I am creating an instance of Unit of Work manually and use it to create new row. The problem is that even though my row is created successfully, the EntityId property in SaveResponse is null. (Error property is also null)
using (var conn = sqlConnStrings.NewByKey("Default"))
{
using (var uow = new UnitOfWork(conn))
{
resp = Create(uow, req);
// resp.EntityId is null despite successful insert to DB.
uow.Commit();
}
// accessing resp variable outside the using block doesn't help.
}
Related
I have the following logic:
try
{
using (var contents = new StreamReader(file.InputStream).ReadToEnd())
{
var rows = contents.Split(new[] { Environment.NewLine }, StringSplitOptions.None);
rows.ForEach(r => mids.Add(r.Split(',')[0]));
}
}
catch(IOException e)
{}
finally
{
contents = null;
}
In the using statement I have an error in the question. It happened probably because I use .ReadToEnd() method.
Without the using statement I would need to use try/catch/finally for a clean up (to fix veracode resource clean up issue)
How can I fix that, so I don't need to use try\catch\finally and use only the using statement?
So, using should be used with object which implements IDisposable interface. You calling ReadToEnd method which returns string and contents is not a IDisposable (because string is not).
You should use it like this:
using (var streamReader = new StreamReader(file.InputStream))
{
var contents = streamReader.ReadToEnd();
// Some actions
}
You want to clean up StreamReader, contents will be collected by GC when method will finished because it has type string.
i have a database containing Song objects. The song class has > 30 properties.
My Music Tagging application is doing changes on a song on the file system.
It then does a lookup in the database using the filename.
Now i have a Song object, which i created in my Tagging application by reading the physical file and i have a Song object, which i have just retrieved from the database and which i want to update.
I thought i just could grab the ID from the database object, replace the database object with my local song object, set the saved id and store it.
But Raven claims that i am replacing the object with a different object.
Do i really need to copy every single property over, like this?
dbSong.Artist = songfromFilesystem.Artist;
dbSong.Album = songfromFileSystem.Album;
Or are there other possibilities.
thanks,
Helmut
Edit:
I was a bit too positive. The suggestion below works only in a test program.
When doing it in my original code i get following exception:
Attempted to associate a different object with id 'TrackDatas/3452'
This is produced by following code:
try
{
originalFileName = Util.EscapeDatabaseQuery(originalFileName);
// Lookup the track in the database
var dbTracks = _session.Advanced.DocumentQuery<TrackData, DefaultSearchIndex>().WhereEquals("Query", originalFileName).ToList();
if (dbTracks.Count > 0)
{
track.Id = dbTracks[0].Id;
_session.Store(track);
_session.SaveChanges();
}
}
catch (Exception ex)
{
log.Error("UpdateTrack: Error updating track in database {0}: {1}", ex.Message, ex.InnerException);
}
I am first looking up a song in the database and get a TrackData object in dbTracks.
The track object is also of type TrackData and i just put the ID from the object just retrieved and try to store it, which gives the above error.
I would think that the above message tells me that the objects are of different types, which they aren't.
The same error happens, if i use AutoMapper.
any idea?
You can do what you're trying: replace an existing object using just the ID. If it's not working, you might be doing something else wrong. (In which case, please show us your code.)
When it comes to updating existing objects in Raven, there are a few options:
Option 1: Just save the object using the same ID as an existing object:
var song = ... // load it from the file system or whatever
song.Id = "Songs/5"; // Set it to an existing song ID
DbSession.Store(song); // Overwrites the existing song
Option 2: Manually update the properties of the existing object.
var song = ...;
var existingSong = DbSession.Load<Song>("Songs/5");
existingSong.Artist = song.Artist;
existingSong.Album = song.Album;
Option 3: Dynamically update the existing object:
var song = ...;
var existingSong = DbSession.Load<Song>("Songs/5");
existingSong.CopyFrom(song);
Where you've got some code like this:
// Inside Song.cs
public virtual void CopyFrom(Song other)
{
var props = typeof(Song)
.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance)
.Where(p => p.CanWrite);
foreach (var prop in props)
{
var source = prop.GetValue(other);
prop.SetValue(this, source);
}
}
If you find yourself having to do this often, use a library like AutoMapper.
Automapper can automatically copy one object to another with a single line of code.
Now that you've posted some code, I see 2 things:
First, is there a reason you're using the Advanced.DocumentQuery syntax?
