配置服务时如何在具有依赖关系注入的Azure Function V3中注入或使用IConfiguration

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。这通常是一种扩展方法，IServiceCollection可以在其中调用类似的方法，.AddCosmosDbService并且在包含该方法的静态类中，所有必需的东西都是“自包含的”。但是关键是该方法IConfiguration从Startup类中。

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

我正在使用IConfiguration绑定到属性与我两个都匹配的具体类local.settings.json当在Azure中部署功能时，以及开发/生产应用程序设置。

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;
    }
}

启动文件

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，为IConfigurationin 添加一个私有字段是Startup.cs行不通的，因为它需要填充一些东西，而且我还读到，将DI用于IConfiguration不是一个好主意。

我还尝试过使用此处描述的选项模式，并按如下方式实现：

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

尽管这可以将注入IOptions<CosmosDbClientSettings>到非静态类中，但我使用的是静态类来保存我的配置工作。

关于如何进行这项工作或可能的解决方法的任何建议？我希望将所有配置都放在一个位置（引导文件）。

该链接的例子是设计不良的（在我看来）。它鼓励紧密耦合以及异步等待和阻塞调用的混合。

IConfiguration在启动过程中，默认情况下，会被添加到服务集合中，因此，我建议您更改设计以利用延迟的依赖关系解析，以便IConfiguration可以IServiceProvider使用工厂委托通过构建来解决这些问题。

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;
    }
}

请注意避免async void在非异步事件处理程序中使用的方法。

参考Async / Await-异步编程最佳实践。

因此，现在Configure可以正确调用了。

public class Startup : FunctionsStartup {

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

这是我能够振作的一个例子。它建立与Azure App Configuration的连接以进行集中配置和功能管理。一个人应该能够使用所有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

启动文件

[assembly: FunctionsStartup(typeof(Startup))]

public class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder hostBuilder) {
        var serviceProvider = hostBuilder.Services.BuildServiceProvider();
        var configurationRoot = serviceProvider.GetService<IConfiguration>();
        var configurationBuilder = new ConfigurationBuilder();
        var appConfigEndpoint = configuration["AppConfigEndpoint"];

        if (configurationRoot is IConfigurationRoot) {
            configurationBuilder.AddConfiguration(configurationRoot);
        }

        if (!string.IsNullOrEmpty(appConfigEndpoint)) {
            configurationBuilder.AddAzureAppConfiguration(appConfigOptions => {
                // possible to run this locally if refactored to use ClientSecretCredential or DefaultAzureCredential
                appConfigOptions.Connect(new Uri(appConfigEndpoint), new ManagedIdentityCredential());
            });
        }

        var configuration = configurationBuilder.Build();

        hostBuilder.Services.Replace(ServiceDescriptor.Singleton(typeof(IConfiguration), configuration));

        // Do more stuff with Configuration here...
    }
}

public sealed class HelloFunction
{
    private IConfiguration Configuration { get; }

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

    [FunctionName("HelloFunction")]
    public void Run([TimerTrigger("0 */1 * * * *")]TimerInfo myTimer, ILogger log) {
        log.LogInformation($"Timer Trigger Fired: 'Hello {Configuration["Message"]}!'");
    }
}