of memory:
524MB used
And if I leave it running for a few days then it's up in the gigs.
I'm guessing running this query every second is wasteful on resources. But I don't know of a better way to do this. Is there a way to continuously check the database for something like this?

The first thing i can see is that you are not disposing the databasecontextt afer you used it.
Read this for more info about entityframework context lifetime.
To properly dispose it use a using statement.
using (var context = new GalaxyDbContext(_dbOptions))
{
//your code that uses the context
}
Or with new using syntax:
using (var context = new GalaxyDbContext(_dbOptions));
//your code that uses the context
Right know the problem could be that you create a context everytime you call the function and never dispose it and it still keeps references to the data etc..

NSubstitute Async returns null despite defined return object

I have a unit test that should return the specified object but it is returning null.
The Data Provider to test:
public class PlanDataProvider : BaseDomainServiceProvider, IPlanDataProvider
{
//CTOR
public PlanDataProvider(IDataAccessTemplate template, IEntityStore entityStore) : base(template, entityStore)
{
}
public async Task<DefaultActionPlan> GetDefaultActionPlan(string referenceListId)
{
var objectId = GetObjectId(referenceListId);
var defaultActionPlan = await Template.InvokeAsync(context => Task.FromResult(EntityStore.GetEntityById<DefaultActionPlan, ObjectId>
(
context.ActivityContext as IDataAccessContext,
typeof(DefaultActionPlan).FullName,
objectId
)));
}
}
The Test:
public async Task GetPlan_BadPlanID()
{
//Arrange
string badPlanId = "57509afbc6b48d3f33b2dfcd";
...snip...
DefaultActionPlan jj = new ObjectId(badPlanId);
//create EntityStore object
var dataxs = Substitute.For<IDataAccessContext>();
var estore = Substitute.For<IEntityStore>();
estore.GetEntityById<DefaultActionPlan, ObjectId>(
dataxs,
typeof(DefaultActionPlan).FullName,
new ObjectId(badPlanId))
.Returns(Task.FromResult(jj).Result);
var dataAccessTemplate = Substitute.For<IDataAccessTemplate>();
PlanDataProvider pdp = new PlanDataProvider(dataAccessTemplate, estore);
//Act
var t = await pdp.GetDefaultActionPlan(badPlanId);
//Now this confuses me as the compiler thinks t is DefaultActionPlan NOT Task<DefaultActionPlan>???
}
Anyway t returns null eferytime and debugging the test t is null because the GetDefaultActionPlan is not returning jj but instead null??
What am I missing to have jj returned?
Edit:
Both Eris and Gabe rightly pointed out that my Mock of the IEntityStore was not sufficient as that value...even though it specifies a return will not get passed to the wrapping InvokeAsync thus I needed to Mock the InvokeAsync as well.
Gabe's answer was slightly off as passing Arg.Any does not satisfy the InvokeAsync needed parms. However I do not fault him for this as I spent an hours tracking the inheritance chain across multiple projects (this is a big company). Something he does not have access to do.
In the end here is the code that resulted in success:
var estore = Substitute.For<IEntityStore>();
var dataAccessTemplate = Substitute.For<IDataAccessTemplate>();
dataAccessTemplate.InvokeAsync(context => Task.FromResult(
estore.GetEntityById<DefaultActionPlan>(
dataxs, typeof(DefaultActionPlan).FullName, new ObjectId(badPlanId))))
.ReturnsForAnyArgs(jj);
var pdp = new PlanDataProvider(dataAccessTemplate, estore);

While I don't see this in your code, I will assume that GetDefaultActionPlan returns the defaultActionPlan variable, and that Template.InvokeAsync is referring to the IDataAccessTemplate passed in via the constructor.
It looks like you are missing a mock return value for Template.InvokeAsync, and since it is wrapping the other call its return value is the only one you care about:
var estore = Substitute.For<IEntityStore>();
var dataAccessTemplate = Substitute.For<IDataAccessTemplate>();
dataAccessTemplate.InvokeAsync(context => Task.FromResult(Arg.Any<DefaultActionPlan>)
.ReturnsForAnyArgs(jj);
var pdp = new PlanDataProvider(dataAccessTemplate, estore);

