Say I have 3 tables in a Tennis Application (stripped down removing irrelevant info):
Competitions
Id (PK)
Matches
Id (PK)
CompId (FK)
CourtAssignments
CompId (PK),(FK)
CourtNumber (PK)
MatchId (FK), (Unique)
To describe the above:
A match consists of 2 people playing tennis against eachother on a court.
A competition consists of 0 to many matches.
A courtassignment represents a court during a competition (During a single competition, 0 or 1 match may be assigned to a court) Also, a single match can only be played on a single court number, and exists only in a single competition. (so those two fields together form the primary key for the CourtAssignment's table)
Thus the CourtAssignment's MatchId field will ALWAYS be unique or null.
However, when a generate an EF Model from my database. The multiplicity for my CourtAssignment Navigation Property with my Match is *. This should be 0..1.
I am using Visual Studio 2010 beta 2 (with .Net 4 beta 2 and EF 4 beta 2).
I had been using beta 1 and was able to simply change the * to 0..1. However, now having changed to beta 2 since it has a go-live license (porting upgrading my solution worked fine, but re-writing my solution from scratch, I am unable to manuall change * to 0..1 without receiving an error:
Error 113: Multiplicity is not valid in Role 'CourtAssignments' in relationship 'CourtAssignments_MatchId_FK_Matches_Id'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be *.
Question
How can I change the multiplicity to 0..1? I know it is doable since my old solution continues to work that way. I can't seem to make the change in the designer anymore and get completely lost in the edmx file.
Note: I realize changing MatchId to the primary key would generate the correct multiplicity, but I need my primary key to be the composite of [CompId,CourtNumber] as I need to be able to switch which match is on which court on the fly. And obviously it doesn't work changing the primary key.
Thank you to whoever can provide help!
Scott, this isn't the exactl same scenario as you, but it might help:
Unique Keys not recognized by Entity Framework
I think it may be related - perhaps you've got the FK cols exposed in the conceptual model? It seems you can't do a 1 to 0..1 if this is the case.
Related
I'm using entity framework 4.3 model first and can't figure out why I'm not allowed to have a one to zero-to-one association along with a referential constraint.
I have two main problems. I can't force referential integrity (without manual intervention) and my lazy loading doesn't seem to work... all my 1 to many associations are fine.
I basically have two tables, Loans and Contracts. The Contracts table has a scalar field for LoanId.
Until a loan is submitted, it does not have contract data and I chose not to place everything in the same table due to the size of the contract data. Ie. I don't want contract data retrieved from the database unless it is actually required.
I've searched around and can't seem to find any model first information that clearly answers my questions. Any information that may help me understand and clarify my problem would be greatly appreciated.
Regards
Craig
I guess LoanId field is not a primary key in Contracts table. In such case you cannot have such one-to-one relation because EF doesn't support it. When you create LoanId field in Contracts table the only way to force one-to-one relation is to add unique constraint on that field. EF currently doesn't support unique keys (except primary keys) so the only way to create one-to-one relation is to create relation between primary keys (Loan.Id <-> Contract.Id). If you don't follow this you will get error in designer.
I have an linq to entity mapping issue. I have three tables.
Table 1 - ItemsB(ID(key), Part_Number(will be null until built), other item b information)
Table 2 - ItemsA(ID(key), Part_Number(will be null until built), other item a information)
Table 3 - WebItems(Item_id, web item information) *Consists of items from both ItemsB and ItemsA after they are built and pushed over to this table.
ItemsA/ItemsB will have a 1 to 0.1 relationship with WebItems. Part_Number maps to Item_id.
I am using EF4.0.
Problem is after i set up the association/mappings as stated above i get an error message stating: "Problem in mapping fragment at lines so and so: Column [Part_Number] are being mapped in both fragments to different conceptual side properties."
Usually i know what to do in this case. Get rid of the property [Part_Number]. Problem is i need to access [Part_Number] in both ItemsB and ItemsA quite frequently without going to webitems. Not to mention webitems will not always have the [Part_Number] populated at certain points depending upon whether the items have be pushed to webitems.
Does anyone know how to get around this?
Thanks in advance.
As I understand it ItemA and ItemB to WebItem in one-to-one relation. One-to-one relation in EF always demands that relation is build on primary keys and one side is mandatory (principal) because dependent entity will have primary key and foreign key in one column. Once you assign primary key in dependent entity you must have principal entity with the same primary key otherwise you will violate referential integrity defined by foreign key.
The problem is that your Part_Number is primary key and foreign key in the same time. To allow such mapping in EFv4 you must use Foreign Key association instead of Independent association. Here is brief description how to create foreign key association in the designer. Once you define referential constrain get back to mapping window of association and delete the mapping.
I'm having trouble configuring entity relationships when one entity inherits from another. I'm new to ADO Entity Framework -- perhaps someone more experienced has some tips for how this is best done. I'm using .net 4.
