.NET Core 控制台程序讀 appsettings.json 、注依賴、配日志、設 IOptions

.NET Core 控制台程序沒有 ASP.NET Core 的 IWebHostBuilder 與 Startup.cs ，那要讀 appsettings.json、注依賴、配日志、設 IOptions 該怎么辦呢？因為這些操作與 ASP.NET Core 無依賴，所以可以自己動手，輕松搞定。

1、讀 appsettings.json ，ConfigurationBuilder 上

var conf = new ConfigurationBuilder()
    .SetBasePath(Directory.GetCurrentDirectory())
    .AddJsonFile("appsettings.json", true, true)
    .AddJsonFile("appsettings.Development.json", true, true)
    .Build();

需要安裝 nuget 包 Microsoft.Extensions.Configuration 、Microsoft.Extensions.Configuration.FileExtensions 、Microsoft.Extensions.Configuration.Json

2、注依賴，IServiceCollection + IServiceProvider 一起來

IServiceCollection services = new ServiceCollection();
//...
services.AddSingleton<CosClient>();
IServiceProvider serviceProvider = services.BuildServiceProvider();
var cosClient = serviceProvider.GetService<CosClient>();

需要安裝 nuget 包 Microsoft.Extensions.DependencyInjection 

3、配日志， AddLogging 與 ILoggingBuilder 肩並肩

services.AddLogging(builder => builder    
    .AddConfiguration(conf.GetSection("Logging"))
    .AddConsole());

需要安裝 nuget 包 Microsoft.Extensions.Logging 、Microsoft.Extensions.Logging.Configuration 、Microsoft.Extensions.Logging.Console

4、設IOptions，AddOptions() 與 Configure<T> 齊步走

services.AddOptions();
services.Configure<CosClientOptions>(conf.GetSection("cosClient"));

需要安裝 nuget 包 Microsoft.Extensions.Options 與 Microsoft.Extensions.Options.ConfigurationExtensions

完整代碼：

class Program
{
    static async Task Main(string[] args)
    {
        var conf = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json", true, true)
            .AddJsonFile("appsettings.Development.json", true, true)
            .Build();

        IServiceCollection services = new ServiceCollection();
        services.AddLogging(builder => builder
            .AddConfiguration(conf.GetSection("Logging"))
            .AddConsole());
        services.AddOptions();
        services.Configure<CosClientOptions>(conf.GetSection("cosClient"));
        services.AddSingleton<CosClient>();

        IServiceProvider serviceProvider = services.BuildServiceProvider();
        var cosClient = serviceProvider.GetService<CosClient>();
    }
}