Find usages of method group syntax in solution

I am trying to identify usages of the "method group" syntax in my solution. The reason is that Resharper tries to help with the ConvertClosureToMethodGroup code inspection. The problem is, that the "optimized" code does not compile to the same IL code, which means that it breaks in my specific scenario. The below scenario does not break, but it illustrates what I am trying to find:
void Main()
{
var arr = new string[]{"foo"};
//This works
var bar = arr.Select(s=>MyMethod(s));
//Resharper suggests the below, which is different
//var bar = arr.Select(MyMethod);
}
string MyMethod(string s)
{
return "bar";
}
So: Is there a way, that I can identify all the places in my code, where any method is being passed as a method group?
I can disable the refactoring suggestion to prevent future usages of this, but how can I identify the places where this already happened?
EDIT 1: Example where this refactoring breaks runtime
void Main()
{
MyClass obj = null;
//This works
var lazy = new Lazy<bool>(()=> obj.MyMethod());
//This will break at runtime when obj is null
//var lazy = new Lazy<bool>(obj.MyMethod);
}
class MyClass
{
public bool MyMethod()
{
return false;
}
}

Instantiate a class in a separate thread without a compile time warning

Is it possible to instantiate a class in a separate thread without a compile time warning?
For example the below code gives the compile time error "Use of unassigned local variable BECheck". I would rather keep AvailabilityCheckBase abstract and not assign it some dummy variable. Creating both BTCheck and BECheck is slow which is why I need it threaded.
public static AvailabilityCheckBase ByDSL(string dsl)
{
AvailabilityCheckBase BECheck;
AvailabilityCheckBase BTCheck;
Thread BEThread = new Thread(new ThreadStart(() => BECheck = new BEAvailabilityCheck(dsl)));
Thread BTThread = new Thread(new ThreadStart(() => BTCheck = new BTAvailabilityCheck(dsl)));
BEThread.Join();
BTThread.Join();
return BECheck.Merge(BTCheck);
}

The language has no knowledge of the Thread constructor or the Join method: it can't tell that you will definitely assign values to both variables before Join returns. If you want to keep the current approach, you'll need to assign values to the variables first. I agree this is slightly ugly, but it's the only way of keeping the compiler happy here.
(It's not clear why you're creating two new threads here, given that your original thread is then blocking on both of them, by the way.)
A better approach if you're using .NET 4 would be to use Task<T>, which effectively gives you the "promise" of a value:
Task<AvailabilityCheckBase> beCheck =
Task.Factory.StartNew(() => new BEAvailabilityCheck(dsl));
Task<AvailabilityCheckBase> btCheck =
Task.Factory.StartNew(() => new BTAvailabilityCheck(dsl));
return beCheck.Result.Merge(btCheck.Result);
It's worth becoming familiar with Task<T> and the TPL in general, as the new async features in C# 5 are heavily dependent on them.

Doesn't this fix your compile error? :
change
AvailabilityCheckBase BECheck;
AvailabilityCheckBase BTCheck;
to
AvailabilityCheckBase BECheck = null;
AvailabilityCheckBase BTCheck = null;

In order to call BECheck.Merge in your last line, BECheck should be initialized, and the compiler doesn't know it will be created before Thread.Join.
Try writing
AvailabilityCheckBase BECheck = null;
AvailabilityCheckBase BTCheck = null;
in the first lines.

If you assign the values to null you should see the message disappear, this would be good practice. There also doesn't appear to be any checking to make sure that the initialisations worked, you should probably include a check for BECheck and BTCheck still being null at the end of the function before you try to return to avoid an exception being thrown.

Use Task's:
Task<AvailabilityCheckBase> BETask = new Task<AvailabilityCheckBase>(() => BECheck = new BEAvailabilityCheck(dsl));
Task<AvailabilityCheckBase> BTTask = new Task<AvailabilityCheckBase>(() => BECheck = new BTAvailabilityCheck(dsl));
BETask.WaitAll(BETask,BTTask);
AvailabilityCheckBase BECheck = BETask.Result;
AvailabilityCheckBase BTCheck = BTTask.Result;

Locking with Constructors causing Null Reference?

