Error Message: "Store update, insert, or delete statement affected an unexpected number of rows (0). Entities may have been modified or deleted since entities were loaded. Refresh ObjectStateManager entries."
Hello All,
I've created a Code First TPH(Table Per Hierarchy) within MVC and EF with a SQL compact db.
Here's the Class diagram/Hierarchy:
Class Diagram
Client and SalesRep both inherit the BaseUser class. The Key is "UserID" and it's coded with the Data Annotation [Key](I'm aware that 'ID' should set it as well)
Here's where I'm at: I can seed the database with a few entries. When I try to set the "UserID" in the seeding method it seems to ignore it and just apply the UserID in numerical order...(Seems ok to me?)
furthermore here's my DbContext
public class SiteDB:DbContext
{
public DbSet<BaseUser> AllUsers { get; set; }//enable TPH
public DbSet<SalesRep> SalesReps { get; set; }
public DbSet<Client> Clients { get; set; }
}
Next,
I have created a controller for Clients -> ClientsController with strongly typed Razor Views. With this. I now have a CRUD for the Clients. I can create new Clients without any issue, but when I try to edit a Client entry, I get the error message stated above.
I did notice something interesting I stepped through the code and the error is happening on the db.SaveChanges();
When the client is passed back into the ActionResult Edit method the UserID=0! Bizarre? I'm not sure if this is a bug or if it's an actual issue that's causing this.
UserID=0
Your help with this is appreciated. Thanks!
To modify an entity you need to get it from the database: when you pass back the modified values in the Edit action you need to retrive the entity from the db object, getting it by ID, apply the modified values and save it.
Here an example:
public ActionResult Edit(int id, MyModel model){
using (SiteDBdb = new SiteDB()){
Client cl = (from c in db.Clients where c.id == id select c).First();
cl.MyProp = model.MyProp;
...
db.SaveChanges();
}
...
}
Related
I'm working with Fluent nHibernate on a legacy database and have a main Person table and several extension tables containing additional information about the person. These extension tables are one-to-one, meaning that a person will only have one row on the extension table and the extension table should always map back to one person.
Table: Person
Columns: PersonID, FirstName, LastName, etc.
Table: PersonLogin
Columns: PersonID (FK, unique), UserName, Password, etc.
I have my mappings defined as this (with the irrelevant properties omitted):
public PersonMap()
{
Table("Person");
Id(x => x.Id, "PersonID").Not.Nullable();
References(x => x.Login, "PersonID").LazyLoad();
}
public LoginMap()
{
Table("PersonLogin");
Id(x => x.Id, "PersonID").GeneratedBy.Foreign("Person");
References(x => x.Person, "PersonID").LazyLoad();
}
This works when I have data on both tables, but I recently learned that some of the extension tables don't have data for all Person rows. This caused me to get errors during the query. So, I added .NotFound.Ignore() to my PersonMap making it look like this:
References(x => x.Login, "PersonID").LazyLoad().NotFound.Ignore();
That caused me to get unnecessary selects from the Login table due to https://nhibernate.jira.com/browse/NH-1001 when my business layer doesn't need to project any of the extension table values. It is causing the performance to be terrible in some of my search queries.
I've scoured a lot of posts, but haven't found a rock solid answer about how to address this scenario. Below are the options I've tried:
Option One:
Create rows on the extension table to ensure there is no Person without a row on the extension table and then remove the .NotFound.Ignore().
The issue with this option is that it's a legacy database and I'm not sure where I'd need to update to ensure that a PersonLogin is inserted when a Person is inserted.
Option Two:
Remove the PersonLogin reference from my PersonMap and custom load it inside my Person class. Like this:
public class Person
{
/// <summary> Gets or sets the PersonID </summary>
public virtual int Id { get; set; }
private bool loadedLogin;
private PersonLogin login;
public virtual PersonLogin Login
{
get
{
if (!loadedLogin)
{
login = SessionManager.Session().Get<PersonLogin>(Id);
loadedLogin = true;
}
return login;
}
set
{
login = value;
loadedLogin = true;
}
}
}
The issue I'm having with it is that I can't eagerly fetch the data when performing a query to pull back a large number of Person objects and their Logins.