Database tables with fields:
Products (int ID, nvarchar Description)
FoodProducts (int ProductID, bit IsHuge)
Flavors (int ID, int FoodProductID, nvarchar Description)
There are constraints between Products and FoodProducts as well as FoodProducts and Flavors.
Using the designer I create a model from the database. The designer seems to get it right, with a 1:0..1 association between Product and FoodProduct entities, and 1:* association between Flavor and FoodProduct. No errors when I save or build.
Next I set FoodProduct entity to inherit from Product entity. Then I get errors concerning relationship between Product and FoodProduct. Ok, starting fresh, I first delete the relationship between Product and FoodProduct before setting the inheritance. But now I get errors about the relationship between FoodProduct and Flavor. So I delete and then recreate that relationship, connecting Flavor.ID to FoodProduct.ProductID. Now I get other errors.
My question is this: Should I instead be creating relationship between Flavor.FoodProductID and Product.ID? If so, I assume I then could (or should) delete the FoodProduct.ProductID property. Since my database will have many of these types of relationships, am I better off first creating the entity model and exporting the tables to SQL, or importing the database schema and then making many tweaks?
My intent is that there will be several types of products, some of which require many additional fields, some of which do not. So there may be zero or one FoodProducts records associated with each Product record. At least by my thinking, the table for each sub-type (FoodProducts) should be able to "borrow" the primary key from Products (as a FK) to uniquely identify each of its records.
You can find a screen capture here: http://img218.imageshack.us/img218/9720/entityframework.jpg (I'd embed the img but haven't earned the requisite rep' yet!)
Well, I deleted the FoodProduct.ProductID field, as it should always return the same value as Product.ID anyway. Then, as you hinted, I had to manually map the Products.ID field to FoodProducts.ProductID field. Errors resolved. I'll write a little code to test functionality. Thanks for the "observations"!
Couple of observations:
FoodProducts needs a primary key (e,g identity - FoodProductID). Are you sure it should be a 1:0..1 between Food and FoodProducts? I would have thought it should be 1:0..*. For this cardinality to work you need a unique PK on this table.
When you setup inheritance for entities, the parent entity's properties are inherited. So FoodProducts will inherit ID from the Product table.
BUT, on the physical model (database), this field still needs to be mapped to a column on the FoodProducts table - which is why you need the identity field.
After you setup inheritance, you still need to map all the columns on the derived tables. My money is on you have not mapped "ID" on FoodProducts to any column.
If you screencapped your model and show the errors you are getting it would be much easier to diagnose the issue.
Using VS 2010 beta 2, ASP.NET MVC.
I tried to create an Entity framework file and got the data from my database.
There were some issues with the relationships, so I started to tweak things around, but I kept getting the following error for simple one-to-one relationships
Error 1 Error 113: Multiplicity is not valid in Role 'UserProfile' in relationship 'FK_UserProfiles_Users'. Because the Dependent Role properties are not the key properties, the upper bound of the multiplicity of the Dependent Role must be *. myEntities.edmx 2024
My Users table is consists of some other many-to-many relationships to other tables, but when I try to make a one-to-one relationship with other tables, that error pops up.
Users Table
UserID
Username
Email
etc..
UserProfiles Table
UserProfileID
UserID (FK for Users Table)
Location
Birthday
For one-to-one relationships, EF expects that the tables are using the same primary key. And really, if it's a true one-to-one they probably should. So in your example, if you make UserID the primary key on the UserProfiles table, your one-to-one will work.
I have a similar issue, but with a sale and layby scenario.
A layby can exist without a sale, and a sale can exist without a layby. This means I have a 0 or 1 to 0 or 1 relationship.
Layby references sale, but layby cannot use the primary key of Sale, and Sale cannot use the primary key of Layby.
I solved the problem by using a 0 or 1 to many relationship, configured the 'Laybys' getter and setter on the sale as private, and then provided my own 'Layby' getter and setter in my POCO.
Make composite primary key set for two columns UserProfileID and UserID
I'm getting more and more frustrated with EF...
I have a table called ExtendedField with:
Record
DocRef
DocType
Name
Record is the primary key
DocRef and DocType are foreign keys used to identify which Ticket they belong to
Name is the key used by the "definition" table to define what the field actually is
So basically I need 2 associations:
One between Ticket and ExtendedField
on ExtendedField.DocRef=ticket.record
and
ExtendedField.docType=HeaderDocType
One between Definition on
ExtendedField.Name=Definition.FieldName
Then I still need Record to be the primary key so I can directly access the fields.
As near as I can tell this is impossible to do in Entity Framework. For every association all the keys need to be mapped together, whereas I need two keys for one association, 1 key for another one and the actual primary key wouldn't be used in any associations.
It doesn't appear that you can define an association between fields that aren't entity keys either.
So is there any way to do this? Am I missing something?
It's a v1, bro. I myself have had some major pain with mapping of key constraints in EF. I hear that better things are coming in v2.