APP
.NET Core，.NET5默认配置都是只加载一次，修改配置时都需要重启才能生效，如何能修改即时生效呢，下面来演示一遍。
一、设置配置文件实时生效1.1配置
在Program.cs的CreateHostBuilder()处增加加载配置文件的时候，reloadOnChange:true。
这样配置文件修改的时候，程序就会监听到文件发生变化，自动重新加载了。
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验证
appsettings.json文件内容如下
{
"TestSetting": "123",
"AppOptions": {
"UserName": "zhangsan"
}
}代码：
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();
}
}
界面显示：
把配置文件修改为：
{
"TestSetting": "abc",
"AppOptions": {
"UserName": "zhangsan123"
}
}刷新页面，已经发生变化：
1.3 IOptions方式实时生效
新建AppOptions.cs类
/// <summary>
/// 配置文件
/// </summary>
public class AppOptions
{
public string UserName { get; set; }
}
在Startup.cs处把配置加到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有三种方式
//IOptions<T> //站点启动后，获取到的值永远不变
//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）
//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> 的最大区别是前者可以被其他的Singleton Services使用而后者不可以， 因为前者被注册为Singleton 而后者是被注册为Scoped，也就是说文件被修改了前者会立即Reload，而后者是在每个请求才被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是单例注入的，通过IOptionsMonitor<T>的方式是可以实现配置实时刷新的，而IOptionsSnapshot<T>启动就会报错。
1.4多个配置文件加载实时生效
增加多一个db配置文件
修改Program.cs处CreateHostBuilder()，也是加载时加上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>();
});
使用也是一样的：
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();
}
}
本文摘自 ：https://blog.51cto.com/u
