I created four tables in SQL Server, namely tblEmployee, tblProject, tblRoles and tblAssign. One of the tables is tblAssign which contains only two columns, both being foreign keys, which are related as primary keys in two other tables tblEmployee and tblProject.
When I use ADO.NET Entity framework model in C# project, only the three existing tables barring tblAssign are shown in the Entity diagram, even a class file for this table has not been generated. How to create a entity for tblAssign table in the project?
Related
I've seen very old answers relating to this (and conflicting answers), but I am wondering if it's possible to use 1 base entity to create multiple tables in EF Core.
My specific scenario is this: I have about 110 tables, and I need to preserve the data after they are "deleted".
However, because there are a number of 1-to-1 relationships, I cannot set a delete flag to mark the table as "deleted". I would like to have an "Archive" table for each entity, and on Delete in my repository I would find the entity from the original table, add it to the archive table, then delete it from the original table.
However it seems like EF Core creates tables based solely on the classes the models are themselves and not by the tables that are defined.
Is there any way to get around this without needing to create a separate "archive" model for my 110 existing model classes?
I have a table that links two other tables together. When I import these tables into the edmx file, EF automatically creates a navigation property between the two tables and does not create a entity table for the association. Which is great and useful; however, when doing some complex joins from other various tables it would be far more effective to be able to join off of the association table to limit the number of trips to the database.
I tired a solution where I would remove a table, add the middle table, and then re-add the other table. This worked; however, when building the project I get an error:
Error 3015: Problem in mapping fragments starting at lines 6123, 6490: Foreign key constraint 'fk_Um' from table UserModules (ModuleId) to table Modules (ModuleId):: Insufficient mapping: Foreign key must be mapped to some AssociationSet or EntitySets participating in a foreign key association on the conceptual side.
Is there a way to add in the association table, so I can directly join on it without going through the navigation property?
I created a table in SQL that just contained 2 foreign keys, Which Linked a single Bulk upload entry to many titles. After updating my edmx model.
I noticed there is no table in the diagram.
Just an Association mapped between my title table and my bulkupload table.
There is no table in the diagram so I cannot delete the table.
I cannot add things to the table because there is no connection in the C# Code. '
Does anybody have information on why this is happening and how I can fix and add this table so its able to add entries to it?
You can leave it as an association if you'd like. To add things to you junction table you add things to your Icollection so in pseducode:
BulkEntry.Titles.add(TitleToAdd)
I have a database with two tables, customer and account. Because multiple customers can exist on multiple accounts this is a many to many design.
This is how I designed it in SQL
This works quite nicely as Entity Framework picks up that its a mapping table and just maps Customer to Account as lists on each and hiding the mapping table. Brilliant!
I would like to extend this further to add preferences to a mapping between a customer and an account like such:
Am I right in assuming this is not possible? I have tried adding it to EF model but instead it brings back the mapping table.
Anyone else had any luck with this?
What you have in your first case is a simple many to many relation table, which in Entity Framework results in the collections of entities on one another.
If you want to have a relation to the Preference from your CustomerAccount relation table, the relation becomes complex and it cannot be depicted in the simple relation lists anymore. You need add an entity for your relation CustomerAccount which will have foreign keys on Customer, Account and Preference.
By default EF hides a many to many join table that does not contain additional data than the foreign keys to the joined tables.
Is it possible to tell EF (and the designer) to explicitly create the join table and make it usable in code?
Thanks
No EF designer will not add this entity for you. If you want junction table exposed you must manually delete created relation and add junction table's entity and two one-to-many FK relations. Here are related questions with step by step guide:
How to expose the join table in many to many relation
How to get Entity to Table mapping for many to many relations