What is IOptions in .NET Core and How Does It Work?

Sourabh Dhiman

Hello everyone,

I am trying to understand the IOptions interface in .NET Core. While I understand that it is used for configuration management, I am looking for clarity on the following points:

What exactly is IOptions in .NET Core?
How does it work internally?
How can we use it in a practical scenario, for example, reading app settings or configuration files?
How is IOptions different from IConfiguration?

It would be great if someone could provide a simple example or use case demonstrating how to use IOptions.

2 Replies

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Jignesh Kumar1y ago
Accepted answer
Hello Sourabh,

Answer to your question is,
1. What exactly is IOptions in .NET Core?
  
  In .NET Core, IOptions is a key component of the Options Pattern, a design pattern used for managing application configuration settings. Provided by the Microsoft.Extensions.Options namespace, the IOptions interface facilitates accessing strongly-typed configuration settings throughout the application.
2. How does it work internally?
  
  Internally, IOptions and its related components in .NET Core utilize the dependency injection (DI) system and a structured configuration lifecycle to handle and deliver strongly-typed settings. Here's a summary of how it operates:
3. How can we use it in a practical scenario, for example, reading app settings or configuration files?
  
  Let's look at an example of configuring email settings using a strongly-typed class and reading the configuration from appsettings.json.
```
"Email": {
  "SmtpServer": "smtp.example.com",
  "SmtpPort": 587,
  "SmtpUsername": "[email protected]",
  "SmtpPassword": "password"
}
```
Need to create Mapping class to respective settings, Here we have to create EmailOptions
```
public class EmailOptions
{
    public string SmtpServer { get; set; }
    public int SmtpPort { get; set; }
    public string SmtpUsername { get; set; }
    public string SmtpPassword { get; set; }
}
```
How to use in Program.cs file in .net Core,
```
var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllersWithViews();

string? connectionString = builder.Configuration.GetConnectionString("ConnectionStrings");
builder.Services.Configure(builder.Configuration.GetSection("Email"));
```
How to get values in controller or where ever require?

using IOption we can inject and get the requre values
```
private readonly EmailOptions _options;
public EmployeeController(IOptions options)
{
    _options = options.Value;
}
public IActionResult Index()
{
    var smtpServer = _options.SmtpServer; // Get smtp server values from appsettings
    var smtpPort = _options.SmtpPort // Get smtp port values from appsettings
   
    return View();
}
```
- How is IOptions different from IConfiguration?
  
  Primary Role
  
  IConfiguration : Provides raw access to the configuration data in key-value pairs.
  
  IOption : Facilitates accessing strongly-typed, structured settings.
  
  Scope
  
  IConfiguration : General-purpose configuration abstraction. i.e.(connectionstring)
  
  IOption : Focused on specific, strongly-typed settings. i.e (Email setting as above example)

Jaish Mathews1y ago

I trust the explanation below will be helpful.

What is IOptions in .NET Core?

IOptions is a part of the Microsoft.Extensions.Options namespace in .NET Core. It is used to represent a strongly-typed configuration object. It allows developers to manage and access configuration settings in a structured way by binding them to POCO (Plain Old CLR Object) classes.

How does IOptions work internally?

Internally, IOptions uses the Options Pattern, which works in the following steps:

Binding: Configuration data (typically from appsettings.json, environment variables, or other configuration providers) is bound to a strongly-typed class.
Dependency Injection: The options object is registered in the DI container as a singleton or scoped service. IOptions or IOptionsMonitor is then injected wherever needed.
Retrieval: At runtime, when IOptions is requested, the DI system resolves and provides the bound configuration instance.

The binding process is powered by the ConfigurationBinder class, which maps configuration keys to properties of the target class.

Practical Scenario: Reading App Settings or Configuration Files

Here’s a step-by-step example of using IOptions:

1. Define a Configuration Class

public class MyAppSettings
{
    public string ApplicationName { get; set; }
    public int MaxItemsToDisplay { get; set; }
}

2. Add Configuration in appsettings.json

{
  "MyAppSettings": {
    "ApplicationName": "My Application",
    "MaxItemsToDisplay": 10
  }
}

3. Configure the Options in Program.cs or Startup.cs

builder.Services.Configure(builder.Configuration.GetSection("MyAppSettings"));

4. Inject and Use IOptions in a Service or Controller

using Microsoft.Extensions.Options;

public class MyService
{
    private readonly MyAppSettings _settings;

    public MyService(IOptions options)
    {
        _settings = options.Value; // Access the configuration
    }

    public void DisplaySettings()
    {
        Console.WriteLine($"Application Name: {_settings.ApplicationName}");
        Console.WriteLine($"Max Items: {_settings.MaxItemsToDisplay}");
    }
}

5. Register the Service and Use it

builder.Services.AddTransient();

var app = builder.Build();
using var scope = app.Services.CreateScope();
var myService = scope.ServiceProvider.GetRequiredService();
myService.DisplaySettings();

How is IOptions Different from IConfiguration?

Feature	`IOptions`	`IConfiguration`
Purpose	Strongly-typed configuration model	General-purpose key-value configuration
Binding	Binds configuration to POCO classes	Direct access to configuration values
Dependency Injection	Used with DI via `IOptions` or `IOptionsMonitor`	Injected directly or accessed via `builder.Configuration`
Type Safety	Provides type safety through strongly-typed objects	No type safety; values are strings
Ease of Use	Better for structured configuration	Useful for unstructured or ad-hoc access
Change Monitoring	Supports reloadable configurations using `IOptionsMonitor`	Requires manual change tracking

When to Use IOptions vs. IConfiguration?

Use **IOptions** when you want type-safe and reusable configuration models.
Use **IConfiguration** when you need quick, direct access to configuration values without creating a dedicated POCO class.