So I encountered a strange issue today - I had a simple creation of an instance inside the critical section of a lock, and it would throw a null reference exception when I manually dragged the next line to execute. To illustrate:
public class SearchEngineOptimizationParser
{
protected static ConcurrentDictionary<string, SearchEngineOptimizationInfo> _referralInformation = null;
protected static DateTime _lastRecordingDate;
protected static object _lockRecordingObject = new object();
protected static Dictionary<string, string> _searchProviderLookups = null;
static SearchEngineOptimizationParser()
{
_referralInformation = new ConcurrentDictionary<string, SearchEngineOptimizationInfo>();
_lastRecordingDate = DateTime.Now;
_searchProviderLookups = new Dictionary<string, string>();
_searchProviderLookups.Add("google.com", "q");
_searchProviderLookups.Add("yahoo.com", "p");
_searchProviderLookups.Add("bing.com", "q");
}
public SearchEngineOptimizationParser()
{
}
public virtual void ParseReferrer(Uri requestUrl, NameValueCollection serverVariables, ISession session)
{
string corePath = requestUrl.PathAndQuery.SmartSplit('?')[0].ToLower();
string referrer = serverVariables["HTTP_REFERER"];
if (!string.IsNullOrWhiteSpace(referrer))
{
NameValueCollection queryString = HttpUtility.ParseQueryString(referrer);
string dictionaryKey = session.AffiliateID + "|" + corePath;
foreach (var searchProvider in _searchProviderLookups)
{
if (referrer.Contains(searchProvider.Key))
{
if (queryString[searchProvider.Value] != null)
{
string keywords = queryString[searchProvider.Value];
SearchEngineOptimizationInfo info = new SearchEngineOptimizationInfo
{
Count = 1,
CorePath = corePath,
AffiliateId = session.AffiliateID,
Keywords = keywords
};
_referralInformation.AddOrUpdate(dictionaryKey, info, (key, oldValue) =>
{
oldValue.Count++;
return oldValue;
});
break;
}
}
}
}
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
lock (_lockRecordingObject)
{
if (DateTime.Now > _lastRecordingDate.AddHours(1))
{
SearchEngineKeywordRepository repository = new SearchEngineKeywordRepository();
List<KeyValuePair<string, SearchEngineOptimizationInfo>> currentInfo = _referralInformation.ToList();
Action logData = () =>
{
foreach (var item in currentInfo)
repository.LogKeyword(item.Value);
};
Thread logThread = new Thread(new ThreadStart(logData));
logThread.Start();
_lastRecordingDate = DateTime.Now;
_referralInformation.Clear();
}
}
}
}
EDIT: Updated Real Object
public class SearchEngineKeywordRepository
{
public virtual void LogKeyword(SearchEngineOptimizationInfo keywordInfo)
{
LogSearchEngineKeywords procedure = new LogSearchEngineKeywords();
procedure.Execute(keywordInfo.CorePath, keywordInfo.AffiliateId, keywordInfo.Keywords, keywordInfo.Count);
}
}
The general pattern being that I want to do this 'something' only every hour (in the context of a website application that gets a lot of traffic). I would breakpoint my first if statement, and then step the next line to execute inside the second if statement. When doing so, the act of initializing the SomeObject instance would cause a null reference exception. It had a completely 100% default constructor - I didn't even specify one.
However, when I let the code go through naturally, it would execute without problem. For some reason, it seems that when I skipped over the lock call into the critical section to just test run that code, it caused all kinds of errors.
I'm curious to know why that is; I understand the lock keyword is just syntactic sugar for a Monitor.Enter(o) try / finally block, but that seems to be that when invoking the constructor, something else was happening.
Anyone have any ideas?
EDIT: I've added the actual code to this. I'm able to reproduce this at will, but I still don't understand why this is happening. I've tried copying this code to another solution and the problem does not seem to occur.

I've tried to reproduce your situation, but as I expected I could not. I've tried both the 2.0 and 4.0 runtime, in 32 and 64 bit mode (debugging sometimes behaves differently under x64).
Is the code shown a simplification? Have you checked all your assumptions? I understand you're skipping 3 lines of code, both the if statements and the lock? In that case, even setting the lock object to null does not cause the exception you describe.
(Having _lockRecordingObject set to null causes an ArgumentNullException when leaving the lock scope)