How to Read AppSettings Values from a JSON File in ASP.NET Core?

Accessing Configuration Data from JSON in ASP.NET Core: A Practical Guide

External configuration sources, like JSON files, are frequently used in web development. ASP.NET Core offers robust methods for accessing this data, differing from older versions. This guide demonstrates how to retrieve AppSettings values from a JSON file.

Setting Up the Configuration File

First, create a Config.json file (e.g., within the appsettings folder) with your key-value pairs:

<code class="language-json">{
  "AppSettings": {
    "token": "1234"
  }
}</code>

This file stores the configuration data you'll access in your code.

Integrating JSON Configuration into Your Application

Within your application's Startup.cs file, configure the ConfigurationBuilder:

<code class="language-csharp">public class Startup
{
    public IConfiguration Configuration { get; }

    public Startup(IHostingEnvironment env)
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(env.ContentRootPath)
            .AddJsonFile("appsettings/Config.json", optional: true, reloadOnChange: true);

        Configuration = builder.Build();
    }
    // ... rest of your Startup class
}</code>

Accessing Configuration in Controllers via Dependency Injection

To use these settings in your controllers, inject the IConfiguration object:

<code class="language-csharp">public class HomeController : Controller
{
    private readonly IConfiguration _configuration;

    public HomeController(IConfiguration configuration)
    {
        _configuration = configuration;
    }

    public IActionResult Index()
    {
        var token = _configuration["AppSettings:token"];
        return View(token);
    }
}</code>

Retrieving the value is straightforward using the key path "AppSettings:token".

Enhanced Approach: The Options Pattern (Recommended for ASP.NET Core 2.0 )

For ASP.NET Core 2.0 and later, the Options pattern provides a more structured approach.

Define a class representing your configuration:

<code class="language-csharp">public class AppSettings
{
    public string Token { get; set; }
}</code>

In Startup.cs, configure and inject the IOptions<AppSettings> object:

<code class="language-csharp">services.AddOptions<AppSettings>()
    .Configure<IConfiguration>((settings, configuration) =>
    {
        configuration.GetSection("AppSettings").Bind(settings);
    });</code>

Now, in your controller:

<code class="language-csharp">public class HomeController : Controller
{
    private readonly IOptions<AppSettings> _appSettings;

    public HomeController(IOptions<AppSettings> appSettings)
    {
        _appSettings = appSettings;
    }

    public IActionResult Index()
    {
        var token = _appSettings.Value.Token;
        return View(token);
    }
}</code>

This method offers type safety and improved maintainability compared to the previous approach. It's the preferred method for newer ASP.NET Core projects.

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