I am having an odd problem with data loading which I don't understand, and I am hoping someone can explain to me what is going on, and perhaps how to accomplish my task more directly.
I am building a website using the technologies listed in the subject of this question.
I have a set of objects - each object has several properties (Name, ID, etc.) and a collection (ICollection<>) of other objects. So just looking at the tree of objects and their collections, it looks like this:
Tab
-TabRows
--Sections
---SectionRow
----Article
(So each tab has one or more tabrows, each tabrow has one or more sections, and so on. Each sub-object has a link back the parent, so each sectionrow has a SectionID, each Section has a TabRowID, etc.)
OK, so given that structure, consider this code:
// GET api/Tab/5
public Tab GetTab(int id)
{
var tab = db.Tabs.FirstOrDefault(t => t.TabId == id);
var tabrows = db.TabRows.ToList();
var sections = db.Sections.ToList(); // This makes the tabRow.Sections populate
var sectionrows = db.SectionRows.ToList();
var articles = db.Articles.ToList();
return tab;
}
So here is what happens. When the first line (var tab =...) executes, I get a tab object, but the TabRows collection is empty. (It is not null because the constructor instantiates it).
When the second line (var tabrows =...) executes, tab.TabRows suddenly populates. tab.TabRows.Sections is empty.
When the third line executes, tab.TabRows.Sections suddenly populates.
And so on.
I am assuming this is some sort of "lazy loading" on behalf of Linq, or perhaps one of the other technologies. But I don't know them well enough to figure it out.
Is there a way to re-write this so that I can just call line 1 and basically have everything auto-populate without having to individually reference every single object in every single collection?
Lazy loading is enabled by default and eager loading disabled. Entity framework allows you to hint at eager loading using the include statements. Your statement will become something like this.
var tab = db.Tabs.FirstOrDefault(t => t.TabId == id).Include("TabRows");
or as Include(t => t.TabRows);
Take a look at this link for more information.
In your case you would need to handle nested includes as well. Which means you would be better off taking another Model (your class) structured as follows
Tabs -> Containing a List<TabRows> -> containing a List<Sections> etc.
You would then need to re-write the linq so it populates the entire Model including the nested entities using nested includes.
As a side note, too many of these inner joins might slow down your querying and so consider indexed views on your DB side if and when possible
I am trying to read through the dataBind documentation, but it's not all that clear:
http://grails.org/doc/2.1.0/ref/Controllers/bindData.html
I have a composite id composed of 4 columns, and I need to update one of those. It refuses to .save() and doesn't even throw an error. Is there some configuration that will allow me to change these values and save the model?
If I delete it and create a new record, it will bump the rowid, which I was using on the browser side with datatables/jeditable, and it's not really an option. However, even if I include all the parameters with an empty list:
def a = WaiverExemption.find("from WaiverExemption as e where e.exemptionRowId = ?", [params.rowid])
a.properties = params
bindData(a, params, [include: []])
a.save(flush: true, failOnError: true)
This does not seem to work. I've also tried naming the columns/properties explicitly both by themselves and also with "id".
I was confused on what bindData() actually does. Still confused on that.
If you have a composite id in Grails and wish to change one or more of the column values, save() will never ever execute as suggested in the question. Instead, you'll want to use .executeUpdate(). You can pass in HQL that updates (though most of the examples on the web are for delete) the table in question, with syntax that is nearly identical to proper SQL. Something along the lines of "update domain d set d.propertyName = ?" should work.
I do not know if this is a wise thing to do, or if it violates some philosophical rule of how a Grails app should work, but it will actually do the update. I advise caution and plenty of testing. This crap's all voodoo to me.
I have entity User with a couple of one-to-one and many-to-many relations and Identity primary key, and generic repository which created on each request.
I have an registration form with client and server validation and i decided to turn off client validation to test how server would behave in such case.
I turned off client validation to test the registration form and put some invalid values so i get back form saying that i have some errors, after i fixed that i got very interesting error
saying:
_context.SaveChanges(); //towing the error below:
Conflicting changes detected. This may happen when trying to insert multiple entities with the same key
It was strange for me because i detached the entity User but when i found this How to clean-up an Entity Framework object context?
so instead detaching only User entity i decided to try to clean object context completely running that code:
var objectStateEntries = this.objectContext
.ObjectStateManager
.GetObjectStateEntries(EntityState.Added);
foreach (var objectStateEntry in objectStateEntries)
{
if(objectStateEntry.Entity != null)
this.objectContext.Detach(objectStateEntry.Entity);
}
So after that all working well and i didn't get Conflicting changes detected error any more, but i am still wondering why such situation was taking place, may be some one may explain?
