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.
Related
I have a database table that does not contain true foreign keys. It has two columns that reference the table name and the id of the record in that table. If it were a true foreign key then I could just create a many to many relationship and be on my way but this one has me stumped because of the table name dicriminator. Any help on how I can do this in the fluent API would be great!
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.
Is there a way I can associate two entities in EF if I don't have an explicit foreign key? I have a relationtype column and a relationId, where the relationId is the foreign key to 1 of 2 tables (determined by relationtype). If possible I would like to relate these objects in code, insert the top level entity and have the member populate this relationid.
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 a database with multiple tables, and some basic relationships. Here is an example of the problem I am having:
My Database:
**Org**
ID
Name
etc
**Detail1**
ID
D1name
**Org_Detail1**
Org_ID
Detail1_ID
**Detail2**
ID
D2Name
**Org_Detail2**
Org_ID
Detial1_ID
BooleanField
My problem is, the Org_detail1 table is not showing up in the entity model, but the Org_Details2 table does.
I thought it may have been because the Org_Detail1 table only contains two ID fields that are both primary keys, while the Org_Details2 table contains 2 primary key ID fields as well as a boolean field.
If I add a dummy field to Org_detail1 and update it, it still won't show up and wont allow me to add a new entity relating to the Org_Detail1 table. The table won't even show up in the list, but it is listed under the tables.
Is there any solution to get this table to appear in my model?
Seems like I may just need to completely delete the model and recreate it. Adding dummy fields is the only solution I've found.
Not sure this is an MVC problem.
Does a Detail1 collection turn up in your Org entity and an Org collection show up in your Detail1 entity. This is the normal behaviour for Entity framework for a many to many intersecting table with no other tangible data.
If not then maybe the foreign key constraints are not defined.