在.Net Core的AppSettings /配置中处理带有句点的键名

Question

考虑以下appsettings.json文件：

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "Microsoft.Hosting.Lifetime": "Information"
    }
  },
  "AllowedHosts": "*",

  "NumberOfRetries": 5,
  "Option1": "abc",
  "Option2":  "def"

}

为了成功读取NumberOfRetries，可以使用以下类：

public class AppSettings
{
    public int NumberOfRetries { get; set; }
    public string Option1 { get; set; }
    public string Option2 { get; set; }
}

以下是在Startup.cs中的代码：

    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();

        services.AddOptions();

        services.Configure<AppSettings>(Configuration);
    }

现在，假设键名为Number.Of.Retries而不是用下划线进行分隔的NumberOfRetries。

如何修改AppSettings类（或方法本身）以支持这种情况？无法在属性名称中使用句点。

- Joe Schmoe

---

我非常肯定那不会起作用。那有点像有人评论说C#的变量应该像“重试次数”这样一样。生活就是如此。 - Flydog57

像 DataMember(Name=..) 这样的注释被认可吗？如果是，那么应该能够将“Foo.Bar”映射到“FooBar”。 - user2864740

Answer 1

.NET 6中新增了一个名为 "ConfigurationKeyNameAttribute" 的属性，用于解决这个问题：https://github.com/dotnet/runtime/issues/36010。

- killswitch

---

这可能看起来像...[ConfigurationKeyName(name: "SENDGRID_KEY")] public string SendGridKey { get; set; } - Aaron

Answer 2

好的，我想通了。

理想情况下，我只想这样使用 JsonPropertyName:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json.Serialization;
using System.Threading.Tasks;

namespace WebAPICore
{
    public class AppSettings
    {
        [JsonPropertyName("Number.Of.Retries")]
        public int NumberOfRetries { get; set; }
        public string Option1 { get; set; }
        public string Option2 { get; set; }
    }
}

但它不起作用。为什么？他们不使用JSON解析器吗？

因此，我最终采用的解决方案看起来像这样：

    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();

        services.AddOptions();

        services.Configure<AppSettings>(Configuration); // This maps every key that matches existing property name

        services.PostConfigure<AppSettings>(appSettings =>// This maps keys where names don't match existing property names
        {
            appSettings.NumberOfRetries = Configuration.GetValue<int>("Number.Of.Retries");
        }); 
    }

- Joe Schmoe

---

和我给出的示例有什么不同？PostConfigure？ - Patrick Magee

PostConfgure()加上似乎（我没有运行它）你的示例迭代了所有设置，这是不必要的。 - Joe Schmoe

Answer 3

我理解您的观点，我快速查阅了一下，有能力提供自定义逻辑来配置您的选项。我进行了一个快速的原型...

void Main()
{
    string json = @"{
      ""Logging"": {    
        ""LogLevel"": {
        ""Default"": ""Information"",
          ""Microsoft"": ""Warning"",
          ""Microsoft.Hosting.Lifetime"": ""Information""

        }
      },
      ""AllowedHosts"": ""*"",
      ""Number.Of.Retries"":  5
    }";

    using (var doc = System.Text.Json.JsonDocument.Parse(json, new JsonDocumentOptions {  AllowTrailingCommas = true, CommentHandling = JsonCommentHandling.Skip } ))
    {
        using(var stream = new MemoryStream())
        {
            using (var writer = new Utf8JsonWriter(stream))
            {
                doc.WriteTo(writer);
                writer.Flush();
            }       

            stream.Position = 0;

            // Usable code here
            IConfigurationRoot configuration = new ConfigurationBuilder().AddJsonStream(stream).Build();

            var services = new ServiceCollection();

            services.AddOptions<AppSettings>();

            // There is an option to configure it manually here, if it does not fit the convention
            services.Configure<AppSettings>((options) =>
            {
                options.NumberOfRetries = configuration.GetValue<int>("Number.Of.Retries");
            });

            var container = services.BuildServiceProvider();

            using (var scope = container.CreateScope())
            {
                var appSettings = scope.ServiceProvider.GetRequiredService<IOptions<AppSettings>>();

                Console.WriteLine(appSettings.Value.NumberOfRetries);
            }
        }
    }
}

public class AppSettings
{
    public int NumberOfRetries { get; set; }
}  

如果您有特定的设置模式，您可以为自己创建一个自定义设置绑定器来实现您的“约定”。我提供了一个非常基本的示例，处理设置中的“.”。

void Main()
{
    string json = @"{
      ""Logging"": {    
        ""LogLevel"": {
        ""Default"": ""Information"",
          ""Microsoft"": ""Warning"",
          ""Microsoft.Hosting.Lifetime"": ""Information""

        }
      },
      ""AllowedHosts"": ""*"",
      ""Number.Of.Retries"":  5
    }";

    using (var doc = System.Text.Json.JsonDocument.Parse(json, new JsonDocumentOptions {  AllowTrailingCommas = true, CommentHandling = JsonCommentHandling.Skip } ))
    {
        using(var stream = new MemoryStream())
        {
            using (var writer = new Utf8JsonWriter(stream))
            {
                doc.WriteTo(writer);
                writer.Flush();
            }       

            stream.Position = 0;

            // Usable code here
            IConfigurationRoot configuration = new ConfigurationBuilder().AddJsonStream(stream).Build();

            var services = new ServiceCollection();
            services.AddOptions<AppSettings>(); 
            services.AddSingleton<IConfiguration>(configuration);
            services.ConfigureOptions<CustomConfigureOptions>();

            var container = services.BuildServiceProvider();

            using (var scope = container.CreateScope())
            {
                var appSettings = scope.ServiceProvider.GetRequiredService<IOptions<AppSettings>>();

                Console.WriteLine(appSettings);
            }
        }
    }
}

public class AppSettings
{
    public int NumberOfRetries { get; set; }
}

public class CustomConfigureOptions : IConfigureOptions<AppSettings>
{
    private readonly IConfiguration configuration; 

    public CustomConfigureOptions(IConfiguration configuration)
    {
        this.configuration = configuration;
    }

    public void Configure(AppSettings options)
    {
        foreach(var pair in configuration.AsEnumerable())
        {
            foreach(var property in typeof(AppSettings).GetProperties())
            {
                if (property.Name.Equals(pair.Key.Replace(".", "")))
                {
                    property.SetValue(options, configuration.GetValue(property.PropertyType, pair.Key));
                }
            }
        }
    }
}

- Patrick Magee

---

这很可能是唯一可行的解决方案，但您不认为它有点丑陋吗:D？如果我有几个类似的属性，我将不得不显式地将它们映射到每个属性。我真心希望有更好的方法。 - Joe Schmoe

有一个替代方案，但我不确定它是否值得。请查看我提供的详细答案 :) - Patrick Magee

是的，出于这个特定的原因，您可能会喜欢我所给出的扩展答案，它展示了一种更好的做法。 - Patrick Magee

默认配置处理使用Text.Json来解析（或Json.NET）吗？如果是这样，像DateMember（Name = ..）这样的注释是否被尊重？ - user2864740

在.NET5中，appsettings.json绑定行为类似：实际上会忽略[JsonPropertyName("...")]属性，来自appsettings.json文件的值将加载到具有相同名称（不区分大小写）的类属性中。 - apdevelop