question

Create a list of PurchaseSaleLog, then before saving using the debugger inspect values to ensure each element in the list is not a duplicate. Finally use AddRangeAsync to perform the add new records.

Here is a conceptual example for working with AddRange (works with AddRangeAsync also). DeviceType is a reference table used in other models. Yes it's not a for statement either but that does not matter. The point is we can set a breakpoint right before the SaveChanges and inspect data in the list which you would do outside the for statement before the save.

After the save all added items will have a key.

 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
 using System.Threading.Tasks;
 using RelationalLevel1.Data;
 using RelationalLevel1.Models;
    
    
 namespace RelationalLevel1.Classes
 {
     public class PopulateOperations
     {
    
         public static async Task People()
         {
             List<DeviceType> deviceTypes = new()
             {
                 new() { Description = "Home phone" },
                 new() { Description = "Work phone" },
                 new() { Description = "Home email" },
                 new() { Description = "Work email" }
             };
    
             List<Person> people = new List<Person>
             {
                 new ()
                 {
                     FirstName = "Karen", LastName = "Payne",
                     Addresses = new List<Address>()
                     {
                         new () {Street = "123 Maple Street", PostalCode = "00022"},
                         new () {Street = "222 Apple street", PostalCode = "00022"},
                     }, 
                     ContactDevices = new List<ContactDevice>()
                     {
                         new () {DeviceTypeId = 1, Value = "503 999-1111"},
                         new () {DeviceTypeId = 3, Value = "karenp@gmail.com"}
    
                     }
                 },
                 new ()
                 {
                     FirstName = "Mary",
                     LastName = "Jones",
                     Addresses = new List<Address>()
                     {
                         new () {Street = "123 Cherry Street", PostalCode = "99999"},
                         new () {Street = "222 High Lane", PostalCode = "67654"},
                         new () {Street = "444 Birch Ave", PostalCode = "98234"},
                     },
                     ContactDevices = new List<ContactDevice>()
                     {
                         new () {DeviceTypeId = 1, Value = "503 555-5151"},
                         new () {DeviceTypeId = 3, Value = "mary@work.net"},
                         new () {DeviceTypeId = 2, Value = "971-987-9832"}
    
                     }
                 }
             };
    
             await using var context = new PersonContext();
             context.AddRange(deviceTypes);
             context.AddRange(people);
    
             await context.SaveChangesAsync();
    
         }
    
     }
 }