I have a users table and a roles table.
To link the two together I have created a UsersInRoles table which has a foreign key to the Users' UserId and another foreign key to the Roles' RoleName.
However, when I generate an EDMX from the database instead of a separate table for UsersInRoles, an association is created instead. Should I be using this association or should I try to figure out how to get the UsersInRoles table to be generated?
This is the normal behavior of Entity Framework. The tables used to create n - n relationships are not created in the model as entities(The tables used as a middle table to create a relationship between two tables).
Instead you will observe an n to n relationship between Users and Roles entities.
Related
I have one database with multiple schemas and I want to create separate DBContext for each schema. I am using ef core for model creation. In the first schema, I have a table name Company with Primary Key CompanyID and in the second schema, I have a table name User with Foreign key of CompanyID. When I create a model of the second schema it shows below error at package manager console:
"For foreign key User_CompanyID_fkey on table cs.User, unable to model the end of the foreign key on the principal table app.Company. This is usually because the principal table was not included in the selection set."
How I could achieve this, or should I use single DBContext?
I have the following Table Structure
Facility
PK Facility ID
AccountID
Accounts
PK NameID
PK AccountID
I can't touch the DB so my changes need to be in Entity Framework. Essentially the AccountIDs are linked so I want to create an association between them. So when I create an association I map the AccountIDs together, however I can't map FacilityID to anything and NameID to anything so when I save Visual Studio complains that the mapping is not set correctly.
My main question is how do I ignore the mappings for FacilityID and NameID? I've tried added [NotMapped] to both FacilityID and NameID but that does not work. I've also tried creating a scalar property for Facility and Accounts and used the Referntial Constraint to map them however when I try to map the columns under Table Mapping, the columns I added do not show up which causes VS to complain as well.
Here is my table, I removed most of the fields because they are unnecessary
Assuming Account.AccountID is unique (ie no two rows in Account actually have the same AccountID), just declare that as the only Key Property on the Account entity.
The Key of an entity does not have to be declared as the PK in the database. But you can only have one Key per entity (the Key can, of course, have multiple columns, and EF Core does support alternate keys). The entity Key should be unique, and should have a unique index in the database on the corresponding columns, but that's not enforced by EF.
I've created an edmx for my database. In it Entity framework removed a table and instead created an association between two tables because it matches a column name with the primary key in the other table.
I do not want that as there is no real association between those tables. How can I remove that association and get a class for the middle table instead?
Example:
SomeTable
Id int pk
MiddleTable
SomeTableId int fk
SomeCode int
OtherTable
SomeCode int pk
It's the MiddleTable which do not get a class.
Remove one table from the edmx, e.g. OtherTable.
Update model from database and add MiddleTable.
Update model from database and add OtherTable.
When I do this with a similar model I end up with an association between SomeTable and MiddleTable and an unassociated OtherTable. Now you can add/remove associations manually as you wish.
It's normal EF behavior not to create a class for the middle table. This is a so-called many to many association between SomeTable and OtherTable which can be modelled by two collection properties:
SomeTable.OtherTables
OtherTable.SomeTables
The middle table, the junction table, is not really necessary.
It's a bit surprising to me that you say that there is no association between the two tables although, apparently, in the database there are foreign keys. Technically, it is a many to many association.
I have three table in SQL database such as table Person has relation one to many to table member and number has one to many relation to table member .that means member table in this design is junction table and i want do many to many relation between person table and number table for removing member table .but i cant because when i do relation between person and number in my EDMX file and Generate the EDMX model to SQL database .the sql database creates a table between person table and number table has two field such as personId and numberId. i want add Some field to junction table that removed between two tables.for example i need firstname or last name in junction table that i removed .how i alternative a junction table to many to many relation between two table in my EDMX file that the junction table has more field?
If you are using database first simply add all columns you need in junction table and update model from database. EDMX will contain a new Member entity.
If you are using model first you cannot use many to many relation between Person and Number. You must model three entities - Person, Member and Number with the same relations you expect in the database. Once you use generated database from model you will get the database you expect.
Many-to-many relation with hidden junction table in EDMX is only for scenarios where you have a real junction table without any additional data columns.
I have the following tables:
Table Group (
id INT PK,
year INT PK,
name VARCHAR
)
Table Person (
id PK,
GroupID INT,
name VARCHAR
)
The database does not have foreign keys defined so I want to create a manual association from the Person tables GroupID to the Group tables id.
To do this I right click Person and Add an association. I create a Many to One association and everything works. The problem is when I go to add the mapping. Because the Group table has two primary keys entity framework was something from the Person table to map to the year key.
What do I need to do to create the association?
You cannot create such association because EF follows same rules as database. All PK columns from principal entity must exists as FK columns in dependent entity.
The only way can be some database view selecting distinct Groups with Id and Name and mapped as read only entity and build navigation between those two. I didn't try it but I guess it should work. It will have its own disadvantages because you will have two completely unrelated entities for group and the entity related to person will not accept any modification (without mapping custom SQL commands or stored procedures to insert, updated and delete operations).