Why is EF core 5.0 inserting duplicate records ?

Question

Why is Entity Framework 5.0 inserting duplicate records in the Database in uncertain behavior when using AddAsync() method for adding data.

Answer 1

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.

Answer 2

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();  
  
        }  
  
    }  
}