IncrementalLoadingCollection always load entire data when page is navigated.

[selastingeorge]

I have been working on a project where I need to load a list of courses from a database using incremental loading. Initially, when I load the page, it loads 30 items as expected. However, when I navigate to another page and come back, the entire list of items is loaded from the database instead of just the next set of 30 items.

It is calling GetPagedItemsAsync multiple times until all the data is loaded.

This is my code.

using CommunityToolkit.Common.Collections;
using Fees_DBASC.Core.Database;
using Fees_DBASC.Models.DataModels;
using MySql.Data.MySqlClient;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace Fees_DBASC.Data.Sources
{
    public class CourseDataSource : IIncrementalSource<Course>
    {
        private readonly List<Course> courseList;

        public CourseDataSource()
        {
            courseList = new List<Course>();

        }

        public async Task<IEnumerable<Course>> GetPagedItemsAsync(int pageIndex, int pageSize, CancellationToken cancellationToken = default)
        {
            using MySqlConnection connection = new MySqlConnection(GlobalDatabaseConfiguration.Url);

            string query = $"SELECT * FROM courses LIMIT @start,@count";
            using MySqlCommand command = new MySqlCommand(query, connection);
            command.Parameters.AddWithValue("@start", pageIndex * pageSize);
            command.Parameters.AddWithValue("@count", pageSize);

            Debug.Write(pageIndex);

            connection.Open();
            using MySqlDataReader reader = (MySqlDataReader)command.ExecuteReader();

            while (reader.Read())
            {
                Course course = new Course
                {
                    Id = reader.GetInt32("id"),
                    Name = reader.GetString("name"),
                    Semesters = reader.GetInt32("semesters"),
                    Timestamp = DateTime.Parse(reader.GetString("timestamp"))
                };

                courseList.Add(course);
            }

            IEnumerable<Course> result = (from course in courseList select course).Skip(pageIndex * pageSize).Take(pageSize);
            return result;
        }
    }
}

I am not sure why it behaves like that, the sample from their docs works perfectly.