选项是配置一个升级版，一般情况下是把一个范围内的配置包装成类型，以供使用，比如下面的RedisSetting，是Redis的配置参数：

{"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类型 实体注入到容器（因为没有说注入这个知识点，这里可以理解为初始化）中。

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

选项分为三种：普通选项目IOptions，热更新选项IOptionsSnapshot，监控选项IOptionsMonitor，下面分别说明。

IOptions选项

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

Demo结果

热加载选项：IOptionsSnapshot

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

结果

更新配置ConnectionTimeOut为15ms，在不重启服务的情况下，再次请求，结果会变成15ms

监控选项：IOptionsMonitor

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

调用监控

当把ConnectionTimeOut更新成20ms时，OnChange会被触发，日志会打印出来

利用监控特性可以与报警联合起来，当监控到配置有变化时，通知服务相关人知晓，是人为设置，还是被篡改，以便采取措施。

选项命名：

当相同的配置有两组时，选项命名就非常有用了，比如一主一备

"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"}}

实体类可以用静态常量区分开来

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; }
}

分别注入配置即可

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

不过只有IOptionsSnapshot和IOptionsMonitor能通过Get方法来获取命名的配置，IOptions没有实现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，为了提高配置数据的安全性，可以给配置选项增加验证，可以通过在配置实体类上增加DataAnnotations来验证，也可以自定义验证

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

上面的ConnectionTimeOut是DataAnnotations方式，下面是自定义验证模式。

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");

如果验证更复杂，可以自定义类实现，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} 格式不正确";}if (vor != null){return ValidateOptionsResult.Fail(vor);}}return ValidateOptionsResult.Success;}
}

添加验证类型

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