TravisWhidden TravisWhidden - 3 months ago 59
C# Question

Entity Framework 6 - Missing table with only primary keys referencing different tables

We are learning Entity Framework 6.1 (from NuGet) as we move away from Linq2Sql. We have a small handful of tables that associate two separate tables like shown below.

EF6 Database First generation

DB Diagram:

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Schema Overview:

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When in Visual studios, blank class library, doing a Database First EF6 EDMX file, the diagram only generates TableA and TableC -- the TableB does not get generated.

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Visual Studios View:

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You can see that only TableA and TableC are created. Technically TableB should have been created, because you would want to be able to manage those references.

The Association between A and C shown in the diagram:

enter image description here

I feel like I am missing an option, or misunderstanding a key concept of Entity Framework. Any idea how to have the missing TableB generated with the T4? The EDMX file does show it, but for some reason it doesn't get generated into a .CS file with the two properties indicating the relationship.

The primary reason we need this, is we extended the EF6 T4 template to add some factory patterns to match our existing models. Because it doesnt generate a class for TableB, we dont get the autogenerated code that we are looking for.

Thoughts / suggestions? Thanks.

Answer

Weak entities or join tables will not be generated by EF, you need to configure the relationships manually thru fluent api or using data annotations

As stated on Microsoft's website: under Relationship's convention:

Note:If you have multiple relationships between the same types (for example, suppose you define the Person and Book classes, where the Person class contains the ReviewedBooks and AuthoredBooks navigation properties and the Book class contains the Author and Reviewer navigation properties) you need to manually configure the relationships by using Data Annotations or the fluent API. For more information, see Data Annotations - Relationships and Fluent API - Relationships.

Refer to this link for more information

UPDATED

A workaround will work in case of EDMX ( but it cost maintenance) as follows:

  1. Remove the foreign keys from the join table in the database
  2. Update the EDMX from database
  3. Recreate the foreign keys in the join table

this workaround will work as long as you will not update your Model from database again.

Recommended solution, keep everything as it was generated by EDMX and learn more about how to use crud operation for this case using the following links that was reported "helpful" by the user '@TravisWhidden'

  1. stackoverflow.com/questions/425316
  2. https://www.youtube.com/watch?v=uMQwORSTGX4 ( video)