net 5 修改配置不重啟自動生效

一、設置配置文件實時生效

1.1配置

在 program.cs 的 createhostbuilder()處增加加載配置文件的時候，reloadonchange:true。

這樣配置文件修改的時候，程式就會監聽到文件發生變化，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 文件內容如下

{
  "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：

把配置文件修改為：

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

刷新頁面，已經發生變化：

1.3 ioptions 方式實時生效

新建 appoptions.cs 類

/// <summary>
/// 配置文件
/// </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 IOptionsMonitor<AppOptions> _options;

    public HomeController(ILogger<HomeController> logger, IConfiguration configuration, IOptionsMonitor<AppOptions> appOptions)
    {
        _logger = logger;
        _configuration = configuration;
        _options = appOptions;
    }

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

ioptions 有三種方式

1. IOptions<T>          //站点启动后，获取到的值永远不变
2. IOptionsMonitor<T>   //站点启动后，如果配置文件有变化会发布事件 （加载配置时，reloadOnChange:true 必须为true）
3. IOptionsSnapshot<T>  //站点启动后，每次获取到的值都是配置文件里的最新值 （加载配置时，reloadOnChange:true 必须为true）

注意：

ioptionsmonitor< t>和 ioptionssnapshot< t>的最大區別是前者可以被其他的 singleton services 使用而後者不可以， 因為前者被註冊為 singleton 而後者是被註冊為 scoped，也就是說文件被修改了前者會立即 reload，而後者是在每個請求才被 reload。

例：

public class HomeController : Controller
{
    private readonly ILogger<HomeController> _logger;
    private UserService _userService;

    public HomeController(ILogger<HomeController> logger, UserService userService)
    {

        _userService = userService;
    }

    public IActionResult Index()
    {
        string Name2 = _userService.GetName();
        ViewBag.Name2 = Name2;
        return View();
    }
}

public class UserService
{
    private IOptionsMonitor<AppOptions> _options;

    public UserService(IOptionsMonitor<AppOptions> appOptions)
    {
        _options = appOptions;
    }

    public string GetName()
    {
        var Name = _options.CurrentValue.UserName;
        return Name;
    }
}

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

上面的 userservice 是單例注入的，通過 ioptionsmonitor< t>的方式是可以實現配置實時刷新的，而 ioptionssnapshot< t>啟動就會報錯。

1.4多個配置文件加載實時生效

增加多一個 db 配置文件

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();
    }
}