// This is advanced query syntax. Is there a reason you're using it?
var dbTracks = _session.Advanced.DocumentQuery<TrackData, DefaultSearchIndex>().WhereEquals("Query", originalFileName).ToList();
Here's how I'd write your code using standard LINQ syntax:
var escapedFileName = Util.EscapeDatabaseQuery(originalFileName);
// Find the ID of the existing track in the database.
var existingTrackId = _session.Query<TrackData, DefaultSearchIndex>()
.Where(t => t.Query == escapedFileName)
.Select(t => t.Id);
if (existingTrackId != null)
{
track.Id = existingTrackId;
_session.Store(track);
_session.SaveChanges();
}
Finally, #2: what is track? Was it loaded via session.Load or session.Query? If so, that's not going to work, and it's causing your problem. If track is loaded from the database, you'll need to create a new object and save that:
var escapedFileName = Util.EscapeDatabaseQuery(originalFileName);
// Find the ID of the existing track in the database.
var existingTrackId = _session.Query<TrackData, DefaultSearchIndex>()
.Where(t => t.Query == escapedFileName)
.Select(t => t.Id);
if (existingTrackId != null)
{
var newTrack = new Track(...);
newTrack.Id = existingTrackId;
_session.Store(newTrack);
_session.SaveChanges();
}
This means you already have a different object in the session with the same id. The fix for me was to use a new session.
I am trying to find the perfect way to handle this exception and force client changes to overwrite any other changes that caused the conflict. The approach that I came up with is to wrap the call to Session.Transaction.Commit() in a loop, inside the loop I would do a try-catch block and handle each stale object individually by copying its properties, except row-version property then refreshing the object to get latest DB data then recopying original values to the refreshed object and then doing a merge. Once I loop I will commit and if any other StaleObjectStateException take place then the same applies. The loop keeps looping until all conflicts are resolved.
This method is part of a UnitOfWork class. To make it clearer I'll post my code:
// 'Client-wins' rules, any conflicts found will always cause client changes to
// overwrite anything else.
public void CommitAndRefresh() {
bool saveFailed;
do {
try {
_session.Transaction.Commit();
_session.BeginTransaction();
saveFailed = false;
} catch (StaleObjectStateException ex) {
saveFailed = true;
// Get the staled object with client changes
var staleObject = _session.Get(ex.EntityName, ex.Identifier);
// Extract the row-version property name
IClassMetadata meta = _sessionFactory.GetClassMetadata(ex.EntityName);
string rowVersionPropertyName = meta.PropertyNames[meta.VersionProperty] as string;
// Store all property values from client changes
var propertyValues = new Dictionary<string, object>();
var publicProperties = staleObject.GetType().GetProperties();
foreach (var p in publicProperties) {
if (p.Name != rowVersionPropertyName) {
propertyValues.Add(p.Name, p.GetValue(staleObject, null));
}
}
// Get latest data for staled object from the database
_session.Refresh(staleObject);
// Update the data with the original client changes except for row-version
foreach (var p in publicProperties) {
if (p.Name != rowVersionPropertyName) {
p.SetValue(staleObject, propertyValues[p.Name], null);
}
}
// Merge
_session.Merge(staleObject);
}
} while (saveFailed);
}
The above code works fine and handle concurrency with the client-wins rule. However, I was wondering if there is any built-in capabilities in NHibernate to do this for me or if there is a better way to handle this.
Thanks in advance,
What you're describing is a lack of concurrency checking. If you don't use a concurrency strategy (optimistic-lock, version or pessimistic), StaleStateObjectException will not be thrown and the update will be issued.
Okay, now I understand your use case. One important point is that the ISession should be discarded after an exception is thrown. You can use ISession.Merge to merge changes between a detached a persistent object rather than doing it yourself. Unfortunately, Merge does not cascade to child objects so you still need to walk the object graph yourself. So the implementation would look something like:
catch (StaleObjectStateException ex)
{
if (isPowerUser)
{
var newSession = GetSession();
// Merge will automatically get first
newSession.Merge(staleObject);
newSession.Flush();
}
}
The following method queries my database, using a new session. If the query succeeds, it attaches (via "Lock") the result to a "MainSession" that is used to support lazy loading from a databound WinForms grid control.
If the result is already in the MainSession, I get the exception:
NHibernate.NonUniqueObjectException : a different object with the same identifier value was already associated with the session: 1, of entity: BI_OverlordDlsAppCore.OfeDlsMeasurement
when I attempt to re-attach, using the Lock method.
This happens even though I evict the result from the MainSession before I attempt to re-attach it.
I've used the same approach when I update a result, and it works fine.
Can anyone explain why this is happening?