You may find your answer here:
context.ObjectStateManager.GetObjectStateEntries(System.Data.Entity.EntityState.Added| System.Data.Entity.EntityState.Unchanged);
I get System.NotSupportedException: An attempt has been made to Attach or Add an entity that is not new perhaps having been loaded from another DataContext when I want to update an object's with child entities.
The scenario is like this:
I have a SubscriberProvider that allows me to create subscribers.
var provider = new SubscriberProvider(); // Creates a new repository with own datacontext
var newSubscriber = new Subscriber
{
EmailAddress = emailAddress,
};
newSubscriber.Interests.Add(new Interest{
Id=1,
Name="cars"
});
provider.Subscribe(newSubscriber);
On a normal subscribe page, this works fine.
Now I have a linq2sql Member class(retrievable by a MemberRepository) and I want to extend it to have a helper subscribe method like so:
var repository = new MembershipRepository(); // Holds its own datacontext
var member = repository.Get("member1");
member.Subscribe(); // transfer member's info and interests to subscriber's table
The exception occurs when SubscriberProvider tries to add interests of the member.
Commenting out
newSubscriber.Interests.Add(new Interest{
Id=1,
Name="cars"
});
will make member.Subscribe() work.
member.Subscribe() is simply:
public void Subscribe(bool emailIsVerified, bool receiveEmails, bool sendDoubleOptIn)
{
var provider = new MailingListProvider();
provider.Subscribe(EmailAddress, emailIsVerified, receiveEmails, CountryId, sendDoubleOptIn, ConvertInterests(MemberInterests.ToList()));
}
So what's causing the child entities(Interests) to lose their datacontext when I do member.Subscribe() and how do I go about fixing this?
It seems there's some code missing here, but I'll take a stab anyway because I think I have an idea what's going on.
If you have a different DataContext created for your MembershipRepository and your SubscriberRepository you're going to have issues related to entities "having been loaded from another DataContext." (as the Exception you posted points out). You can't just take an object out of one DataContext and save it into another.
It seems that you might have an architectural issue here. Should these 2 repositories actually be separate? If so, should they have completely different DataContexts? I would probably recommend using Dependency Injection to inject your DataContexts into your Repositories. Then you can decide how to cache your DataContexts.
That line of code you commented out is being flagged by the DataContext as a new record, even though it's likely that the record already exists, due to the error message.
Change the line to:
newSubscriber.Interests.Add(DataContext.Interests.Where(a => a.Id == 1).Single());
Now, the DataContext will know that record is one that already exists, and won't try to add it as an Insert to the ChangeSet.
Found the solution to this myself. Turns out it was the ConvertInterests() method causing it. The converted interest object had an invalid declaration which compiled ok.
Thinking the code was simple enough, I didn't create a test for it. I should have known better!
I am having a really hard time attempting to debug LINQ to SQL and submitting changes.
I have been using http://weblogs.asp.net/scottgu/archive/2007/07/31/linq-to-sql-debug-visualizer.aspx, which works great for debugging simple queries.
I'm working in the DataContext Class for my project with the following snippet from my application:
JobMaster newJobToCreate = new JobMaster();
newJobToCreate.JobID = 9999
newJobToCreate.ProjectID = "New Project";
this.UpdateJobMaster(newJobToCreate);
this.SubmitChanges();
I will catch some very odd exceptions when I run this.SubmitChanges;
Index was outside the bounds of the array.
The stack trace goes places I cannot step into:
at System.Data.Linq.IdentityManager.StandardIdentityManager.MultiKeyManager`3.TryCreateKeyFromValues(Object[] values, MultiKey`2& k)
at System.Data.Linq.IdentityManager.StandardIdentityManager.IdentityCache`2.Find(Object[] keyValues)
at System.Data.Linq.IdentityManager.StandardIdentityManager.Find(MetaType type, Object[] keyValues)
at System.Data.Linq.CommonDataServices.GetCachedObject(MetaType type, Object[] keyValues)
at System.Data.Linq.ChangeProcessor.GetOtherItem(MetaAssociation assoc, Object instance)
at System.Data.Linq.ChangeProcessor.BuildEdgeMaps()
at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode)
at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode)
at System.Data.Linq.DataContext.SubmitChanges()
at JobTrakDataContext.CreateNewJob(NewJob job, String userName) in D:\JobTrakDataContext.cs:line 1119
Does anyone have any tools or techniques they use? Am I missing something simple?
