配置服务时如何通过依赖注入在 Azure Function V3 中注入或使用 IConfiguration

Question

通常在 .NET Core 项目中，我会创建一个“boostrap”类来配置我的服务以及 DI 注册命令。这通常是IServiceCollection 的扩展方法，我可以在其中调用.AddCosmosDbService 之类的方法，并且在包含该方法的静态类中，所有必要的东西都是“自包含的”。但关键是该方法从 Startup 类中获取了一个 IConfiguration。

我过去曾在 Azure Functions 中使用 DI，但尚未遇到此特定要求。

当函数部署在 Azure 中时，我正在使用 IConfiguration 绑定到具有与我的 local.settings.json 以及开发/生产应用程序设置匹配的属性设置的具体类。

CosmosDbClientSettings.cs

/// <summary>
/// Holds configuration settings from local.settings.json or application configuration
/// </summary>    
public class CosmosDbClientSettings
{
    public string CosmosDbDatabaseName { get; set; }
    public string CosmosDbCollectionName { get; set; }
    public string CosmosDbAccount { get; set; }
    public string CosmosDbKey { get; set; }
}

BootstrapCosmosDbClient.cs

public static class BootstrapCosmosDbClient
{
    /// <summary>
    /// Adds a singleton reference for the CosmosDbService with settings obtained by injecting IConfiguration
    /// </summary>
    /// <param name="services"></param>
    /// <param name="configuration"></param>
    /// <returns></returns>
    public static async Task<CosmosDbService> AddCosmosDbServiceAsync(
        this IServiceCollection services,
        IConfiguration configuration)
    {
        CosmosDbClientSettings cosmosDbClientSettings = new CosmosDbClientSettings();
        configuration.Bind(nameof(CosmosDbClientSettings), cosmosDbClientSettings);

        CosmosClientBuilder clientBuilder = new CosmosClientBuilder(cosmosDbClientSettings.CosmosDbAccount, cosmosDbClientSettings.CosmosDbKey);
        CosmosClient client = clientBuilder.WithConnectionModeDirect().Build();
        CosmosDbService cosmosDbService = new CosmosDbService(client, cosmosDbClientSettings.CosmosDbDatabaseName, cosmosDbClientSettings.CosmosDbCollectionName);
        DatabaseResponse database = await client.CreateDatabaseIfNotExistsAsync(cosmosDbClientSettings.CosmosDbDatabaseName);
        await database.Database.CreateContainerIfNotExistsAsync(cosmosDbClientSettings.CosmosDbCollectionName, "/id");

        services.AddSingleton<ICosmosDbService>(cosmosDbService);

        return cosmosDbService;
    }
}

Startup.cs

public class Startup : FunctionsStartup
{

    public override async void Configure(IFunctionsHostBuilder builder)
    {
        builder.Services.AddHttpClient();
        await builder.Services.AddCosmosDbServiceAsync(**need IConfiguration reference**); <--where do I get IConfiguration?
    }
}

显然在Startup.cs 中为IConfiguration 添加一个私有字段是行不通的，因为它需要填充一些东西，而且我也读过using DI for IConfiguration isn't a good idea。

我也尝试过使用here 中描述的选项模式并按如下方式实现：

builder.Services.AddOptions<CosmosDbClientSettings>()
    .Configure<IConfiguration>((settings, configuration) => configuration.Bind(settings));

虽然这可以将IOptions<CosmosDbClientSettings> 注入非静态类，但我使用静态类来保存我的配置工作。

关于如何使这项工作或可能的解决方法有什么建议吗？我希望将所有配置保存在一个地方（引导文件）。

Answer 1

从Microsoft.Azure.Functions.Extensions 的1.1.0 版开始，您可以执行以下操作：

public class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {
        var configuration = builder.GetContext().Configuration;
        builder.Services.AddCosmosDbService(configuration);
    }
}

