如何在 asp.net core 中配置依赖项

Question

我有一个 ASP.Net Core 2.1 应用程序。我需要注册并注入一些AWS 的依赖项。

目前，实现如下所示：

public abstract class BaseService
{
    protected readonly IConfiguration _configuration;
    protected readonly RegionEndpoint _region;
    protected readonly IAmazonDynamoDB _dynamoClient;
    protected  IPocoDynamo _pocoDynamo;

    public BaseService(IConfiguration configuration)
    {
        _configuration = configuration;
        var awsSettings = configuration.GetSection("AWS");
        _dynamoClient = SetDynamoClient(awsSettings);
        _pocoDynamo = SetPocoDynamoClient();
    }

    protected IAmazonDynamoDB SetDynamoClient(IConfigurationSection configuration)
    {
        AWSCredentials credentials = new BasicAWSCredentials(configuration["AccessKey"], configuration["AccessSecret"]);
        return new AmazonDynamoDBClient(credentials, _region);
    }

    protected IPocoDynamo SetPocoDynamoClient()
    {
        return new PocoDynamo(_dynamoClient);
    }
}

在进行单元测试时，不能因此模拟 AWS 服务。

我想在Startup.csConfigureServices()中注册所有这些依赖项

这是我正在尝试的：

public void ConfigureServices(IServiceCollection services)
{
    AWSCredentials credentials = new BasicAWSCredentials(configuration["AccessKey"], configuration["AccessSecret"]);

    services.AddTransient(IAmazonDynamoDB, (a) =>
         {
             return new AmazonDynamoDBClient(credentials, RegionEndpoint.GetBySystemName(""))
         });
    // here I need to pass the IAmazonDynamoDB to below IOC
    // services.AddSingleton<IPocoDynamo,new PocoDynamo()> ();

    return services;
}

但这会引发错误

错误 CS0119 'IAmazonDynamoDB' 是一种类型，在给定的上下文中无效

这里如何根据需要配置依赖？

谢谢！

Answer 1

使用工厂委托调用注册的服务

public void ConfigureServices(IServiceCollection services) {
    AWSCredentials credentials = new BasicAWSCredentials(configuration["AccessKey"], configuration["AccessSecret"]);
    services.AddTransient<IAmazonDynamoDB>(sp => 
        new AmazonDynamoDBClient(credentials, RegionEndpoint.GetBySystemName(""))
    );

    //here pass the IAmazonDynamoDB to below IOC
    services.AddSingleton<IPocoDynamo>(serviceProvider => {
        var pocoDynamo = new PocoDynamo(serviceProvider.GetRequieredService<IAmazonDynamoDB>());
        pocoDynamo.SomeMethod();
        return pocoDynamo;
    });
}

目标类不再需要依赖IConfiguration，因为可以通过构造函数注入显式注入依赖项。

public abstract class BaseService {
    protected readonly IAmazonDynamoDB dynamoClient;
    protected readonly IPocoDynamo pocoDynamo;

    public BaseService(IAmazonDynamoDB dynamoClient, IPocoDynamo pocoDynamo) {        
        this.dynamoClient = dynamoClient;
        this.pocoDynamo = pocoDynamo;
    }
}