EDIT:
I've setup .net debugging using Slace's suggestion, however the .net 3.5 code is not yet available: http://referencesource.microsoft.com/netframework.aspx
EDIT2:
I've changed to InsertOnSubmit as per sirrocco's suggestion, still getting the same error.
EDIT3:
I've implemented Sam's suggestions trying to log the SQL generated and to catch the ChangeExceptoinException. These suggestions do not shed any more light, I'm never actually getting to generate SQL when my exception is being thrown.
EDIT4:
I found an answer that works for me below. Its just a theory but it has fixed my current issue.
I always found useful to know exactly what changes are being sent to the DataContext in the SubmitChanges() method.
I use the DataContext.GetChangeSet() method, it returns a ChangeSet object instance that holds 3 read-only IList's of objects which have either been added, modified, or removed.
You can place a breakpoint just before the SubmitChanges method call, and add a Watch (or Quick Watch) containing:
ctx.GetChangeSet();
Where ctx is the current instance of your DataContext, and then you'll be able to track all the changes that will be effective on the SubmitChanges call.
First, thanks everyone for the help, I finally found it.
The solution was to drop the .dbml file from the project, add a blank .dbml file and repopulate it with the tables needed for my project from the 'Server Explorer'.
I noticed a couple of things while I was doing this:
There are a few tables in the system named with two words and a space in between the words, i.e. 'Job Master'. When I was pulling that table back into the .dbml file it would create a table called 'Job_Master', it would replace the space with an underscore.
In the orginal .dbml file one of my developers had gone through the .dbml file and removed all of the underscores, thus 'Job_Master' would become 'JobMaster' in the .dbml file. In code we could then refer to the table in a more, for us, standard naming convention.
My theory is that somewhere, the translation from 'JobMaster' to 'Job Master' while was lost while doing the projection, and I kept coming up with the array out of bounds error.
It is only a theory. If someone can better explain it I would love to have a concrete answer here.
My first debugging action would be to look at the generated SQL:
JobMaster newJobToCreate = new JobMaster();
newJobToCreate.JobID = 9999
newJobToCreate.ProjectID = "New Project";
this.UpdateJobMaster(newJobToCreate);
this.Log = Console.Out; // prints the SQL to the debug console
this.SubmitChanges();
The second would be to capture the ChangeConflictException and have a look at the details of failure.
catch (ChangeConflictException e)
{
Console.WriteLine("Optimistic concurrency error.");
Console.WriteLine(e.Message);
Console.ReadLine();
foreach (ObjectChangeConflict occ in db.ChangeConflicts)
{
MetaTable metatable = db.Mapping.GetTable(occ.Object.GetType());
Customer entityInConflict = (Customer)occ.Object;
Console.WriteLine("Table name: {0}", metatable.TableName);
Console.Write("Customer ID: ");
Console.WriteLine(entityInConflict.CustomerID);
foreach (MemberChangeConflict mcc in occ.MemberConflicts)
{
object currVal = mcc.CurrentValue;
object origVal = mcc.OriginalValue;
object databaseVal = mcc.DatabaseValue;
MemberInfo mi = mcc.Member;
Console.WriteLine("Member: {0}", mi.Name);
Console.WriteLine("current value: {0}", currVal);
Console.WriteLine("original value: {0}", origVal);
Console.WriteLine("database value: {0}", databaseVal);
}
}
}
You can create a partial class for your DataContext and use the Created or what have you partial method to setup the log to the console.out wrapped in an #if DEBUG.. this will help you to see the queries executed while debugging any instance of the datacontext you are using.
I have found this useful while debugging LINQ to SQL exceptions..
partial void OnCreated()
{
#if DEBUG
this.Log = Console.Out;
#endif
}
The error you are referring to above is usually caused by associations pointing in the wrong direction. This happens very easily when manually adding associations to the designer since the association arrows in the L2S designer point backwards when compared to data modelling tools.
It would be nice if they threw a more descriptive exception, and maybe they will in a future version. (Damien / Matt...?)
This is what I did
...
var builder = new StringBuilder();
try
{
context.Log = new StringWriter(builder);
context.MY_TABLE.InsertAllOnSubmit(someData);
context.SubmitChanges();
}
finally
{
Log.InfoFormat("Some meaningful message here... ={0}", builder);
}
A simple solution could be to run a trace on your database and inspect the queries run against it - filtered ofcourse to sort out other applications etc. accessing the database.
