I have a mapping in FluentNHibernate for a HasMany relationship and I'd like to specify a Table on it to override the default Table that nHibernate will look in to find those objects that I have many of. Does that make sense?
So lets say I have a table for Invoices and a table for InvoiceItems and lets say I have table called InvoiceItemsTwo.
I have a class for Invoice and a Class for InvoiceItems as well, and their mappings are pretty straight forward. I'd like to specify in my mapping for Invoice, that it should look for it's items in InvoiceItemsTwo instead of the default InvoiceItems.
So my mapping of that relationship looks like this
HasMany(c => c.InvoiceItems).Cascade.SaveUpdate().Table("InvoiceItemsTwo");
But this doesn't work. I keep getting an error from my website at runtime that says Invalid object name 'InvoiceItems'.
Why is it ignoring the fact that I am explicitly specifying the Table in my mapping on the relationship?
I tried dumping the mapping at run time and it's being setup something like this
<bag cascade="save-update" table="InvoiceItemsTwo">
Any ideas?
The table attribute applies only to many-to-many relationships, not one-to-many.
you can't specify a different table in your mapping class. Fluent NHibernate uses the class mapped on the property list (InvoiceItems).
If yoy want to use another class to map your details table you must create a InvoceItemsTwo class and map it in your master table class.
You could map the list as composite-element instead of a one-to-many relation and then map it to another table. But it is not a good idea. Consider that NH needs to know where to store an object which is in memory. So it may happen that the object is stored in the wrong table.
Either store all the InvoiceItems in separate tables using composite-element instead of one-to-many and components instead of many-to-one (however this is called in Fluent).
Or store all the InvoiceItems in the same table and use regular references.
Related
Currently I have a table "ComponentAnalysis" and a table "HistoryOfUse" that I am trying to map in Fluent NHibernate.
A component analysis should only have 1 history of use and a history of use should belong to 1 component analysis. This would suggest to me that the tables should be set up for a 1 to 1 mapping. But the designer of the DB didn't set it up that way.
Instead "HistoryOfUse" has a column "ComponentAnalysisID" to specify what component analysis it belongs to. To conform to the database I should have HistoryOfUse References ComponentAnalysis and ComponentAnalysis should HasMany HistoryOfUse.
But if I do this then I need to have a list of type HistoryOfUse which seems fairly annoying. Is there a way to set this up, without changing the database, to allow ComponentAnalysis to have a single HistoryOfUse object even though, according to the DB structure, it should have a list of them?
You can use HasOne method to map your classes. Here is the detailed article about this.
Your class ComponentAnalysis will "HasOne(x => x.HistoryOfUse)". Column HistoryOfUse.ComponentAnalysisID should be a unique key and a foreign key referenced to the ComponentAnalysis.ID column.
It's been asked a million times, its like this.
Say Invoice is the base class and InvoiceHistory is the class that simply inherits from Invoice.
When I do something like
invoiceList = session.CreateCriteria(typeof(Invoice)).List();
I get everything from Invoice (that I want, plus everything from InvoiceHistory).
Do I need to have an InvoiceBase and create derived versions for Invoice and InvoiceHistory?
I think this has to do with polymorphism in NHibernate. Try specifying polymorphism="explicit" on the mapping for your base-class (Invoice).
If you don't want to retrieve the invoicehistory for an invoice inheritance wouldn't do the trick. Even creating an InvoiceBase would not help. If you are using inheritance nhibernate will always return the most complex object that exists in database. So if there is a foreign key in the invoicehistory pointing to an invoice you will alway get the invoicehistory object instead of a simple invoice. This is a fundamental feature of nhibernate.
You could excplicitly fetch only the properties of invoice and map them by hand using a ResultTransformer (see Reference for more infos) or create and map a SimpleInvoice object also referencing the invoice table, but with the latter you may face some stales-state issues is you mix Invoice and SimpleInvoice within the same session.
Hope this helps.
I've got a parent and child object. Depending on a value in the parent object changes the table for the child object. So for example if the parent object had a reference "01" then it will look in the following table "Child01" whereas if the reference was "02" then it would look in the table "Child02". All the child tables are the same as in number of columns/names/etc.
My question is that how can I tell Fluent Nhibernate or nhibernate which table to look at as each parent object is unique and can reference a number of different child tables?
I've looked at the IClassConvention in Fluent but this seems to only be called when the session is created rather than each time an object is created.
I found only two methods to do this.