不幸的是，它仍然不支持异步配置，因此您仍然必须阻止等待任务完成或使用@Nkosi 回答中描述的技巧。

Answer 2

linked example 设计不佳（在我看来）。它鼓励紧密耦合以及 async-await 和阻塞调用的混合。

IConfiguration 默认情况下作为启动的一部分添加到服务集合中，因此我建议更改您的设计以利用依赖项的延迟解析，以便可以通过构建来解析 IConfiguration IServiceProvider 使用工厂委托。

public static class BootstrapCosmosDbClient {

    private static event EventHandler initializeDatabase = delegate { };

    public static IServiceCollection AddCosmosDbService(this IServiceCollection services) {

        Func<IServiceProvider, ICosmosDbService> factory = (sp) => {
            //resolve configuration
            IConfiguration configuration = sp.GetService<IConfiguration>();
            //and get the configured settings (Microsoft.Extensions.Configuration.Binder.dll)
            CosmosDbClientSettings cosmosDbClientSettings = configuration.Get<CosmosDbClientSettings>();
            string databaseName = cosmosDbClientSettings.CosmosDbDatabaseName;
            string containerName = cosmosDbClientSettings.CosmosDbCollectionName;
            string account = cosmosDbClientSettings.CosmosDbAccount;
            string key = cosmosDbClientSettings.CosmosDbKey;

            CosmosClientBuilder clientBuilder = new CosmosClientBuilder(account, key);
            CosmosClient client = clientBuilder.WithConnectionModeDirect().Build();
            CosmosDbService cosmosDbService = new CosmosDbService(client, databaseName, containerName);

            //async event handler
            EventHandler handler = null;
            handler = async (sender, args) => {
                initializeDatabase -= handler; //unsubscribe
                DatabaseResponse database = await client.CreateDatabaseIfNotExistsAsync(databaseName);
                await database.Database.CreateContainerIfNotExistsAsync(containerName, "/id");
            };
            initializeDatabase += handler; //subscribe
            initializeDatabase(null, EventArgs.Empty); //raise the event to initialize db

            return cosmosDbService;
        };
        services.AddSingleton<ICosmosDbService>(factory);
        return service;
    }
}

请注意为避免在非异步事件处理程序中使用 async void 而采取的方法。

参考Async/Await - Best Practices in Asynchronous Programming。

所以现在Configure 可以正常调用了。

public class Startup : FunctionsStartup {

    public override void Configure(IFunctionsHostBuilder builder) =>
        builder.Services
            .AddHttpClient()
            .AddCosmosDbService();
}

Answer 3

这是一个我能够制作的例子；它建立到Azure App Configuration 的连接以进行集中配置和功能管理。应该能够使用所有 DI 功能，例如 IConfiguration 和 IOptions<T>，就像在 ASP.NET Core 控制器中一样。

NuGet 依赖项

• Install-Package Microsoft.Azure.Functions.Extensions
• Install-Package Microsoft.Extensions.Configuration.AzureAppConfiguration
• Install-Package Microsoft.Extensions.Configuration.UserSecrets

Startup.cs

[assembly: FunctionsStartup(typeof(SomeApp.Startup))]

namespace SomeApp
{
    public class Startup : FunctionsStartup
    {
        public IConfigurationRefresher ConfigurationRefresher { get; private set; }

        public override void Configure(IFunctionsHostBuilder hostBuilder) {
            if (ConfigurationRefresher is not null) {
                hostBuilder.Services.AddSingleton(ConfigurationRefresher);
            }
        }
        public override void ConfigureAppConfiguration(IFunctionsConfigurationBuilder configurationBuilder) {
            var hostBuilderContext = configurationBuilder.GetContext();
            var isDevelopment = ("Development" == hostBuilderContext.EnvironmentName);

            if (isDevelopment) {
                configurationBuilder.ConfigurationBuilder
                    .AddJsonFile(Path.Combine(hostBuilderContext.ApplicationRootPath, $"appsettings.{hostBuilderContext.EnvironmentName}.json"), optional: true, reloadOnChange: false)
                    .AddUserSecrets<Startup>(optional: true, reloadOnChange: false);
            }

            var configuration = configurationBuilder.ConfigurationBuilder.Build();
            var applicationConfigurationEndpoint = configuration["APPLICATIONCONFIGURATION_ENDPOINT"];