Option Three:
I just started playing to see if I could write a custom IEntityNotFoundDelegate to not throw the exception for these objects.
private class CustomEntityNotFoundDelegate : IEntityNotFoundDelegate
{
public void HandleEntityNotFound(string entityName, object id)
{
if (entityName == "my.namespace.PersonLogin")
{
return;
}
else
{
throw new ObjectNotFoundException(id, entityName);
}
}
}
And I added this to the config
cfg.EntityNotFoundDelegate = new CustomEntityNotFoundDelegate();
It catches my scenario and returns back now instead of throwing the error, but now when I try to project those PersonLogin properties onto my business objects, it's attempting to use the Proxy object and throws this error that I'm trying to figure out if I can handle cleanly (possibly in a IPostLoadEventListener).
System.Reflection.TargetException occurred
Message = Non-static method requires a target
I think I've got this working now by keeping the .NotFound.Ignore().
I originally stated:
That caused me to get unnecessary selects from the Login table due to https://nhibernate.jira.com/browse/NH-1001 when my business layer doesn't need to project any of the extension table values. It is causing the performance to be terrible in some of my search queries.
I was able to tweak my LINQ queries to use the IQueryOver in some instances and to improve my use of LINQ in other scenarios to project only the necessary values. This appears to have resolved the queries from pulling back the extension tables since their values were not needed in the projections.
I thought that my queries weren't projecting these extension tables, but figured out that I had a method ToKeyValuePair that I was using in the projection to concatenate the ID and a Name field together of some related properties. That method was causing the objects to load completely since LINQ wasn't able to determine that the needed fields were present without joining to the extension table.
I am trying to implement a custom task scheduler system.
I have a following (simplified) entity model:
class User
{
public virtual long UserId { get; set; }
public virtual string Name { get; set; }
}
class Task
{
public virtual long TaskId { get; set; }
public virtual long? UserId { get; set; }
public virtual string TaskName { get; set; }
public virtual Guid SchedulerSessionUid { get; set; }
}
For now, corresponding SQL tables are straight forward with fields mapping exactly as they appear in the classes above.
The scheduler is a C# Windows console app. It will run once per day.
It should work in a following way (simplified):
generate a Guid for current session
try selecting next User entity, which does not already have a task scheduled in the current scheduler session (Guid compare); if no such a User found, go to the step 5.
add a new Task for the user selected in the step 2.
go to step 2.
exit the application
It seems a pretty trivial problem, but I have a problem implementing the second step. I have tried various queries, but there are some rules which always stop me.
Here are some rules which I have to obey while implementing the step 1:
I am not allowed to modify the User class or User SQL table
I may modify Task class and table, if it will help to solve the problem
I may add a new table or a stored procedure, if it will help
I have to implement it in a way which is as compatible with NHibernate and LINQ as possible
there might exist also some tasks which are not associated with any User object (the scheduler will ignore those, but still I have to keep that in mind while designing the SQL/LINQ query and NHibernate mapping).
Here are some real world example how it should work.
Users
-----------------
UserId Name
-----------------
1 First
2 Second
Tasks
--------------------------------------------------------
TaskId UserId SchedulerSessionUid
--------------------------------------------------------
1 NULL 6d8e48d0-4e92-477e-82fa-cd957e7dc201
2 1 d213cfc8-23d6-49fb-b4e3-9ff3b60af6c4
3 1 9ee042df-88a7-447e-adbd-e7551ed50ae5
1.Now when the Scheduler runs, it generates a current session id = 76ea57fa-8c89-4c05-9ca2-a450b1f8a032.
Now it should issue the magical LINQ query to NHibernate LINQ
provider to get a User entity
In the first iteration the query should return the User entity with
UserId=1 because there are no tasks in the current session for that
User yet
Now the Scheduler creates a new task with UserId=1,
SchedulerSessionUid=76ea57fa-8c89-4c05-9ca2-a450b1f8a032.
In the next iteration the Scheduler should get a User with UserId=2. Again, a new task is inserted with UserId=2, SchedulerSessionUid=76ea57fa-8c89-4c05-9ca2-a450b1f8a03.
In the next iteration the Scheduler should get no users, so it exits.
What LINQ query could I use to get the User for the step 2? What changes in my SQL schema and entity model do I need?
If I now follow you correctly, you need to get a (just one) user for which there are no tasks with the given session id. Am I correct?
Users.Where(u => !Tasks.Any(t = > t.UserId == u.UserId && t.SchedulerSessionUid == curSession)).FirstOrDefault()
Edit:
Since you're doing several spins through this, would you perhaps be faster doing:
foreach(var user toDealWith Users.Where(u => !Tasks.Any(t = > t.UserId == u.UserId && t.SchedulerSessionUid == curSession)))
{
//do stuff
}
Rather than keep hitting the database each time?
