To add navigation property without foreign key in EF Core, DB-first migration with .NET Core Web API

Question

I am working with an existing system and updating it to .NET Core, Web API and EF Core.

The existing system has 2 tables:

Parent table: Id, name, etc..
Child table: Id, ParentId, name, etc..

Though ParentId exists in the child table, there is no foreign key reference, but I want to be able to use include when I query the parent. I have asked not to add FK as part of deleting they are putting -ve values to parentId column. This way they can bring it back and a legacy system was built that way.

Now, in db-first migration how can I specify a navigation property without fk so my EF Core to act relational; or at least return them together. Adding nullable foreign key is not an option as it will break the system when -ve values are added.

I do have suggested for full cleanup of DB and getting rid of -ve values but that involves lots of testing and no deliverable. So long story short how to add navigation property without foreign key in database first migration ?

I tried adding collection and virtual entry in the model, but after migration it got overwritten. I have added this by using HasMany on modelbuilder as per this document - https://learn.microsoft.com/en-us/ef/core/modeling/relationships?tabs=fluent-api%2Cfluent-api-simple-key%2Csimple-key

But scaffolding is overriding my navigation property

score 5 · Accepted Answer · answered May 04 '20 at 04:08

I found out the answer for this.

In EF core 3.x the dbcontext created by DBFrist scaffolding is all partial classes. So I did the following: 1. new partial class for context class - here i added the relationship of navigation property using OnModelCreatingPartial() method. Example below

public partial class dbContext : DbContext
{
    partial void OnModelCreatingPartial(ModelBuilder builder)
    {
        builder.Entity<Packcomponent>()
        .HasOne(p => p.Pack)
        .WithMany(b => b.PackComponent)
        .HasForeignKey(p => p.PackId);
    }
}

extended the partial class in a new file and added navigation property there.


 public partial class Packcomponent
 {
   public Pack Pack { get; set; }
 }
 public partial class Pack
 {
   public List PackComponent { get; set; }
 }

This way upon scaffolding it did not overwrite custom navigation properties and I also could use this properties to do EF operations like .Include() and to save related entities as well. It is pretty awesome!!

To add navigation property without foreign key in EF Core, DB-first migration with .NET Core Web API

1 Answers1