Soft-delete, Cannot update identity column?

I Have the following entity, I am trying to apply the concept of soft delete by adding a shadow property ("IsDeleted") when I run my controller I get the following error,

fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (8ms) [Parameters=[@p4='3333', @p0='0001-01-01T00:00:00.0000000+00:00', @p1='True', @p2='2', @p5='0x00000000000007D3' (Size = 8), @p3='3c975d79-6ebd-4a77-9998-feb438f16ddc' (Size = 450)], CommandType='Text', CommandTimeout='180']
      SET NOCOUNT ON;
      UPDATE [PatientsRegistry] SET [DateCreated] = @p0, [IsDeleted] = @p1, [RecordId] = @p2, [UserId] = @p3
      WHERE [PatientFileId] = @p4 AND [RowVersion] = @p5;
      SELECT [RowVersion]
      FROM [PatientsRegistry]
      WHERE @@ROWCOUNT = 1 AND [PatientFileId] = @p4;
System.Data.SqlClient.SqlException (0x80131904): Cannot update identity column 'RecordId'.

Why is EF trying to update my Id column on soft delete?

[Table ("PatientsRegistry")]
    public class PatientRegistry {
        [DatabaseGenerated (DatabaseGeneratedOption.Identity)]
        [Display (Name = "Record Id")]
        public long RecordId { get; set; }

        [Key, DatabaseGenerated (DatabaseGeneratedOption.None)]
        [Display (Name = "Patient File Number")]
        public long PatientFileId { get; set; }
        public DateTimeOffset DateCreated { get; set; }

        [Timestamp]
        public byte[] RowVersion { get; set; }
        public virtual ICollection<PartnerRegistry> Partners { get; set; }
        public string UserId { get; set; }
        public virtual ApplicationUser User { get; set; }

    }

My model builder,

 builder.Entity<PatientRegistry> ()
         .Property<bool> ("IsDeleted");

builder.Entity<PatientRegistry> ()
       .HasQueryFilter (r => EF.Property<bool> (r, "IsDeleted") == false);

and my controller,

 [HttpDelete]
        public async Task<IActionResult> DeletePatient (long fileId) {
            var patient = await repository.GetPatient (fileId);
            if (patient == null) {
                ModelState.AddModelError (string.Empty, "The patient does not exist in the database");
                return StatusCode (404, DataObjectExtentions.FormatErrorResponse (ModelState));
            }
            repository.RemovePatientFromRegistry (patient);
            await unitOfWork.CompleteAsync ();
            SuccessResponseResource response = new SuccessResponseResource {
                // SuccessMessage = patient.FirstName + " " + patient.LastName + " has been deleted successfully!",
                DataResponse = null
            };

            return StatusCode (200, response);
        }

unitOfWork.CompleteAsync() is,

 public async Task CompleteAsync () {
            var audit = new Audit ();
            audit.CreatedBy = ""; // user login Id 
            await context.SaveChangesAsync (audit);

        }

 This is how I am overriding my saving routine,

public override int SaveChanges (bool acceptAllChangesOnSuccess) {
                        OnBeforeSaving ();
                        return base.SaveChanges (acceptAllChangesOnSuccess);
                }

 public override Task<int> SaveChangesAsync (bool acceptAllChangesOnSuccess, CancellationToken cancellationToken = default (CancellationToken)) {
              OnBeforeSaving ();
              return base.SaveChangesAsync (acceptAllChangesOnSuccess, cancellationToken);
            }

private void OnBeforeSaving () {
       foreach (var entry in ChangeTracker.Entries<PatientRegistry> ()) {
          switch (entry.State) {
             case EntityState.Added:
                entry.CurrentValues["IsDeleted"] = false;
                 break;

              case EntityState.Deleted:
                entry.State = EntityState.Modified;
                entry.CurrentValues["IsDeleted"] = true;
                break;
          }
    }