.NET Core，.NET5默認配置都是只加載一次，修改配置時都需要重啟才能生效，如何能修改即時生效呢，下面來演示一遍，

一、設定組態檔實時生效

1.1配置

在Program.cs的CreateHostBuilder()處增加加載組態檔的時候，reloadOnChange:true，

這樣組態檔修改的時候，程式就會監聽到檔案發生變化，自動重新加載了，

 public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration((context, config) =>
            {
                config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
            })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();

                });

1.2驗證

appsettings.json檔案內容如下

{
  "TestSetting": "123",
  "AppOptions": {
    "UserName": "zhangsan"
  }
}

代碼：

 public class HomeController : Controller
    {
　　　　 private readonly ILogger<HomeController> _logger;
        private readonly IConfiguration _configuration;
        public HomeController(ILogger<HomeController> logger, IConfiguration configuration)
        {
            _logger = logger;
            _configuration = configuration;
        }

        public IActionResult Index()
        {
            string Name = _configuration["TestSetting"];
            string Name2 = _configuration["AppOptions:UserName"];
            ViewBag.Name = Name;
            ViewBag.Name2 = Name2;
            return View();
        }
}

界面顯示：

 把組態檔修改為：

{
  "TestSetting": "abc",
  "AppOptions": {
    "UserName": "zhangsan123"
  }
}

重繪頁面，已經發生變化：

1.3 IOptions方式實時生效

新建AppOptions.cs類

/// <summary>
    /// 組態檔
    /// </summary>
    public class AppOptions
    {
        public string UserName { get; set; }
    }

在Startup.cs處把配置加到Options

  public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
            services.Configure<AppOptions>(Configuration.GetSection("AppOptions"));
        }

使用：

 public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;
        private readonly IConfiguration _configuration;
        private AppOptions _options;
        public HomeController(ILogger<HomeController> logger, IConfiguration configuration, IOptionsMonitor<AppOptions> appOptions)
        {
            _logger = logger;
            _configuration = configuration;
            _options = appOptions.CurrentValue;
        }

        public IActionResult Index()
        {
            string Name = _configuration["TestSetting"];
            string Name2 = _options.UserName;
            ViewBag.Name = Name;
            ViewBag.Name2 = Name2;
            return View();
        }
}

IOptions有三種方式

//IOptions<T> //站點啟動后，獲取到的值永遠不變
//IOptionsMonitor<T> //站點啟動后，如果組態檔有變化會發布事件 （加載配置時，reloadOnChange:true 必須為true）
//IOptionsSnapshot<T> //站點啟動后，每次獲取到的值都是組態檔里的最新值 （加載配置時，reloadOnChange:true 必須為true）

根據情景使用，這里使用IOptionsMonitor<T>，

1.4多個組態檔加載實時生效

增加多一個db組態檔

修改Program.cs處CreateHostBuilder()，也是加載時加上reloadOnChange:true 就可以了，

  public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
            .ConfigureAppConfiguration((context, config) =>
            {
                config.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
                config.AddJsonFile("Configs/dbsetting.json", optional: true, reloadOnChange: true);
            })
                .ConfigureWebHostDefaults(webBuilder =>
                {
                    webBuilder.UseStartup<Startup>();

                });

使用也是一樣的：

 public class HomeController : Controller
    {
        private readonly ILogger<HomeController> _logger;
        private readonly IConfiguration _configuration;
        private AppOptions _options;
        public HomeController(ILogger<HomeController> logger, IConfiguration configuration, IOptionsMonitor<AppOptions> appOptions)
        {
            _logger = logger;
            _configuration = configuration;
            _options = appOptions.CurrentValue;
        }

        public IActionResult Index()
        {
            string Name = _configuration["TestSetting"];
            string Name2 = _configuration["db:connection1"];
            ViewBag.Name = Name;
            ViewBag.Name2 = Name2;
            return View();
        }
}

標籤：.NET Core

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