I started using NHibernate today, but I cannot figure out how I setup a simple relation between two tables. I don't really know what it's called, it could be one-to-many or foreign key relation (I'm not that into database design and the terms used), but here's a very simple example.
I have a table Product with attributes Id (PK), ProductName and CategoryId. Then I have a table Categories with attributes Id (PK) and CategoryName.
I created these classes:
public class Product
{
public virtual int Id { get; set; }
public virtual string ProductName { get; set; }
public virtual int CategoryId { get; set; }
public virtual Category Category { get; set; }
public virtual string CategoryName
{
get { return this.Category == null ? String.Empty : this.Category.CategoryName; }
}
}
public class Category
{
public virtual int Id { get; set; }
public virtual string CategoryName { get; set; }
}
In other words, I simply want the Product to store to which category it belongs (via the CategoryId attribute which points to an Id in the Categories table). I don't need the Category class to hold a list of related Products, if that makes it any simpler.
To make it even more clear what I'm after, this is the SQL that I'm expecting:
SELECT Products.*, Categories.*
FROM Products INNER JOIN Categories ON Products.CategoryId = Categories.Id
at least that's what I think it should be (again, I'm not that good at database design or queries).
I can't figure out which kind of mapping I need for this. I suppose I need to map it in the Product.hbm.xml file. But do I map the CategoryId as well? And how do I map the Category property?
It seems like I would need a 'one-to-many' relation since I have ONE category per product (or is this reasoning backward?) but it seems like there is no one-to-many mapping...
Thanks for any help!
Addition:
I tried to add the many-to-one relation in the Person mapping, but I keep getting an exception saying "Creating proxy failed", and in the inner exception "Ambiguous match found".
I should maybe mention I am using an old version of NHibernate (1.2 I think) because that is the only one I got running with MS Access due to it not finding the JetDriver in newer versions.
I've put the mapping files, classes, and code where the error occurs in screenshots because I can't figure out how to post XML code here... It keeps reading it as html tags and skipping half of it. Anyway.
The mappings:
http://www.nickthissen.nl/Images/tmp7B5A.png
The classes:
http://www.nickthissen.nl/Images/tmpF809.png
The loading code where the error occurs:
http://www.nickthissen.nl/Images/tmp46B6.png
(As I said, the inner exception says "Ambiguous match found".
(Product in my example has been replaced by Person)
The Person and Category classes inherit Entity which is an abstract base class and defines the Id, Deleted, CreatedTime and UpdatedTime properties.
The code where the error occurs is in a generic 'manager' class (type parameter TEntity which must inherit Entity). It is simply supposed to load all entities with the Deleted attribute false. In this case, TEntity is 'Person'.
It works fine if I leave out the many-to-one Category mapping in the Person mapping, but then obviously the Category property is always null.
Oh yeah, sorry about the mix between C# and VB, the C# code is in a generic framework I use for multiple projects while the VB part is the actual implementation of that framework on my website and I just happened to use VB for that.
Help? Thanks!
In your Product class only needs to contain a Category object, you don't need a CategoryId property. Then in your Product mapping you need to have this entry
<many-to-one name="Category" column="CategoryId" />
UPDATE:
Your mappings appear to be missing the fully qualified name of the mapped class in the tag. See http://nhibernate.info/doc/nh/en/index.html#mapping-declaration-class
UPDATE 2:
See if this helps you NHibernate 1.2 in a .NET 4.0 solution
The 'Ambiguous match found' exception was caused by the project targeting .NET Framework 4, which does not seem to be compatible with NHibernate 1.2.1. I switched to 3.5 and that seems to solve that particular issue.
Now on to the next. As you can see, the Person class has a CategoryName property that should return the name of the current Category object, or an empty string if the category happens to be null. This is so I can databind a collection of Person objects to a grid, specifying 'CategoryName' as a property to bind a column to.
Apparently this does not work with NHibernate. Whenever I try to databind my collection of persons, I get this exception:
"Property accessor 'CategoryName' on object 'NHibernateWebTest.Database.Person' threw the following exception:'Could not initialize proxy - the owning Session was closed.'"