That ofcourse only helps once you get past the exceptions...
VS 2008 has the ability to debug though the .NET framework (http://blogs.msdn.com/sburke/archive/2008/01/16/configuring-visual-studio-to-debug-net-framework-source-code.aspx)
This is probably your best bet, you can see what's happening and what all the properties are at the exact point in time
Why do you do UpdateJobMaster on a new instance ? Shouldn't it be InsertOnSubmit ?
JobMaster newJobToCreate = new JobMaster();
newJobToCreate.JobID = 9999
newJobToCreate.ProjectID = "New Project";
this.InsertOnSubmit(newJobToCreate);
this.SubmitChanges();
This almost certainly won't be everyone's root cause, but I encountered this exact same exception in my project - and found that the root cause was that an exception was being thrown during construction of an entity class. Oddly, the true exception is "lost" and instead manifests as an ArgumentOutOfRange exception originating at the iterator of the Linq statement that retrieves the object/s.
If you are receiving this error and you have introduced OnCreated or OnLoaded methods on your POCOs, try stepping through those methods.
Hrm.
Taking a WAG (Wild Ass Guess), it looks to me like LINQ - SQL is trying to find an object with an id that doesn't exist, based somehow on the creation of the JobMaster class. Are there foreign keys related to that table such that LINQ to SQL would attempt to fetch an instance of a class, which may not exist? You seem to be setting the ProjectID of the new object to a string - do you really have an id that's a string? If you're trying to set it to a new project, you'll need to create a new project and get its id.
Lastly, what does UpdateJobMaster do? Could it be doing something such that the above would apply?
We have actually stopped using the Linq to SQL designer for our large projects and this problem is one of the main reasons. We also change a lot of the default values for names, data types and relationships and every once in a while the designer would lose those changes. I never did find an exact reason, and I can't reliably reproduce it.
That, along with the other limitations caused us to drop the designer and design the classes by hand. After we got used to the patterns, it is actually easier than using the designer.
I posted a similar question earlier today here: Strange LINQ Exception (Index out of bounds).
It's a different use case - where this bug happens during a SubmitChanges(), mine happens during a simple query, but it is also an Index out of range error.
Cross posting in this question in case the combination of data in the questions helps a good Samaritan answer either :)
Check that all the "primary key" columns in your dbml actually relate to the primary keys on the database tables. I just had a situation where the designer decided to put an extra PK column in the dbml, which meant LINQ to SQL couldn't find both sides of a foreign key when saving.
I recently encountered the same issue: what I did was
Proce proces = unit.Proces.Single(u => u.ProcesTypeId == (from pt in context.ProcesTypes
where pt.Name == "Fix-O"
select pt).Single().ProcesTypeId &&
u.UnitId == UnitId);
Instead of:
Proce proces = context.Proces.Single(u => u.ProcesTypeId == (from pt in context.ProcesTypes
where pt.Name == "Fix-O"
select pt).Single().ProcesTypeId &&
u.UnitId == UnitId);
Where context was obviously the DataContext object and "unit" an instance of Unit object, a Data Class from a dbml file.
Next, I used the "proce" object to set a property in an instance of another Data Class object. Probably the LINQ engine could not check whether the property I was setting from the "proce" object, was allowed in the INSERT command that was going to have to be created by LINQ to add the other Data Class object to the database.
I had the same non speaking error.
I had a foreign key relation to a column of a table that was not the primary key of the table, but a unique column.
When I changed the unique column to be the primary key of the table the problem went away.
Hope this helps anyone!
Posted my experiences with this exception in an answer to SO# 237415
I ended up on this question when trying to debug my LINQ ChangeConflictException. In the end I realized the problem was that I manually added a property to a table in my DBML file, but I forgot to set the properties like Nullable (should have been true in my case) and Server Data Type
Hope this helps someone.
This is a long time ago, but I had the same problem and the error was because of a trigger with a select statement. Something like
CREATE TRIGGER NAME ON TABLE1 AFTER UPDATE AS SELECT table1.key from table1
inner join inserted on table1.key = inserted.key
When linq-to-sql runs the update command, it also runs a select statement to receive the auto generated values in the same query and expecting the first record set to contains the columns "asked for" but in this case the first row was the columns from the select statement in the trigger. So linq-to-sql was expecting two autogenerated columns, but it only received one column (with wrong data) and that was causing this exception.