This is my appsettings.json file:

{
  {
  "User": {
      "Name": "Marco",
      "Level": "developer",
      "Password": "54321"
  },
  "Robot": {
    "Ip": "192.168.2.244",
    "Port": "3111"
  },
  "PLC": {
    "Ip": "192.168.1.1",
    "Port": "5000"
  }
}

Then in my code I wrote a class MyAppSettings:

namespace IOptions_test
{
    public class MyAppSettings
    {
        public UserSettings User { get; set; }
        public RobotSettings Robot { get; set; }
        public PlcSettings PLC { get; set; }
    }

    public class UserSettings
    {
        public string Name { get; set; }
        public string Level { get; set; }
        public string Password { get; set; }
    }

    public class RobotSettings
    {
        public string Ip { get; set; }
        public string Port { get; set; }
    }

    public class PlcSettings
    {
        public string Ip { get; set; }
        public string Port { get; set; }
    }
}

And I have this in my program.cs:

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace IOptions_test
{
    static class Program
    {
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            // Configure services and load configuration
            // ConfigurationBuilder is used to load configuration from a settings.json file.
            var config = new ConfigurationBuilder()
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .Build();

            // Create a new ServiceCollection, which is used for Dependency Injection (DI)
            var services = new ServiceCollection();

            //This registers the Form1 type as a transient service, which means a new instance will be created every time it's requested.
            services.AddTransient<Form1>();

            // Build the ServiceProvider (DI container) from the configured services
            using var serviceProvider = services.BuildServiceProvider();

            // Retrieve the main form (Form1) from the DI container
            var mainForm = serviceProvider.GetRequiredService<Form1>();

            Application.Run(mainForm);
        }
    }
}

I try to inject the settings. The problem is that in the MainForm.cs:

using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Options;

namespace IOptions_test
{
    public partial class Form1 : Form
    {
        // Private field to hold the application settings (MyAppSettings)
        private readonly MyAppSettings _settings;

        // Constructor for Form1 that accepts IOptions<MyAppSettings> to get the settings injected by DI
        public Form1(IOptions<MyAppSettings> settings)
        {
            InitializeComponent();

            // Cast the IOptions object to ensure it's the correct type
            var options = settings as IOptions<MyAppSettings>;

            // Access the Value property to get the actual MyAppSettings object
            _settings = settings.Value;

            // Set the text of label1 to display user and IP information from the settings
            label1.Text = $"User: {_settings.User.Name}, Robot IP: {_settings.Robot.Ip}, PLC IP: {_settings.PLC.Ip}";
        }
    }
}

the _settings remain null and it throws an exception

System.InvalidOperationException: ‘Unable to resolve service for type ‘Microsoft.Extensions.Options.IOptions`1[IOptions_test.MyAppSettings]’ while attempting to activate ‘IOptions_test.Form1’