I have problem with Entity Core 3.1.2.
I have code like this:
SQL.Database.EnsureCreated();
var ThisCollector = SQL.CollectorServers
.Where(esa => esa.ServerName == ServerCollectorName)
.FirstOrDefault();
while (foo)
{
await SQL.Entry(ThisCollector)
.ReloadAsync();
DateTime dtTimeOut = DateTime.UtcNow.AddMinutes(-1);
//check status of current Worker
var CurrentLB = SQL.CollectorServers
.Where(esa => esa.isWorker == true
&& esa.LastSeenLB < dtTimeOut)
.FirstOrDefault();
if (CurrentLB!=null) //Current Worker is dead!
{
CurrentLB.isWorker = false;
ThisCollector.isWorker = true;
SQL.SaveChanges(); //This works allways
}
var Collectors = SQL.CollectorServers
.Where(Esa => Esa.isWorker == true);
if (Collectors.Count() == 0)
{
ThisCollector.isWorker = true;
SQL.SaveChanges();
}
if (Collectors.Count() >= 2)
{
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
//why this is requied?
SQL.Entry(cs).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
}
ThisCollector.isWorker = true;
//<--This works only once, without manually setting State to
// modified!!! Why? Values has been changed from external program.
//(Management studio in this case)
SQL.SaveChanges();
}
await Task.Delay(10000, stoppingToken);
}
Problem is that last SaveChanges works only first time it has been called without I set Entry state to Modified. After that it does not make SQL query (I can see that in SQL Profiler).
In this case this can be fixed by this way, but I'm trying to undestand why this happends. My software saves lot data to SQL, and I need to know can I trust to this code without opening all queries and adding this modified state.
I didin't have this kind of problems in full version (6) of Entity, this is something quite new for me.
The described behavior would make sense if the entities returned by CollectorServers are not tracked.
ThisCollector is attached on every loop by the call to SQL.Entry(ThisCollector) :
await SQL.Entry(ThisCollector) //Attaching
.ReloadAsync(); //Reloading
Any changes made to it would be tracked and saved by the first call to DbContext.SaveChanges().
On the other hand, the entities returned by the Collectors query :
var Collectors = SQL.CollectorServers
.Where(Esa => Esa.isWorker == true);
Would remain untracked, until they get reattached by the call to SQL.Entry(cs) :
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
SQL.Entry(cs).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
}
That's equivalent to calling DbContext.Update to attach and set the state to Modified. Update is easier to read though :
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
SQL.Update(cs);
}
I am trying to query records from the DB using Entity Framework. I need to get the total count of records as well as the actual records. What is the best approach to do this
public IEnumerable<mFeedback> RetrieveAll(QueryOptions qOptions)
{
if (qOptions == null)
throw new ArgumentNullException(nameof(qOptions));
using (_db)
{
var feedback = _db.Feedbacks
.Where(f => f.isDeleted == false);
if (qOptions.GetCount)
qOptions.TotalRecordsCount = feedback.Count();
feedback = feedback.OrderBy(string.IsNullOrWhiteSpace(qOptions.Sort) ? nameof(eFeedback.CreatedDate) : qOptions.Sort)
.Skip(qOptions.Skip)
.Take(qOptions.PageSize);
return _mapper.Map<IEnumerable<eFeedback>, IEnumerable<mFeedback>>(feedback.ToList());
}
}
The current code i have is shown above. This produces 2 hits on the DB. Is there a better approach?
Thanks in advance
A newbie question. I am using EntityFramework 4.0. The backend database has a function that will return a subset of records based on time.
Example of working code is:
var query = from rx in context.GetRxByDate(tencounter,groupid)
select rx;
var result = context.CreateDetachedCopy(query.ToList());
return result;
I need to verify that a record does not exist in the database before inserting a new record. Before performing the "Any" filter, I would like to populate the context.Rxes with a subset of the larger backend database using the above "GetRxByDate()" function.
I do not know how to populate "Rxes" before performing any further filtering since Rxes is defined as
IQueryable<Rx> Rxes
and does not allow "Rxes =.. ". Here is what I have so far:
using (var context = new EnityFramework())
{
if (!context.Rxes.Any(c => c.Cform == rx.Cform ))
{
// Insert new record
Rx r = new Rx();
r.Trx = realtime;
context.Add(r);
context.SaveChanges();
}
}
I am fully prepared to kick myself since I am sure the answer is simple.
All help is appreciated. Thanks.
Edit:
If I do it this way, "Any" seems to return the opposite results of what is expected:
var g = context.GetRxByDate(tencounter, groupid).ToList();
if( g.Any(c => c.Cform == rx.Cform ) {....}
I have an issue implementing CCR with SQL. It seems that when I step through my code the updates and inserts I am trying to execute work great. But when I run through my interface without any breakpoints, it seems to be working and it shows the inserts, updates, but at the end of the run, nothing got updated to the database.
I proceeded to add a pause to my code every time I pull anew thread from my pool and it works... but that defeats the purpose of async coding right? I want my interface to be faster, not slow it down...
Any suggestions... here is part of my code:
I use two helper classes to set my ports and get a response back...
