How to Access Configuration Values from appsettings.json in ASP.NET Core?

How to read appsettings.json configuration value in ASP.NET Core

Overview

To access configuration data stored in the appsettings.json file in ASP.NET Core, you can use the configuration builder or options mode.

Use Configuration Builder

Method 1: Use ConfigurationBuilder.GetValue()

• Inject the IConfiguration interface into your class or controller.
• Retrieve the value of a specific key using the GetValue method, specifying the type of the value.

Method 2: Use ConfigurationBinder

• Add a ConfigurationBinder instance as a parameter to your method.
• Use the Bind method to bind objects to configuration values.

Use option mode

1. Define configuration class

• Create a C# class that reflects your configuration data structure.
• Each property in these classes should match the corresponding configuration key.

2. Register configuration instance

• In the ConfigureServices method of the startup class, use services.Configure to register the configuration instance.

3. Inject IOptions

• Inject IOptions into your class or controller.
• Use the Value property to access strongly typed configuration objects.

Example

appsettings.json:

<code class="language-json">{
  "ConnectionStrings": {
    "DefaultConnection": "Server=localhost;Database=MyDatabase"
  },
  "AppIdentitySettings": {
    "User": {
      "RequireUniqueEmail": true
    },
    "Password": {
      "RequiredLength": 8
    }
  }
}</code>

Startup.cs:

<code class="language-csharp">public void ConfigureServices(IServiceCollection services)
{
    var connectionStringSection = Configuration.GetSection("ConnectionStrings");
    services.Configure<ConnectionStringSettings>(connectionStringSection);

    var appIdentitySettingsSection = Configuration.GetSection("AppIdentitySettings");
    services.Configure<AppIdentitySettings>(appIdentitySettingsSection);
}</code>

Controller.cs:

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

    public HomeController(IOptions<AppIdentitySettings> appIdentitySettings)
    {
        _appIdentitySettings = appIdentitySettings.Value;
    }

    public IActionResult Index()
    {
        var requiredLength = _appIdentitySettings.Password.RequiredLength;
        // ...
    }
}</code>

Please note that ConnectionStringSettings and AppIdentitySettings in the above code snippet require you to define the corresponding C# classes to match the structure in appsettings.json. These two methods provide flexible ways to access your application configuration. Which method you choose depends on your preference and the complexity of your application.

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