I'm using Entity Framework 4 and with a Database First binding, and EF is not generating the entities for a few of my tables. I'm not getting any errors, and no matter how many times I select the tables to generate from the "Update Model from Database" popup menu on the design surface, the same tables are still missing from the model.
I get no errors in the wizard. They just don't get generated. Any clues?
EF requires a primary key on the table. EF will not map tables for which it can't find or derive a primary key. If all columns are nullable, it can't assume a primary key. If one or more columns are not nullable, EF will evidently derive a primary key for the table.
EF will ignore table without primary keys.
Options I can think of:
Did you check the box next to those tables?
Did you previously add them, then delete their entities but keep the cache of the tables?
If so you can remove them from entity browser window and re-add them
or manually add entities and define the table they map to in mappings window.
Perhaps tables were classified as relations instead of entities?
You can manually add the entities and choose the table they map to in mappings window.
Actually, in my case, it doesn't work because I was using a hierarchyid field as a primary key and EF doesn't work with this field type, so, it didn't import the table, because a valid PK is required.
A possibility is when you're using tables with some different field types, as hierarchy in SQL Server.
Without Primary Key Tables where Skip Automatically on EF, OtherWise You Fix a Value as Not Null.
Related
I have a table defined in a SQL Server database as follows
Columns
MID Int foreign Key
MRUOMID Int foreign Key
All columns in this table are foreign keys and referring to other entities.
I wish to add an Identity column to this table. If I do so and update the EDMX model from the database, I get the following error.
problem in mapping fragments starting at 7462. You must specify mapping for all key properties.
I need an identity column to be added which I can refer to in my Entity model further.
Please let me know on this issues.
Thanks.
While updating, make sure you include the foreign keys too.
I'm an NHibernate developer trying to give Entity Framework a shot in a hobby project. I'm used to specifying mapping data in code using Fluent NHibernate. Pardoning Microsoft's belief that developers shouldn't be allowed to write code, I'm trying to create my mappings using the Entity Framework's visual designer surface (which you get by opening the .edmx file in Visual Studio).
I have no idea how to set up a many-to-many relationship! I have 'updated the model' from the database, but I get two one-to-many relationships with a new entity corresponding to the junction table (which contains only foreign keys and its own primary key).
So far, all attempts at working this out by clicking on the entities and relationships and such have failed. Can anyone give me a pointer?
Your junction table must be what MS calls a 'pure join table' - it must contain only the two foreign keys, and no other columns. In your case, that means you must delete the primary key column.
When you add the association to the model you choose each of your two tables and choose "many" on both sides of the relationship. When this generates the database script a join table with only the two keys will be created for you.
By the way: If you don't like using Model-first and would rather code research "Code-First" development for the Entity Framework. You can also do Database-First if you prefer that.
Before I submit my question, please be aware that I'm working with an existing database owned by a third party vendor, so unfortunately changing the database format is not an option.
Here's the issue: I have an Entity mapped to a database table that has a varchar column that contains one to many foreign keys in csv format. Those foreign keys correspond to the ID's of another Entity type. What I've been doing is writing a function that creates a List of ID's from that csv list and then I search for that Entity through the DBContect object. What I'd like to do is map a relationship between the entities. Is there a way to do that? Thanks!
Unfortunately there is no way to do that without changes in the database. EF is ORM tool but it is still very dependent on correctness of database design. Storing multiple values in single column is breaking even first database normal form. For EF your column containing csv data is single string value and you cannot make relation on that value.
Btw. it is even more complicated because the column cannot represent one-to-many relation in standard relational meaning - that would require dependent entities to contain Id of your master entity, not that master entity contains Ids of all dependent entities.
I have a simple database with 2 main tables with a many to many relationship through a 3rd bridge/join table.
This 3rd table has an extra field besides the two keys required, so that Entity Framework transforms it into a full entity rather than a many to many relationship between the other 2 tables.
I cannot change this third table in the database itself. Is there a way to ignore the extra field so that EF can do what I want, or a way to manually transform the bridge table into a many to many relation?
Yes, update the store schema (SSDL) to remove the additional fields and regenerate the MSL/CSDL. The easiest way to do this is to create your mapping with a DB which doesn't have these fields. It will work fine against the "real" DB at runtime.
I am just getting started with Microsoft's Entity Framework, using it for an MVC project since MS seems to be really pushing it, and I'm running into some issues. In my database there are multiple lookup tables tied to a single table via foreign keys. Within the entity framework I am trying to combine these into one so that I have a simplified single view for this data in my model. However, this doesn't seem possible from the designer view. Is there something obvious I'm missing? Is there a way that I can edit the edmx file manually to produce this sort of model?
At the moment, Foreign keys and lookup tables in Entity Framework are a PAIN.
EF with LINQ makes getting your data super-easy, and on the surface it looks easy to update, but with lookup tables things get difficult (for now... read on...)
I'm not sure how you would "combine" your lookup tables into a single table. If each table contains a different type of "lookup entity" then IMHO they should be represented separately in your EDM. I'm guessing you're having headaches updating a record's foreign keys to the lookup tables. That's because it is a headache.
Changing foreign key values:
MyDBEntities _db = new MyDBEntities();
//get a Person
MyDBEntities.Person person = (from p in _db.Persons
where p.Id = 1
select p).First();
// This sets the foreign key value in the Person table on the PersonType field
person.PersonTypeReference = new EntityKey("MyDBEntities.PersonType", "PersonTypeId", 3)
The next release version of the Entity Framework will have a new concept called "FK Associations." This will bring back the sanity of setting the foreign key value directly rather than having to create and set an EntityKey.
HTH.