ChangeToken sample

FileMonitorExtension.cs

using Microsoft.Extensions.DependencyInjection;

namespace ConsoleApp3
{
    public static class FileMonitorExtension
    {
        public static IServiceCollection AddFileMonitor(this IServiceCollection services)
        {
            return services.AddSingleton<IFileMonitorService, FileMonitorService>();
        }
    }
}

FileMonitorService.cs

using System;
using System.IO;
using System.Linq;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Primitives;

namespace ConsoleApp3
{
    public class FileMonitorService : IFileMonitorService
    {
        private readonly IHostEnvironment _environment;
        public FileMonitorService(
            IHostEnvironment environment)
        {
            _environment = environment;
        }

        public void Initialize(string rootDirectory)
        {
            var files = Directory.GetFiles(rootDirectory, "*.sql", SearchOption.AllDirectories)
                .Select(s => Path.IsPathRooted(s)
                            ? Path.GetRelativePath(Directory.GetCurrentDirectory(), s)
                            : s);
            foreach (var file in files)
            {
                ChangeToken.OnChange(
                    ()=>_environment.ContentRootFileProvider.Watch(file),
                    (state) =>
                    {
                        Console.WriteLine($"file changed: {state}");
                    },
                    file);

                Console.WriteLine($"filePath: {file}");

            }
        }
    }
}

IFileMonitorService.cs

namespace ConsoleApp3
{
    public interface IFileMonitorService
    {
        void Initialize(string rootDirectory);
    }
}

MainProcess.cs

using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.Hosting;

namespace ConsoleApp3
{
    public class MainProcess : IHostedService
    {
        private readonly IFileMonitorService _fileMonitorService;
        public MainProcess(IFileMonitorService fileMonitorService)
        {
            _fileMonitorService = fileMonitorService;
        }

        public async Task StartAsync(CancellationToken cancellationToken)
        {
            await Task.Delay(1000, cancellationToken);
            _fileMonitorService.Initialize(Path.Combine(Directory.GetCurrentDirectory(), "Resources"));
        }

        public async Task StopAsync(CancellationToken cancellationToken)
        {
            await Task.Delay(1000, cancellationToken);
        }
    }
}

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace ConsoleApp3
{
    class Program
    {
        static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureServices((context, services) =>
                                   {
                                       services.AddFileMonitor();
                                       services.AddHostedService<MainProcess>();
                                   });
    }
}