Article Objectives

By the end of this article, you will:

1. Understand what the Options Pattern is in .NET Core.
2. Learn the importance of strongly-typed configuration using the Options Pattern.
3. Explore a practical use case where static role information is managed via configuration.
4. Review relevant code samples to understand how to implement and use the Options Pattern.
5. Understand the key takeaways for applying the Options Pattern in your projects.

1. What is the Options Pattern?

The Options Pattern in .NET Core is a design pattern used to manage application configuration in a strongly-typed manner. Instead of accessing configuration values directly from the IConfiguration interface, the Options Pattern allows you to bind configuration sections to strongly-typed classes. This makes it easier to manage, validate, and use configuration settings throughout your application.

Key Features:

• Strongly-Typed Classes: Configuration values are mapped to classes, reducing the risk of runtime errors due to typos or incorrect keys.
• Centralized Configuration: Configuration values are managed in one place, typically in appsettings.json.
• Dependency Injection: Configuration classes are injected into services, making them easy to use and test.

2. Why is the Options Pattern Important?

The Options Pattern is important because it promotes strongly-typed configuration, which has several benefits:

• Compile-Time Safety: Since configuration values are mapped to classes, you get compile-time checks, reducing the likelihood of runtime errors.
• Readability and Maintainability: Configuration values are easier to understand and maintain when they are grouped into meaningful classes.
• Testability: Strongly-typed configuration makes it easier to mock and test configuration values in unit tests.

3. Use Case: Managing Static Role Information

Imagine a scenario where your application needs to manage a list of roles (e.g., ADMIN, USER, GUEST) that are static and defined in the appsettings.json file. These role names are used throughout the application, such as for authorization or logging purposes. You could store the role codes in the appsettings.json file along with the role Id. During runtime get the role Id based on role code. Use the role Id then to fetch further details like user role mapping from the database. The Options Pattern is an ideal solution for this scenario.

Example Configuration in appsettings.json:

{
  "RoleInformationOptions": {
    "Roles": [
      {
        "RoleId": "cf755bef-54b0-4117-a51c-36f6d8f9929f",
        "RoleCode": "ADMIN"
      },
      {
        "RoleId": "a1b2c3d4-5678-9101-1121-314151617181",
        "RoleCode": "USER"
      },
      {
        "RoleId": "b2c3d4e5-6789-1011-1213-415161718192",
        "RoleCode": "GUEST"
      }
    ]
  }
}

4. Implementation of the Options Pattern

Step 1: Define the Configuration Classes

Create a class to represent the configuration structure.

using System.Collections.Generic;

namespace Application.Options
{
    public class RoleInformationOption
    {
        public string RoleId { get; set; }//role identifier
        public string RoleCode { get; set; }//role name
    }

    public class RoleInformationOptions
    {
        public List<RoleInformationOption> Roles { get; set; }
    }
}

Step 2: Register the Configuration in Startup.cs

Bind the RoleInformationOptions section from appsettings.json to the RoleInformationOptions class.

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllers();

    // Register options for strongly-typed configuration
    services.AddOptions();
    services.Configure<RoleInformationOptions>(_configuration.GetSection("RoleInformationOptions"));

    // Register application services
    services.AddScoped<IEntityService, EntityService>();
}

Step 3: Inject and Use the Configuration in a Service

Inject the IOptions<RoleInformationOptions> into a service and use it to retrieve role information.

using System.Linq;
using Microsoft.Extensions.Options;

namespace Application.Services
{
    public class EntityService : IEntityService
    {
        private readonly RoleInformationOptions _roleOptions;

        public EntityService(IOptions<RoleInformationOptions> roleOptions)
        {
            _roleOptions = roleOptions.Value;
        }

        public string GetRoleIdByCode(string roleCode)
        {
            var role = _roleOptions.Roles.FirstOrDefault(r => r.RoleCode == roleCode);
            //TODO: make further database call based on RoleId to get additional info
            return role?.RoleId ?? "Role not found";
        }
    }
}

Step 4: Test the Configuration

Use the service in a controller to test the configuration.

using Microsoft.AspNetCore.Mvc;

namespace Web.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class RoleController : ControllerBase
    {
        private readonly IEntityService _entityService;

        public RoleController(IEntityService entityService)
        {
            _entityService = entityService;
        }

        [HttpGet("{roleCode}")]
        public IActionResult GetRoleId(string roleCode)
        {
            var roleId = _entityService.GetRoleIdByCode(roleCode);
            return Ok(new { RoleCode = roleCode, RoleId = roleId });
        }
    }
}

5. Summary

The Options Pattern in .NET Core is a powerful way to manage application configuration. By using strongly-typed classes, you can ensure compile-time safety, improve maintainability, and make your application more testable. In this article, we explored:

• What the Options Pattern is and why it is important.
• A practical use case for managing static role information.
• Step-by-step implementation with relevant code samples.

By applying the Options Pattern, you can simplify configuration management and make your application more robust and maintainable.