I'm trying to get the latest forum threads in my forum, just like this:
var threads = _context.Threads.Include(x => x.User).OrderByDescending(x => x.CreateDate).Take(3).ToList();
However, this gives me the following exception:
There is already an open DataReader associated with this Connection which must be closed first.
Before I load these threads, I am loading some settings, like this:
var frontPageSettings = _context.Settings.FirstOrDefault(x => x.Key == Constants.SettingsKeys.FrontPageSettings.ToString());
Could this be the issue?
I have absolutely no idea what is happening, or how to get around it. Any guidance towards a solution is highly appreciated.
If you need more information such as stack trace, please let me know.
EXTRA INFO
I'm using Entity Framework for MariaDB (MySQL) and ASP.NET Core
EDIT
If I remove my .Include(x => x.User), the exception disappears, so I believe this has something to do with the include
Related
This is my very first attempt to work with Xamarin studio with Realm (to make app for both iOS and Android) and I am stuck at this situation since last 24 hours.
My online database-table has 30,000 rows. Earlier when I used to work in Android studio, I used to import those rows in app's 1st run with the help of JSON, GSON and insert into SQLite db.
But I am unable to do so in Realm & Xamarin. I know, I have not provided any code snippet (my effort), but honestly even after searching a lot about this, I couldn't find how should I proceed?
I've already answered that in the Github issue, but in case someone else stumbles across it, the best way to do that without blocking the UI thread, is to use the Realm.WriteAsync API. Basically, you'll do something like:
var items = await service.GetAllItems();
// I assume items are already deserialized RealmObject-s
var realm = Realm.GetInstance();
await realm.WriteAsync(r =>
{
foreach (var item in items)
{
r.Manage(item);
}
}
/* Data is loaded, show message or process it in other ways */
One thing to note is that within the WriteAsync lambda, we're using the r instance and not the original realm one. The reason is that because realms are not thread safe and the asynchronous write will happen on another thread, so it implicitly creates another instance and passes it as an argument of the action parameter.
I am attempting to read the output of an SSIS Data Profile task into an MVC app. To work out the kinks, I wrote a small console app to test the parsing of the xml file.
I used the following link:
http://schemas.microsoft.com/sqlserver/2008/DataDebugger/DataProfile.xsd
to download the .XSD file that should describe the .XML file that was generated in the Data Profile output file.
I then ran xsd.exe to create a C# class to include in my console app.
Following is my very simple test code:
XmlSerializer xser = new XmlSerializer(typeof(DataProfile));
DataProfile dProf = xser.Deserialize(new FileStream(#"D:\InputFiles\ProfilerDataCVD.XML", FileMode.Open)) as DataProfile;
if (dProf != null)
{
var profs = dProf.DataProfileOutput.Profiles;
foreach (ColumnValueDistributionProfileType c in profs)
{
Console.WriteLine(string.Format("Column Name: {0}, RowCount: {1}, Distinct Values: {2}", c.Column.Name, c.Table.RowCount, c.NumberOfDistinctValues));
}
}
In that code, "dProf" is never NULL, but always empty. Any assistance at getting data in dProf would possibly save a life, because I am about to jump off of a cliff trying to figure this out!
If there is some obvious XML thing that I am missing, I will be the first to admit that this is not my strongest suit. Feel free to chastise me at will as long as you tell me how to make this return data.
Regrettably, no one has been able to answer this question. And I would still really like to understand why something so simple does not work.
In the meantime, anyone else struggling with the same issue should check out the following link on MSDN forums for an alternative way of doing the same thing.
http://social.msdn.microsoft.com/Forums/en-US/sqlintegrationservices/thread/a282bb60-c099-4656-bf71-52ddc6153c28
I implemented it yesterday in just a few minutes and it works great.
I've got a CakePHP application and I'm interested in reacting to a user's attempt to upload a file that's too large for the MySQL packet size. I'd like to get the MySQL error and then provide an error message to the user based on that.
It looks like CakePHP uses PDO under the hood, but I'm not sure how to access it. I'd rather borrow CakePHP's PDO connection so that I don't have to create a new PDO connection w/ the username, password, etc, etc (also so I don't have to worry about problems from multiple connections to the same DB, etc).
It looks like there's a PDO class in CakePHP (http://api.cakephp.org/2.2/class-PDO.html), but I'm not sure how to actually get to it in order to invoke the errorCode() method.
This is the method you probably need. In your controller after a save operation you can use $this->SomeModel->getDataSource()->lastError() to get the error.
