分析.NET核心配置并修改绑定

Question

我正在构建一个Azure Function应用程序，它需要一些初始配置才能工作。local.settings.json的values部分包含如下属性的键值对：

{
  "IsEncrypted": false,
  "Values": {
    "FUNCTIONS_WORKER_RUNTIME": "dotnet",
    "MyConfiguration:AllowedEmailDomains":  "gmail.com,hotmail.com"
  }
}

我的配置类如下所示：

    public class MyConfiguration
    {
        public List<string> AllowedEmailDomains { get; set; } = null;
    }

我将其绑定如下：

builder.Services.AddOptions<MyConfiguration>().Configure<IConfiguration>((settings, configuration) =>
            {
                configuration.GetSection("MyConfiguration").Bind(settings);
            });

显然，当前，该值绑定为具有单个字符串元素的列表。

这意味着我可以做这样的事情：

builder.Services.AddOptions<MyConfiguration>().Configure<IConfiguration>((settings, configuration) =>
            {
                configuration.GetSection("MyConfiguration").Bind(settings);
                if (settings.AllowedEmailDomains != null) {
                     // split the string and update the property.
                }
            });

我知道我可以在应用程序配置中提供列表的值。然而，我更喜欢有一个单独的长字符串，我自己拆分，这样用户就不需要提供这些设置的负载，并且可以在应用程序配置中坚持一个字段。

有没有更好的方法可以做到这一点，这样我就可以阅读设置并直接进入列表？

Answer 1

您可以使用Singleton进行配置。

public static class GenericSingleton<T> where T : class
{
    static volatile T _instance;
    static object _lock = new object();
    static GenericSingleton()
    {
    }
    public static T Instance
    {
        get
        {
            if (_instance == null)
                lock (_lock)
                {
                    if (_instance == null)
                    {
                        ConstructorInfo constructor = null;
                        try
                        {
                            // Binding flags exclude generic constructors.
                            constructor = typeof(T).GetConstructor(BindingFlags.Instance | BindingFlags.Public, null, new Type[0], null);
                        }
                        catch (Exception exception)
                        {
                            throw new SingletonException(exception.Message);
                        }
                        if (constructor == null || constructor.IsAssembly)
                            // Also exclude internal renderers.
                            throw new SingletonException(string.Format("A private or protected constructor is missing for '{0}'.", typeof(T).Name));
                        _instance = (T)constructor.Invoke(null);
                    }
                }
            return _instance;
        }
    }
}

创建基本配置：

public class BaseAppConfiguration
{
    internal static BaseAppConfiguration BaseConfig => GenericSingleton<BaseAppConfiguration>.Instance;
    private readonly IConfigurationRoot ConfigurationRoot = null;
    public BaseAppConfiguration()
    {
        var builder = new ConfigurationBuilder().SetBasePath(AppContext.BaseDirectory)
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);
        ConfigurationRoot = builder.Build();
    }
    public RedisConfigurationSection RedisTokenConfig()
    {
        return
            new RedisConfigurationSection()
            {
                Host = ConfigurationRoot["RedisTokenConfiguration:host"],
                Port = int.Parse(ConfigurationRoot["RedisTokenConfiguration:port"]),
                Password = ConfigurationRoot["RedisTokenConfiguration:password"],
                DatabaseID = int.Parse(ConfigurationRoot["RedisTokenConfiguration:databaseID"])
            };
    }
    public string GetConnectionString()
    {
        return ConfigurationRoot.GetSection("ConnectionStrings").GetSection("DefaultConnection").Value;
    }
    public string GetDatabaseProvider()
    {
        return ConfigurationRoot.GetSection("ConnectionStrings").GetSection("Provider").Value;
    }
    public string GetAppVersion()
    {
        return ConfigurationRoot.GetSection("Version").Value;
    }
    public EMailConfigurationSection GetEmailConfig()
    {
        return
            new EMailConfigurationSection()
            {
                SmtpServer = ConfigurationRoot["EmailConfiguration:smtpServer"],
                SmtpPort = int.Parse(ConfigurationRoot["EmailConfiguration:smtpPort"]),
                Username = ConfigurationRoot["EmailConfiguration:username"],
                Password = ConfigurationRoot["EmailConfiguration:password"]
            };
    }
}

并为每个应用程序创建附加配置：

public class ExampleAppConfiguration : BaseAppConfiguration
{
    public ExampleAppConfiguration()
    {
    }
    public static ExampleAppConfiguration Config => GenericSingleton<ExampleAppConfiguration>.Instance;
}