I have a table and a view which share the same columns and I'm trying to add them to EDM. I created an abstract entity type and 2 derived types A and B.
Initially I tried creating 2 entity sets, one for each of the derived types, and proceeded to add the EntitySetMapping (using IsTypeOf per MS MSL specifications for EntityTypeMapping of derived type) but got an error in the .edmx file that each of the types doesn't have an entity set and isn't mapped.
To solve this, I created a single EntitySet with type as the base EntityType (the abstract one) and used 2 EntityTypeMapping children tags, specifying the StoreEntitySet as the table or the view accordingly. This resolved the issue but created a single DbSet<BaseType> and now I cannot retrieve data from the view or the table using DbContext.
Any ideas on how to properly solve this?
Thanks
Related
I've been looking at various Code First examples of TPT (Table Per Type) in Entity Framework.
I have an abstract base class with 4 concrete implementations, all of which share the exact same interface. These are being stored using EF in a single table named after the abstract base class.
What I wish to do is use the EF Discriminator column, but without using the automatic table creation in Code First, instead adding the configuration and mappings manually. Does anyone know if this would be possible and if so, what the type of the Discriminator column is (name, type, length, nullable, etc.) so I can create one manually?
Many thanks.
I'm facing two problems by trying to make a model first or code first using TPH concept.
The problem is that I need to use table per hierarchy at three levels, so that:
When I use Model First, the last hierarchy entity (third level) does not saves in database. I create an instance from this entity which inherits an abstract entity, which inherits another abstract entity. The data of two abstract entities are saved, but the last entity not saves. If the inheritance goes at maximum two levels works fine.
If I try to use Code First the problem is that I cannot share attributes with same name, for example: ClassB and ClassC has a property named "Name", and both inherits ClassA. When I map to generate database, I want to create only a sql table called ClassA, but it does not share the column "Name", it creates Name and Name1 columns.
I need to do one of this models works, otherwise I can't use inheritances in my model.
Hope some help!
Thanks
I have an one entity in my edmx model having an one property that can contains huge XML data.
Basically I want to load this entity without this property (column) /* huge data loading */ . And load this column only when it is strictly needed.
I have tried to create an inherited entity containing this property and remove this property from base entity (original entity). I have done mapping.
At this time I have problem, that during compilation a I get error, that base entity is not capable to insert and update itself, because property is not nullable
I am looking for best approach (solution) how this situation should be solved.
I am attaching the cut-out from my emdx designer (containing my current and desired situation)
UPDATE:
I will try to write a procedure that I have tried:
I mapped functions to my custom functions. For entity TRP_TechReport_T without the XML column (property). Then I just mapped for entity TRP_TechReport_T functions to my custom function (containing XML column).
Then I set Mapping condition on the entity TRP_TechReport_T: When TRP_XML = Empty.String
TechReport_T mappings:
TechReport_T functions:
TechReportFull_T mappings:
TechReportFull_T functions:
At this moment I get error:
Error 2 Error 3032: Problem in mapping fragments starting at line 3754:Condition member 'TRP_TechReport_T.TRP_XML' with a condition other than 'IsNull=False' is mapped. Either remove the condition on TRP_TechReport_T.TRP_XML or remove it from the mapping.
The column is not nullable in the database and mustn't be.
I can hard-set XML property to nullable, but in the case of the model updating from the database information will be lost.
At the moment it's the only thing I could think of.
I have very big table in my Database and a can't modify it.
So i have BaseEntity type for table.
I have several children (entity1, entity2) and i'd like to map each type to same column ("Date") and name properties differently.
Surely i can't move all same column properties to base type cause there is about 100 columns in my super table (it's not my design i've jst need to map it)
So i have 0019 error and is there any way to solve it or EF not for me?
No. TPH requires that each property defined in derived entity is exclusive for that entity (no other entity can map to the same column). This targets more general rule in EF - each column can be mapped only once. So if you need to use some column in more entities it must be defined in parent and must have same name in all child entities.
I've a problem mapping just one table from database, I add several tables using "Update model from Database" function through Visual Studio 2010 interface, and everyone works as expected except one table!
Looking at "Model Browser" I can see the table doesn't appear under "Entity Types" but it is present under section "ObjectEntity.Store", so my POCO Generator create an entity related and I can't try to add it again from database but I can't access it through context (like context.table_name).
Tha table doesn't have particular form, there are just two key fields
Could someone help me?
Thanks
I guess it is junction table for implementing many-to-many relation, isn't it? In such case it is correct behavior. EF will hide this table because it is not needed in object oriented approach where many-to-many association can be modeled directly without helper entity. You will see in your model that those two related entities are connected by line with * - * multiplicity and each entity will contain navigation property which is collection of related entities. By manipulation with entities in these collections you are creating or removing records in that hidden table. That is the way how you work with such relation in EF.