            if (!string.IsNullOrEmpty(applicationConfigurationEndpoint)) {
                configurationBuilder.ConfigurationBuilder.AddAzureAppConfiguration(appConfigOptions => {
                    var azureCredential = new DefaultAzureCredential(includeInteractiveCredentials: false);

                    appConfigOptions
                        .Connect(new Uri(applicationConfigurationEndpoint), azureCredential)
                        .ConfigureKeyVault(keyVaultOptions => {
                            keyVaultOptions.SetCredential(azureCredential);
                        })
                        .ConfigureRefresh(refreshOptions => {
                            refreshOptions.Register(key: "Application:ConfigurationVersion", label: LabelFilter.Null, refreshAll: true);
                            refreshOptions.SetCacheExpiration(TimeSpan.FromMinutes(3));
                        });

                    ConfigurationRefresher = appConfigOptions.GetRefresher();
                });
            }
        }
    }
}

Answer 4

我正在使用 .net core 3.1

[assembly: FunctionsStartup(typeof(Startup))]
namespace xxxxx.Functions.Base
{
    [ExcludeFromCodeCoverage]
    public class Startup : FunctionsStartup
    {
        private static IConfiguration _configuration = null;

        public override void Configure(IFunctionsHostBuilder builder)
        {
            var serviceProvider = builder.Services.BuildServiceProvider();
            _configuration = serviceProvider.GetRequiredService<IConfiguration>();

            *** Now you can use _configuration["KEY"] in Startup.cs ***
        }

Answer 5

目前推荐的方式

基于此处的文档https://docs.microsoft.com/en-us/azure/azure-functions/functions-dotnet-dependency-injection

将设置绑定到自定义类

您可以从 Azure 中的 Function settings 以及 local.settings.json 文件中绑定设置以进行本地开发，如下所示：

在 Portal 中设置密钥（注意密钥名称中的: 符号）

并且可以选择在local.settings.json 文件中：

{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet",
    "WebhookHandlerSettings:SecretKey": "AYBABTU"
  }
}

有一个自定义的设置类：

public class WebhookHandlerSettings 
    {
        public string SecretKey { get; set; }
}

使用以下代码添加一个 Startup 类文件：

public class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {
            //bind the settings 
            builder.Services.AddOptions<WebhookHandlerSettings>()
            .Configure<IConfiguration>((settings, configuration) =>
            {
                configuration.GetSection(nameof(WebhookHandlerSettings)).Bind(settings);
            });
            //this is where we use the binded settings (by convention it's an extension method) 
            builder.Services.AddRequestValidation(); 
    }
}

这些设置绑定到您在AddOptions<T> 参数中指定的类。 您需要指定 设置部分，然后是 :，然后是设置键。
框架会将键绑定到名称匹配的属性。

将设置注入服务类

通常我将服务注册组代码放入扩展方法中，如下所示：

    public static class RequestValidatorRegistration
    {
        public static void AddRequestValidation(this IServiceCollection services)
        {
            services.AddScoped<IWebhookRequestValidator>((s) =>
            {
#if DEBUG
                return new AlwaysPassRequestValidator(s.GetService<ILogger<AlwaysPassRequestValidator>>());
#endif
   //you can pass the built in ILogger<T> (**must be generic**), as well as your IOptions<T>

    return new WebhookRequestValidator(s.GetService<ILogger<WebhookRequestValidator>>(), 
        s.GetService<IOptions<WebhookHandlerSettings>>());

            });
        }
    }

额外提示 - 如果您传递内置记录器，则不能仅传递 ILogger 作为服务类型。必须是ILogger<T>，否则无法解析。

最后，在您的自定义服务中，您将依赖项注入到构造函数中：

    public class WebhookRequestValidator : IWebhookRequestValidator
    {
        public WebhookRequestValidator(ILogger<WebhookRequestValidator> log, IOptions<WebhookHandlerSettings> settings)
        {
            this.log = log;
            this.settings = settings.Value;
        }
}

当您将注册的依赖项传递给您的函数类时，您不需要将注入注册到函数类中，因为它会自动解析。
只需从函数类中删除 static 关键字，然后添加一个包含您注册的依赖项的构造函数。