Options pattern in ASP.NET Core

The options pattern uses classes to provide strongly typed access to groups of related settings.

Setup

  1. Install the following libraries
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<PackageReference Include="Microsoft.Extensions.Configuration" Version="6.0.0" />
<PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="6.0.0" />
<PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="6.0.0" />
  1. Create your appsettings.json file - there can be nesting like Services:FooService
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{
  "RedisServer": {
    "ConnectionString": "localhost:6379,allowAdmin=true"
  },
  "Services": {
    "FooService": {
        "Url": "http://localhost:5000"
    }
  }
}
  1. Create the options class file, example RedisServerOptions.
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namespace RedisAdmin.Infrastructure.IntegrationTests.Common
{
    public class RedisServerOptions
    {
        public const string RedisServer = "RedisServer";

        public string ConnectionString { get; set; }
    }
}

For the nested Services:FooService example the const string would be

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namespace RedisAdmin.Infrastructure.IntegrationTests.Common
{
    public class FooServiceOptions
    {
        public const string FooService = "Services:FooService";

        public string Url { get; set; }
    }
}
  1. Populate the file using ConfigurationBuilder
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public class CollectionFixture
{
    private readonly RedisServerOptions _redisServerOptions;

    public CollectionFixture()
    {
        var appSettings = "appsettings.json";

        var configuration = new ConfigurationBuilder()
            .AddJsonFile(appSettings)
            .Build();

        _redisServerOptions = configuration
            .GetSection(RedisServerOptions.RedisServer)
            .Get<RedisServerOptions>();
    }

The example above is manual for integration tests. You can use your applications start up instead and pop the options file into the dependency injection container.

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services
    .Configure<RedisServerOptions>(configuration.GetSection(RedisServerOptions.RedisServer));

This can then be injected into your applications constructor as follows

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public class FooServiceClient : IFooServiceClient
{
    private readonly FooServiceOptions _options;

    public FooServiceClient(IOptions<FooServiceOptions> options)
    {
        _options = options.Value;
    }

References