How should I go about debugging this problem?
public static OfeMeasurementBase GetExistingMeasurement(OverlordAppType appType, DateTime startDateTime, short runNumber, short revision)
{
OfeMeasurementBase measurement;
var mainSession = GetMainSession();
using (var session = _sessionFactory.OpenSession())
using (var transaction = session.BeginTransaction())
{
// Get measurement that matches params
measurement =
session.CreateCriteria(typeof(OfeMeasurementBase))
.Add(Expression.Eq("AppType", appType))
.Add(Expression.Eq("StartDateTime", startDateTime))
.Add(Expression.Eq("RunNumber", runNumber))
.Add(Expression.Eq("Revision", revision))
.UniqueResult() as OfeMeasurementBase;
// Need to evict from main session, to prevent potential
// NonUniqueObjectException if it's already in the main session
mainSession.Evict(measurement);
// Can't be attached to two sessions at once
session.Evict(measurement);
// Re-attach to main session
// Still throws NonUniqueObjectException!!!
mainSession.Lock(measurement, LockMode.None);
transaction.Commit();
}
return measurement;
}
I resolved the problem after finding this Ayende post on Cross Session Operations.
The solution was to use ISession.Merge to get the detached measurement updated in the main session:
public static OfeMeasurementBase GetExistingMeasurement(OverlordAppType appType, DateTime startDateTime, short runNumber, short revision)
{
OfeMeasurementBase measurement;
var mainSession = GetMainSession();
using (var session = _sessionFactory.OpenSession())
using (var transaction = session.BeginTransaction())
{
// Get measurement that matches params
measurement =
session.CreateCriteria(typeof(OfeMeasurementBase))
.Add(Expression.Eq("AppType", appType))
.Add(Expression.Eq("StartDateTime", startDateTime))
.Add(Expression.Eq("RunNumber", runNumber))
.Add(Expression.Eq("Revision", revision))
.UniqueResult() as OfeMeasurementBase;
transaction.Commit();
if (measurement == null) return null;
// Merge back into main session, in case it has changed since main session was
// originally loaded
var mergedMeasurement = (OfeMeasurementBase)mainSession.Merge(measurement);
return mergedMeasurement;
}
}
I am using ASP.NET MVC2 in Visual Studio 2008. I believe the SQL Server is 2005. I am using Entity Framework to access the database.
I've got the following table with a composite primary key based upon iRequest and sCode:
RequestbyCount
iRequest integer
sCode varchar(10)
iCount integer
iRequest is a foreign key to a list of requests.
When a request is updated, I want to clear out the existing RequestbyCounts for that request and then add in the new RequestbyCounts. More than likely, the only difference between the old rows will be the Count.
For my code, I attempt it as follows:
//delete ALL our old requests
var oldEquipList = (from eq in myDB.dbEquipmentRequestedbyCountSet
where eq.iRequestID == oldData.iRequestID
select eq).ToList();
foreach (var oldEquip in oldEquipList)
{
myDB.DeleteObject(oldEquip);
}
// myDB.SaveChanges(); <---- adding this line makes it work
//add in our new requests
foreach (var equip in newData.RequestList) //newData.RequestList is a List object
{
if (equip.iCount > 0)
{
//add in our actual request items
RequestbyCount reqEquip = new RequestbyCount();
reqEquip.sCodePrefix = equip.sCodePrefix;
reqEquip.UserRequest = newRequest;
reqEquip.iCount = equip.iCount;
myDB.AddToRequestbyCount(reqEquip);
}
}
myDB.SaveChanges(); //save our results
The issue is when I run it with the intermediate SaveChanges line uncommented, it works as desired. But my understanding is that doing this breaks the transaction apart.
If I leave the intermediate SaveChanges commented out as above, the process fails and I receive a
Violation of PRIMARY KEY constraint
'PK_RequestbyCount'. Cannot insert
duplicate key in object
'dbo.RequestbyCount'.\r\nThe statement
has been terminated.
Obviously, without doing the intermediate SaveChanges, the old rows are NOT removed as desired.
I do NOT want the results saved unless everything succeeds.
I would rather not take the following approach:
//add in our new requests
foreach (var equip in newData.RequestList)
{
if (equip.iCount > 0) && (**it isn't in the database**)
{
//add in our actual request items
RequestbyCount reqEquip = new RequestbyCount();
reqEquip.sCodePrefix = equip.sCodePrefix;
reqEquip.UserRequest = newRequest;
reqEquip.iCount = equip.iCount;
myDB.AddToRequestbyCount(reqEquip);
} else if (**it is in the database**) && (equip.iCount == 0) {
**remove from database**
} else {
**edit the value in the database**
}
}
Am I stuck doing the above code that basically makes a bunch of little calls to the database to check if an item exists?
Or is there some method that tell the framework to attempt to delete the rows I want but rollback if there is a failure inserting the new rows?
You don't appear to be using transactions at all. You need to wrap all your code in
using (TransactionScope transaction = new TransactionScope())
{
...
transaction.Complete();
}
Even better
using (TransactionScope transaction = new TransactionScope())
{
try
{
your code
transaction.Complete();
}
catch(Exception)
{
// handle error
}
}
Using the try/catch block will ensure that the transaction is not committed if an exception occurs, which is what you stated you wanted.
Lot's more on entity framework transactions at Microsoft's web site. The explanations there are quite good.