Close and recreate the nhibernate session every time another dynamic table needs to be looked at. On creating the session use IClassConvention to dynamically calculate the name based on user data. I found this very intensive as its a large database and a costly operation to create the session every time.
Use POCO object for these tables with custom data access.
As statichippo stated I could use a basechild object and have multiple child object. Due to the database size and the number of dynamic table this wasn't really a valid option.
Neither of my two solutions I was particularly happy with but the POCO's seemed the best way for my problem.
NHibernate is intended to be an object relational mappers. It sounds like you're doing more of a scripting style and hoping to map your data instead of working in an OOP manner.
It sounds like you have the makings of an class hierarchy though. What it sounds like you're trying to create in your code (and then map accordingly) is a hierarchy of different kinds of children:
BaseChild
--> SmartChild
--> DumbChild
Each child is either smart or dumb, but since they all have a FirstName, LastName, Age, etc, they all are instances of the BaseChild class which defines these. The only differences might be that the SmartChild has an IQ and the DumbChild has a FavoriteFootballTeam (this is just an example, no offense to anyone of course ;).
NHibernate will let you map this sort of relationship in many ways. There could be 1 table that encompasses all classes or (what it sounds like you want in your case), one table per class.
Did I understand the issue/what you're looking for?
I have a table that needs relations to 2 tables, according to ObjectType column.
For example if ObjectType=1 then column Object should point to TABLE1, and if ObjectType=2 then point to TABLE2.
Can I accomplish this in NHibernate mappings or as Fluent NHibernate?
If not will you suggest me using same Interfaces for both Table classes? (Note: table schemas are totally different)
Why not reference both tables, and use one or the other according to your needs in the class code?
Use a property that returns a common interface for both tables and gives one table or the other according to the object type.
I am just starting out with ADO.net Entity Framework I have mapped two tables together and receive the following error:
Error 1 Error 11010: Association End 'OperatorAccess' is not mapped. E:\Visual Studio\projects\Brandi II\Brandi II\Hospitals.edmx 390 11 Brandi II
Not sure what it is I am doing wrong.
I believe I can add some more clarity to the issue (learning as I go):
When I look at the Mapping details and look at the association, the column for operatoraccess table (from above) is blank and the drop down only includes field from the linked table.
The Entity Framework designer is terrible - I've had the same problem many times (and your problem too, Craig):
This happens when you have a many-to-one association which is improperly setup. They could very easily fix the designer to make this process simple; but instead, we have to put up with this crap.
To fix:
Click on the association, and go to the mapping details view.
Under association, click on Maps to <tablename>. Choose the table(s) which make up the many side of the relationship (ie. the table(s) which make up the *-side of the association in the designer)
Under Column, choose the table-columns which map to each entity-side Property. You get this error when one of those entries are blank.
I had the exact same problem and this is what I did to fix it.
Make sure you have an Entity Key set in your designer on the tables your making an association with. Also check that StoreGeneratedPattern is set to Identity for that Entity Key.
There's not a lot of information in your question, but, generally speaking, this means that there is an incompletely defined association. It could be that you have tried to map one table with a foreign key to another table, but have not mapped that other table. You can also get this error when you try to do table per type inheritance without carefully following the steps for implementing that feature.
Not sure of the answer, but I've just posted a similar question, which may at least help clarify the issue you are experiencing.
Defining an Entity Framework 1:1 association
I had to go back into the database itself and clarify the foreign key relationship
I had this problem in the case where I was creating both many to 0..1 and 0..1 to 0..1 associations. One entity needed associations to multiple tables, and that entity did not have foreign keys defined for those tables.
I had to do the table mappings step that is given in the accepted answer, but note that it wasn't only for many to many associations; it applied to all the types of associations I added for this entity.
In the Mapping Details view, I had to select the entity with the non-foreign key ID columns to the various tables. This is not always the "many" side of the relationship. Only there was I able to map the related entity property to the appropriate property in the original entity. Selecting the "destination" entity would not allow me to select the properties that I needed to, and the error would still exist.
So in short, I had to map using the table related to the entity that had the "non-foreign key" ID fields corresponding to the various entities' (and their tables') primary keys that I needed to associate.
Entity A
various other properties...
Id
ContactId
OrderId
etc.
Contact entity
Id
FirstName
LastName
etc.
In the mapping details, I selected Entity A's table. It then showed both ends of the association. I mapped its Entity A's Id property to its table's actual ID column (they had different names). I then mapped the Contact entity's Id field to the ContactId field on the A entity.
Simply select the many relationship table (*) from the Association>Edit Mapping & select the appropriate relationship