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.
Related
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 have two tables:
User table with primary key UserId.
Follow table with primary key FollowId.
The Follow table has a column called FollowedId which can mean the primary key of several entities, including User, Keyword, City, Business etc.
There is an additional column in the Follow table called FollowedTypeId, this indicates which entity the FollowedId represents.
How can I create a navigation property on the User table and have that automatically populated with all it's related entities in the Follow table?
I've been looking up composite keys and how to map but I'm afraid I've not yet been able to understand how to accomplish this.
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.
I've a database in SQLServer 2008.
I've a table "Table1" with three rows as the primary key and I need to create a relationship with another table "Table2" but I don't want to add the three fields of Table1 in Table2 to be able to create the relationship.
So I've added a new field in Table1 named IdRow of type Int and Indentity=yes and I've created an index of type "Unique Key" for this new field so I can create the relationship based on this new field instead the three others.
So far so good but when I import the two tables into the model in the Entity Framework's model it doesn't recognize the IdRow as unique so I can't create the relationship with Table2 based on this field.
Can someone help me with this?
Is there a workaround to solve this or I've to add the three fields of Table1 in Table2 to create the relationship?
Well, I would do the opposite.
Can't you put the new idRow as the primary key, and add a UNIQUE Constraint on your 3 other fields ?
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).