This occurs on the 'DataBind' method call in this code:
public virtual void LoadGrid()
{
if (this.Grid == null) return;
this.Grid.DataSource = this.Manager.Load();
this.Grid.DataBind();
}
(This is an ASP.NET project and 'Grid' is a GridView)
'this.Manager' returns an existing instance of NHibernateEntityManager, and I've already shown its Load method before, it contains this:
public virtual EntityCollection Load()
{
using (ISession session = this.GetSession())
{
var entities = session
.CreateCriteria(typeof (TEntity))
.Add(Expression.Eq("Deleted", false))
.List();
return new EntityCollection(entities);
}
}
(THere's some generic type parameters in there but this website seems to hide them (due to the html like tags I guess)... Sorry about that).
This may have something to do with NHibernate itself, as I said I'm completely new to this. When I call my Load method I would expect it to return an EntityCollection(Of Person) with all its properties already set. It seems I have to keep the ISession open while I am databinding for some reason..? That seems a little strange...
Can I get around this? Can I make my Load method simply return a collection of persons already fully loaded, so that I can access CategoryName whenever I want?
Wait... Is this lazy loading perhaps?
I am working on an NHibernate project and have a question regarding updating transient entities.
Basically the workflow is as follows:
Create a DTO (projection) and send over the wire to client. This has a small subset of properties from the entity.
Client sends back the changed DTO
Map the DTO properties back onto the appropriate enitity so an UPDATE statement can be generated and executed by NH.
Save the entity
Point 4 is where I have the issue. Currently I can achieve this update using the session.Merge() method, however it must first load the entity from the db (assume no 2LC) before updating. So, both a select and an update statement are fired.
What I would like to do is create a transient instance of the entity, map the new values from the DTO, then have NH generate a SQL statement using only the properties I have changed. The additional select should be unnecessary as I already have the entity ID and the values required for the SET clause. Is this possible in NH?
Currently using session.Update(), all properties will be included in the update statement and an exception is raised due to the uninitialized properties that are not part of the DTO.
Essentially I need a way to specify which entity properties are dirty so only these are included in the update.
== EDIT ==
For example...
public class Person
{
public virtual int PersonId { get; set; }
public virtual string Firstname { get; set; }
public virtual string Nickname { get; set; }
public virtual string Surname { get; set; }
public virtual DateTime BirthDate { get; set; }
}
And the test case.
// Create the transient entity
Person p = new Person()
p.id = 1;
using (ISession session = factory.OpenSession())
{
session.Update(p);
// Update the entity – now attached to session
p.Firstname = “Bob”;
session.Flush();
}
I was hoping to generate a SQL statement similar to ‘UPDATE Persons SET Firstname = ‘Bob’ WHERE PersonID = 1’. Instead I get a DateTime out of range exception due to BirthDate not being initialised. It shouldn’t need BirthDate as it is not required for the SQL statement. Maybe this isn’t possible?
== /EDIT ==
Thanks in advance,
John
Dynamic-update is what you're looking for. In your mapping file (hbm.xml):
<class name="Foo" dynamic-update="true">
<!-- remainder of your class map -->
Be aware of the potential problems that this may cause. Let's say you have some domain logic that says either FirstName or Nickname must not be null. (Completely making this up.) Two people update Jon "Jonboy" Jonson at the same time. One removes his FirstName. Because dynamic-update is true, the update statement just nulls out Jon and the record is now "Jonboy" Jonson. The other simultaneous update removes his Nickname. The intent is Jon Jonboy. But only the null-out of the Nickname gets sent to the database. You now have a record with no FirstName or Nickname. If dynamic-update had been false, the second update would have set it to Jon Jonboy. Maybe this isn't an issue in your situation, but setting dynamic-update="true" has consequences and you should think through the implications.
UPDATE: Thanks for the code. That helped. The basic problem is NHibernate not having enough information. When you say session.Update(p), NHibernate has to associated a disconnected entity with the current session. It has a non-default PK. So NHibernate knows that it's an update and not an insert. When you say session.Update(p), NHibernate sees the whole entity as dirty and sends it to the database. (If you use session.Merge(obj), NHibernate selects the entity from the database and merges obj with it.) This is not what you really mean. You want to associate your object with the current session, but mark it as clean. The API is somewhat non-intuitive. You use session.Lock(obj, LockMode.None) as below.
using(var session = sessionFactory.OpenSession())
using(var tx = session.BeginTransaction()) {
var p = new Person {PersonId = 1};
session.Lock(p, LockMode.None); // <-- This is the secret sauce!
p.Firstname = "Bob";
// No need to call session.Update(p) since p is already associated with the session.
tx.Commit();
}
(N.B. dynamic-update="true" is specified in my mapping.)
