ServiceCollection IOptions<> 不会正确绑定

问题描述

我正在尝试绑定一些可配置的设置。这些值是通过 app-settings.local.json 提供的。要绑定到的模型称为可配置设置。我尝试按照一些教程来解决问题：

1. https://andrewlock.net/how-to-use-the-ioptions-pattern-for-configuration-in-asp-net-core-rc2/
2. https://github.com/aspnet/Configuration/issues/411
3. Cannot set Configuration from JSON appsettings file in .NET Core project
4. ServiceCollection returns null for IOptions even though GetSection is working

我已尝试遵循此处给出的建议并将其应用到我自己的应用程序中。经过 4 个小时的尝试，我无法让它工作。要么我缺乏实现这一点所需的基本知识，要么我忽略了一些东西。

我的 ConfigurableSettings 类的结构如下：

    public class ConfigurableSettings
    {
        public AppSettings _AppSettings;
        public DgeSettings _DgeSettings;
        
        public class AppSettings
        {
            [JsonProperty("SoftDelete")] 
            public bool SoftDelete { get; set; }
        }

        public class DgeSettings
        {
            [JsonProperty("zipFileUrl")] 
            public string zipFileUrl { get; set; }

            [JsonProperty("sourceFileUrl")] 
            public string sourceFileUrl { get; set; }
        }
    }

我的 ConfigureServices 的结构如下：

    public static void ConfigureServices(IServiceCollection serviceCollection,string[] args)
        {
            var serviceCollection = new ServiceCollection(); 
            
            serviceCollection.AddOptions();
            
            var configuration = new ConfigurationBuilder()
                                .SetBasePath(Directory.GetCurrentDirectory())
                                .AddJsonFile("app-settings.local.json",true)
                                .AddJsonFile("app-settings.json",false)
                                .Build();

            serviceCollection.Configure<ConfigurableSettings>(options => configuration.GetSection("AppSettings").Bind(options));
            serviceCollection.Configure<ConfigurableSettings>(options => configuration.GetSection("DgeSettings").Bind(options));

            var services = serviceCollection.BuildServiceProvider();
            var options = services.GetService<IOptions<ConfigurableSettings>>();

            serviceCollection.AddLogging(loggingBuilder =>
            {
                loggingBuilder.AddConfiguration(configuration.GetSection("Logging"));
                loggingBuilder.AddConsole();
                loggingBuilder.AddDebug();
            });

            serviceCollection.AddServices(configuration);
            serviceCollection.AddNopCommerceServices(configuration);

            serviceCollection.AddTransient<Comparator>();
            serviceCollection.AddTransient<UpdateManager>();
            serviceCollection.AddTransient<DgeRequestAuthenticator>();
            serviceCollection.AddTransient<ISourceConnector,DgeConnector>();
            serviceCollection.AddTransient<IDestinationConnector,NopCommerceConnector>();
        }

我的 app-settings.local.json 配置如下：

{
  "AppSettings": {
    "SoftDelete": true
  },"DgeSettings": {
    "zipFileUrl" : "www.example-url.com","sourceFileUrl" : "www.example-url.com"
  }
}

当我尝试在类中使用它时，我在构造函数中调用它，如下所示：

private readonly ConfigurableSettings _settings;
        
        public AlphaBetaService(IOptions<ConfigurableSettings> settings)
        {
            _settings = settings.Value;
        }
    

有人可以帮我找出我做错了什么吗？

解决方法

不确定您在项目中如何使用 ConfigureServices 方法，实际上 Startup.cs 中的 ConfigureServices 必须是无参数的或仅采用 IServiceCollection 类型的一个参数。

更改您的 ConfigureServices 如下：

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

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        var configuration = new ConfigurationBuilder()
                            .SetBasePath(Directory.GetCurrentDirectory())
                            .AddJsonFile("app-settings.local.json",true)
                            .Build();
        services.Configure<ConfigurableSettings>(configuration);

        //...
    }
}

同时更改您的模型设计，如下所示：

public class ConfigurableSettings
{
    public AppSettings AppSettings{ get; set; }
    public DgeSettings DgeSettings { get; set; }        
}
public class AppSettings
{
    [JsonProperty("SoftDelete")]
    public bool SoftDelete { get; set; }
}

public class DgeSettings
{
    [JsonProperty("zipFileUrl")]
    public string zipFileUrl { get; set; }

    [JsonProperty("sourceFileUrl")]
    public string sourceFileUrl { get; set; }
}