使用 Entity Framework Core 和脚手架处理“动态外键列”

Question

We have some tables in our database-design which include a column named "PK_ID". This columns are from type "uniqueidentifier" (Guid). The uniqueidentifier points to an entity in another table. So it is basically a Foreign Key column.

The special thing is that there is no constraint on this column. So you can put any uniqueidentifier - value in this column. We have an additional "Type"-column to determine to which table the uniqueidentifier is pointing to.

This certainly does not correspond to the good rules of database design, but it is necessary in our application context and that is not the point.

Our poblem:

When we scaffold our DbContext with dotnet ef dbcontext scaffold EF Core does not recognize the relationships to other tables via the "PK_ID" column. That is not surprising either.

But because this, we cannot use the "Include" and "IncludeThen" methods to build SQL-Join queries.

I hope that was somewhat understandable. How best to deal with this within EntityFramework Core? Is there a way to use methods like "Include" anyway?

Answer 1

You can use fluent syntax when querying for this so you can specify how to join

Syntax looks like this: Taken from here: https://entityframework.net/joining )

var data = context.Authors
    .Join(
        context.Books,
        author => author.AuthorId,
        book => book.Author.AuthorId,
        (author, book) => new
        {
            BookId = book.BookId,
            AuthorName = author.Name,
            BookTitle = book.Title
        }
    ).ToList();