This results in the following SQL:
UPDATE Person
SET Firstname = 'Bob' /* #p0_0 */
WHERE PersonId = 1 /* #p1_0 */
I need to write a row to the database regardless of whether it already exists or not. Before using NHibernate this was done with a stored procedure. The procedure would attempt an update and if no rows were modified it would fallback to an insert. This worked well because the application doesn't care if the record exists.
With NHibernate, the solutions I have found require loading the entity and modifying it, or deleting the entity so the new one can be inserted. The application does have to care if the record already exists. Is there a way around that?
Does the Id Matter?
Assigned Id
The object has a keyword as an assigned id and is the primary key in the table.
I understand that SaveOrUpdate() will call the Save() or Update() method as appropriate based on the Id. Using an assigned id, this won't work because the id isn't an unsaved-value. However a Version or Timestamp field could be used as an indicator instead. In reality, this isn't relevant because this only reflects on whether the object in memory has been associated with a record in the database; it does not indicate if the record exists or not in the database.
Generated Id
If the assigned id were truly the cause of the problem, I could use a generated id instead of the keyword as the primary key. This would avoid the NHibernate Insert/Update issue as it would effectively always insert. However, I still need to prevent duplicate keywords. With a unique index on the keyword column it will still throw an exception for a duplicate keyword even if the primary key is different.
Another Approach?
Perhaps the problem isn't really with NHibernate, but the way this is modeled. Unlike other areas of the application, this is more data-centric rather object-centric. It is nice that NHibernate makes it easy to read/write and eliminates the stored procedures. But the desire to simply write without regard to existing values doesn't fit well with the model of an object's identity model. Is there a better way to approach this?
I`m using
public IList<T> GetByExample<T>(T exampleInstance)
{
return _session.CreateCriteria(typeof(T))
.Add(Example.Create(exampleInstance))
.List<T>();
}
public void InsertOrUpdate<T>(T target)
{
ITransaction transaction = _session.BeginTransaction();
try
{
var res=GetByExample<T>(target);
if( res!=null && res.Count>0 )
_session.SaveOrUpdate(target);
else
_session.Save(target);
transaction.Commit();
}
catch (Exception)
{
transaction.Rollback();
throw;
}
finally
{
transaction.Dispose();
}
}
but FindByExample method returns all objects alike not objects with the exact ID what do you suggest ? since I have only object as parameter I don't have access to its specific ID field so I cannot use session.get(Object.class(), id);
Typically, NHibernate can rely on the unsaved-value to determine whether it should insert or create the entity. However, since you are assigning the ID, to NHibernate it looks like your entity has already been persisted. Therefore, you need to rely on versioning your object to let NHibernate know that it is a new object. See the following link for how to version your entity:
http://web.archive.org/web/20090831032934/http://devlicio.us/blogs/mike_nichols/archive/2008/07/29/when-flushing-goes-bad-assigned-ids-in-nhibernate.aspx
Use the session.SaveOrUpdate(object) method.
You can do
Obj j = session.get(Object.class(), id);
if (j != null)
session.merge(myObj);
else
session.saveOrUpdate(myObj);
Query objects where keyword = x, take FirstOrDefault. If it's null, Add new object, if it exists, update object that you got and call saveOrUpdate on it.
This worked for me:
Implementation
public void InsertOrUpdate<TEntity, TId>(TEntity entity) where TEntity : IIdentificableNh<TId>
{
var anyy = session.Get<TEntity>(entity.Id);
if (anyy != null)
{
session.Evict(anyy); //dispatch all data loaded, to allow updating 'entity' object.
session.Update(entity);
}
else
{
session.Save(entity);
}
session.Flush();
}
Entity
public class Caracteristica : IIdentificableNh<int>
{
public virtual int Id { get; set; }
public virtual string Descripcion { get; set; }
}
I had to create an interface (IIdentificableNh) that allows me to access the Id property value.
Usage example:
session.InsertOrUpdate<Caracteristica, int>(new Caracteristica { Id = 2, Descripcion = "Caracteristica2" });
call hibernate.saveOrUpdate() which will check if the object is in the database, update it if it is, and save (i.e. insert) it if it is not.