EF Core Foreign Key is Reset by Navigation Property when Attaching Disconnected Record to Context - entity-framework-core

Question

I am building a blazor server app using a Syncfusion DataGrid and am having problems updating ForeignKeys that have Navigation Properties. I'm using .Net 6 with Entity Framework Core.
The steps to describe the problem are as follows:
Blazor Page with DataGrid is loaded and initialised with Control Account Data
A record is edited by the user using a Foreign Key Combo Box bound to OBSID_FK. The value is changed from 5 to 10. At this point, the navigation property OBSID is out of date and reflects the old record from OBSID_FK = 5. (Note that the record is not attached to the context at this point as it's in the grid, so change tracker does not detect the change.)
User presses save and retrieve changed records from the grid, ready to save
Create a new context, attach the changed record to the context and save
The problem comes when attaching the disconnected changed record to the context. EFCore detects that there is a mismatch between the FK and Navigation property and automatically resets the FK to from 10 to the original value 5.
My question is: Is it possible to tell EFCore to use the FK value,
rather than the NavigationProperty when resolving conflicts on attaching
disconnected entities to the Context?
Following are selected code extracts.
public partial class ControlAccount
{
[Key]
public Guid GUID {get; set;}
public int ID {get; set;}
public string? Code {get; set;}
public string? Description {get; set;}
public int? OBSID_FK {get; set;}
[ForeignKey("OBSID_FK")] public virtual OBSID? OBSID {get; set;}
}
public partial class OBSID
{
[Key]
public int ID { get; set; }
public string? Code { get; set; }
public string? Description { get; set; }
public string? Comments { get; set; }
}
public class Context :DbContext
{
public Context() : base(GetOptions())
{
}
private static DbContextOptions GetOptions()
{
var options = new DbContextOptionsBuilder().UseSqlServer(XXXXXXXXXXXXX).Options;
return options;
}
protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
{
optionsBuilder.UseLazyLoadingProxies();
}
public DbSet<ControlAccount> ControlAccounts { get; set; }
public DbSet<OBSID> OBSID { get; set; }
}
public class ControlAccountPageTest
{
public void Test()
{
//Retrieve record from db for loading into blazor page
var db = new Context();
var controlAccount = db.ControlAccounts.Include(x => x.OBSID).FirstOrDefault(); //ensure that proxy is loaded
//simulate changing a foreign key value in a drop down box
controlAccount.OBSID_FK = 10; //Change from 5
//simulate retrieving changed record from grid, adding to Context and Saving
using (var db1 = new Context())
{
db1.Update(controlAccount); //***PROBLEM OCCURRS HERE. FOREIGN KEY OBSID_FK = 10 IS OUT OF SYNC WITH NAVIGATION PROPERTY OBSID. EFCORE AUTOMATICALLY RESETS OBSID_FK TO THE NAVIGATION PROPERTY VALUE OF 5
db1.SaveChanges();
}
}
}