/// <summary>
/// Gets the Reader, requires connection to be managed
/// </summary>
public static PortSet<Int32, Exception> GetReader(SqlCommand sqlCommand)
{
Port<Int32> portResponse = null;
Port<Exception> portException = null;
GetReaderResponse(sqlCommand, ref portResponse, ref portException);
return new PortSet<Int32, Exception>(portResponse, portException);
}
// Wrapper for SqlCommand's GetResponse
public static void GetReaderResponse(SqlCommand sqlCom,
ref Port<Int32> portResponse, ref Port<Exception> portException)
{
EnsurePortsExist(ref portResponse, ref portException);
sqlCom.BeginExecuteNonQuery(ApmResultToCcrResultFactory.Create(
portResponse, portException,
delegate(IAsyncResult ar) { return sqlCom.EndExecuteNonQuery(ar); }), null);
}
then I do something like this to queue up my calls...
DispatcherQueue queue = CreateDispatcher();
String[] commands = new String[2];
Int32 result = 0;
commands[0] = "exec someupdateStoredProcedure";
commands[1] = "exec someInsertStoredProcedure '" + Settings.Default.RunDate.ToString() + "'";
for (Int32 i = 0; i < commands.Length; i++)
{
using (SqlConnection connSP = new SqlConnection(Settings.Default.nbfConn + ";MultipleActiveResultSets=true;Async=true"))
using (SqlCommand cmdSP = new SqlCommand())
{
connSP.Open();
cmdSP.Connection = connSP;
cmdSP.CommandTimeout = 150;
cmdSP.CommandText = "set arithabort on; " + commands[i];
Arbiter.Activate(queue, Arbiter.Choice(ApmToCcrAdapters.GetReader(cmdSP),
delegate(Int32 reader) { result = reader; },
delegate(Exception e) { result = 0; throw new Exception(e.Message); }));
}
}
where ApmToCcrAdapters is the class name where my helper methods are...
The problem is when I pause my code right after the call to Arbiter.Activate and I check my database, everything looks fine... if I get rid of the pause ad run my code through, nothing happens to the database, and no exceptions are thrown either...
The problem here is that you are calling Arbiter.Activate in the scope of your two using blocks. Don't forget that the CCR task you create is queued and the current thread continues... right past the scope of the using blocks. You've created a race condition, because the Choice must execute before connSP and cmdSP are disposed and that's only going to happen when you're interfering with the thread timings, as you have observed when debugging.
If instead you were to deal with disposal manually in the handler delegates for the Choice, this problem would no longer occur, however this makes for brittle code where it's easy to overlook disposal.
I'd recommend implementing the CCR iterator pattern and collecting results with a MulitpleItemReceive so that you can keep your using statements. It makes for cleaner code. Off the top of my head it would look something like this:
private IEnumerator<ITask> QueryIterator(
string command,
PortSet<Int32,Exception> resultPort)
{
using (SqlConnection connSP =
new SqlConnection(Settings.Default.nbfConn
+ ";MultipleActiveResultSets=true;Async=true"))
using (SqlCommand cmdSP = new SqlCommand())
{
Int32 result = 0;
connSP.Open();
cmdSP.Connection = connSP;
cmdSP.CommandTimeout = 150;
cmdSP.CommandText = "set arithabort on; " + commands[i];
yield return Arbiter.Choice(ApmToCcrAdapters.GetReader(cmdSP),
delegate(Int32 reader) { resultPort.Post(reader); },
delegate(Exception e) { resultPort.Post(e); });
}
}
and you could use it something like this:
var resultPort=new PortSet<Int32,Exception>();
foreach(var command in commands)
{
Arbiter.Activate(queue,
Arbiter.FromIteratorHandler(()=>QueryIterator(command,resultPort))
);
}
Arbiter.Activate(queue,
Arbiter.MultipleItemReceive(
resultPort,
commands.Count(),
(results,exceptions)=>{
//everything is done and you've got 2
//collections here, results and exceptions
//to process as you want
}
)
);
I am having a real issue with the EF v1. I have quite a big EDMX with maybe 50 entities mapped, but this one entity is causing me grief.
The entity has mappings to other entities which in effect are reference tables, but for some reason it is trying to do an insert and not just update itself.
Here is a fragment of my code:
using (var context = new someEntities()) {
var studentCourseJoin =
context.StudentCourseJoinSet.Where(o => o.Code == scjCode).First();
studentCourseJoin.EntryStatus = new EntryStatus { Code = viewModel.StudentDetails.EntryStatusCode };
studentCourseJoin.ParentalInHigherEducation = new ParentalInHigherEducation { Code = viewModel.StudentDetails.ParentalInHigherEducationCode };
studentCourseJoin.School = new School { Code = viewModel.StudentDetails.SchoolCode };
studentCourseJoin.Institution = new Institution { Code = viewModel.StudentDetails.InstitutionCode };
studentCourseJoin.LastSchoolEndYear = viewModel.StudentDetails.LastSchoolEndYear;
studentCourseJoin.LastInstitutionEndYear = viewModel.StudentDetails.LastInstitutionEndYear;
// Blows up here trying to do an insert on the studentCourseJoin.Institution.
// But if I removed this one, then it will blow up on another one.
context.SaveChanges(true);
}
If anyone has ANY ideas please, they would help a lot.
Try adding those lines before calling SaveChanges:
ObjectStateEntry entry = context.ObjectStateManager.GetObjectStateEntry(studentCourseJoin);
entry.ChangeState(EntityState.Modified);
Update:
Try this for Institution instead:
studentCourseJoin.Institution = context.Institutions.FirstOrDefault(i => i.Code == viewModel.StudentDetails.InstitutionCode);