Or.... check this out:
if( is_a( $this->SomeModel->getDataSource(), "DboSource") ) {
$myPDO = $this->SomeModel->getDataSource()->getConnection();
debug($myPDO.errorCode()); // or whatever...
}
Anyways, thanks a ton for your help with this - there was just a couple too many hops in the documentation for me to find this on my own.
(I'm posting this here instead of as a comment to your answer so that it'll stand out better)
I created WPF application using c#.I have to get more data in here from mysql databse.I'm use for this one ODBC 3.51 connector.when data loading freeze my application.
I'm try to fix that problem using thread.But I can't able to do this one using thread. Please suggest to way for solve my problem...
Use a BackgroundWorker-class. It's usage is very simple and it is used quite often for tasks such as loading data. The following example shows you it's usage:
BackgroundWorker bgWorker = new BackgroundWorker() { WorkerReportsProgress=true};
bgWorker.DoWork += (s, e) => {
// Load here your data
// Use bgWorker.ReportProgress(); to report the current progress
};
bgWorker.ProgressChanged+=(s,e)=>{
// Here you will be informed about progress and here it is save to change/show progress.
// You can access from here savely a ProgressBars or another control.
};
bgWorker.RunWorkerCompleted += (s, e) => {
// Here you will be informed if the job is done.
// Use this event to unlock your gui
};
bgWorker.RunWorkerAsync();
The use of the BackgroundWorker allows the UI-thread to continue it's processing and therefore the application rests responsive during loading. But because of this, you have also to ensure that no actions can take place that rely on the loaded data. A very simple solution is to set your main UI elements IsEnabled-property to false and in RunWorkerCompleted you set it to true. With a little fantasy you can improve this dumb behaviour tp a nice UI-experience (depending on the App).
It is general a good a advice to do long time operations in a separate thread (BackgroundWorker). One caveat is there: Do not create WPF-Elements in the DoWork-event. This will not do because all derived types of DependencyObject must be created in the same thread they are used.
There are other solutions to do this, for example creating directly a thread or with the event based async pattern, but I recommend to use BackgroundWorker for your task because it handels for you the plumbing. In the end, the result is the same but the way to it is much easier.
I've received an error report from a client recently and am having no luck resolving it. I'm hoping someone can give me some insight to what may be wrong.
The error seems simple enough:
Csla.DataPortalException: DataPortal.Delete failed (System.InvalidOperationException: Sequence contains more than one element at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
Here is my DataPortal_Delete method, which takes the FileId (PK) as a parameter.
private void DataPortal_Delete(SingleCriteria<File, Guid> criteria)
{
using (var ctx = ContextManager<Ronin.Data.RoninDataContext>
.GetManager(Database.ApplicationConnection, false))
{
var data = ctx.DataContext.Files
.Single(row => row.FileId == criteria.Value);
ctx.DataContext.FileSources.DeleteAllOnSubmit(data.FileSources);
ctx.DataContext.Files.DeleteOnSubmit(data);
ctx.DataContext.SubmitChanges();
}
}
First thing I check was to see if there was another record with the same FileId (although being the primary key, this should be impossible). All FileIds were in fact unique. I launched the application connecting to the client database and tried to delete the record and it worked without any issues. The IT guy at the client site used the "Problem Step Recorder" to send me step by step screenshots of the actions taken by the user. Nothing out of the ordinary, and when he used a different machine, he was able to delete the record without any errors. Apparently this only happens when the application is run in Windows 7.
That said, any ideas as to what could be causing this?
Assuming the call to Single is the source of the problem, instead of:
ctx.DataContext.Files.Single(...)
change the code to allow the return of multiple rows from that query and then log what it's returning when it returns more than one row. This should point you toward your "duplicate" data problem.
Another thing to look at is the SQL that is being generated behind the scenes. Not sure that will help, but it can't hurt. I don't know your data model, so I can't understand your code as well as I would like to.
If it only happens in Windows 7 then this might be cause by the OS. Have you tried it on Vista? Vista's environment is simmilar on Windows 7. You can also use Windows Virtual PC + XP Mode. This is a virtualization application specially designed for Windows 7 to let users run applications like they use to in Windows XP. Note: XP Mode requires virtualization capable processor.
I had the same exception when deleting one entity. The problem turned out to be a foreign key relation defined in the dbml-File. So this was the reason for the exception in my case.
After I removed that it worked to delete the record (and I didn't want to cascade delete the records from the other table, I just need to find out how to configurate linq-to-sql to just set the foreign key column to null)