選項是配置一個升級版，一般情況下是把一個范圍內(nèi)的配置包裝成類型，以供使用，比如下面的RedisSetting，是Redis的配置參數(shù)：

{"Logging": {"LogLevel": {"Default": "Information","Microsoft.AspNetCore": "Warning"}},"AllowedHosts":?"*",?"RedisSetting": {"Host": "127.0.0.1","Port": 6379,"Password": "123","ConnectionTimeOut": "10ms"} }

可以采用下面的形式把配置類型?實體注入到容器（因為沒有說注入這個知識點，這里可以理解為初始化）中。

var?builder?=?WebApplication.CreateBuilder(); builder.Services.Configure<RedisSetting>(builder.Configuration.GetSection("RedisSetting")); var?app?=?builder.Build();

選項分為三種：普通選項目IOptions，熱更新選項IOptionsSnapshot，監(jiān)控選項IOptionsMonitor，下面分別說明。

IOptions選項

app.MapGet("/appinfo", (IOptions<RedisSetting> options) => {return options.Value; });

Demo結(jié)果

熱加載選項：IOptionsSnapshot

app.MapGet("/snapshot", (IOptionsSnapshot<RedisSetting> options) => {return options.Value; });

結(jié)果

更新配置ConnectionTimeOut為15ms，在不重啟服務(wù)的情況下，再次請求，結(jié)果會變成15ms

監(jiān)控選項：IOptionsMonitor

app.MapGet("/monitorstart", (IOptionsMonitor<RedisSetting> options) => {options.OnChange(redisSetting =>{app.Logger.LogInformation(options.CurrentValue.ToString()); });return "Ok"; });

調(diào)用監(jiān)控

當(dāng)把ConnectionTimeOut更新成20ms時，OnChange會被觸發(fā)，日志會打印出來

利用監(jiān)控特性可以與報警聯(lián)合起來，當(dāng)監(jiān)控到配置有變化時，通知服務(wù)相關(guān)人知曉，是人為設(shè)置，還是被篡改，以便采取措施。

選項命名：

當(dāng)相同的配置有兩組時，選項命名就非常有用了，比如一主一備

"RedisSettings": {"Main": {"Host": "127.0.0.1","Port": 6379,"Password": "123","ConnectionTimeOut": "10ms"},"Prepare": {"Host": "127.0.0.1","Port": 6380,"Password": "456","ConnectionTimeOut": "12ms"}}

實體類可以用靜態(tài)常量區(qū)分開來

public record RedisSetting {public const string Main = "Main";public const string Prepare = "Prepare";public string? Host { get; set; }public int Port { get; set; }public string? Password { get; set; }public string? ConnectionTimeOut { get; set; } }

分別注入配置即可

builder.Services.Configure<RedisSetting>(RedisSetting.Main,builder.Configuration.GetSection("RedisSettings:Main")); builder.Services.Configure<RedisSetting>(RedisSetting.Prepare,builder.Configuration.GetSection("RedisSettings:Prepare"));

不過只有IOptionsSnapshot和IOptionsMonitor能通過Get方法來獲取命名的配置，IOptions沒有實現(xiàn)Get方法

app.MapGet("/snapshotredissetting", (IOptionsSnapshot<RedisSetting> options) => {return options.Get(RedisSetting.Main); }); app.MapGet("/monitorstart", (IOptionsMonitor<RedisSetting> options) => {options.OnChange(redisSetting =>{app.Logger.LogInformation(options.Get(RedisSetting.Main).ToString());app.Logger.LogInformation(options.Get(RedisSetting.Prepare).ToString());});return options.CurrentValue; });

另外，為了提高配置數(shù)據(jù)的安全性，可以給配置選項增加驗證，可以通過在配置實體類上增加DataAnnotations來驗證，也可以自定義驗證

public record RedisSetting {public string? Host { get; set; }public int Port { get; set; }public string? Password { get; set; }[RegularExpression(@"^\d+ms$", ErrorMessage = "格式不正確，必須是ms")]public string? ConnectionTimeOut { get; set; } }

上面的ConnectionTimeOut是DataAnnotations方式，下面是自定義驗證模式。

builder.Services.AddOptions<RedisSetting>().Bind(builder.Configuration.GetSection("RedisSetting")).ValidateDataAnnotations().Validate(config =>{if (config.Port < 1000){return false;}return true;}, "端口不能少于1000");

如果驗證更復(fù)雜，可以自定義類實現(xiàn)，如下：

public class RedisSettingValidation : IValidateOptions<RedisSetting> {public RedisSetting _config { get; init; }public RedisSettingValidation(IConfiguration config){_config = config.GetSection("RedisSetting").Get<RedisSetting>();}public ValidateOptionsResult Validate(string name, RedisSetting options){string? vor=null;var rx = new Regex(@"^((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)$");if (options != null&&options.Host!=null){var match = rx.Match(options.Host);if (string.IsNullOrEmpty(match.Value)){vor = $"{options.Host} 格式不正確";}if (vor != null){return ValidateOptionsResult.Fail(vor);}}return ValidateOptionsResult.Success;} }

添加驗證類型

builder.Services.Configure<RedisSetting>(builder.Configuration.GetSection("RedisSetting")); builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IValidateOptions<RedisSetting>, RedisSettingValidation>());

總結(jié)

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