Azure Functions -> 无法将 IServiceProvider 或 IFunctionsHostBuilder 注入(inject)工厂类构造函数

Question

我指的是this解释如何在 Azure 函数中实现 DI 的链接。我想实现 Factory我的模式在哪里Factory class在构造工厂对象时应该能够解决其他依赖关系。

这是代码。

public class Startup : FunctionsStartup
{
    public override void Configure(IFunctionsHostBuilder builder)
    {

        System.Console.WriteLine("***************************I am in startup....");
        builder.Services.AddScoped<PayloadProcessorFactory>();
        
        /*  I tried to explicitly add IFunctionsHostBuilder to Services but its not working.
            builder.Services.AddScoped<IFunctionsHostBuilder>((s) =>{
            System.Console.WriteLine("test");                
            return builder;
        });*/

        /*No problem with below two dependencies and are getting injected without any issue*/
        builder.Services
        .AddScoped<IPayloadProcessor,DoctorPayloadProcessor>()
        .AddScoped<DoctorPayloadProcessor>();

        builder.Services
        .AddScoped<IPayloadProcessor,PatientPayloadProcessor>()
        .AddScoped<PatientPayloadProcessor>();
    }
}

这是我的工厂类

public class PayloadProcessorFactory
{
    private readonly IFunctionsHostBuilder builder;
    private readonly ILogger _logger;
    public PayloadProcessorFactory(IFunctionsHostBuilder builder,ILogger<PayloadProcessorFactory> logger)
    {
        _logger = logger;
       this.builder = builder; //Builder is always null
       _logger.LogDebug("Constructing PayloadProcesorFactory");
    }
}

在上面的代码中，builder 的值始终为 null，因此我无法使用以下语句解析依赖项

payloadProcessor = builder.Services.BuildServiceProvider()
                .GetRequiredService<DoctorPayloadProcessor>();

在 Startup.cs我尝试显式添加 IFunctionsHostBuilder到service collection但在那之后，我遇到了以下问题。

Exception has occurred: CLR/System.InvalidOperationException
An exception of type 'System.InvalidOperationException' occurred in Microsoft.Extensions.DependencyInjection.dll but was not handled in user code: 'Unable to resolve service for type 'Microsoft.Azure.WebJobs.Script.IEnvironment' while attempting to activate 'Microsoft.Azure.WebJobs.Script.Configuration.ScriptHostOptionsSetup'.'

问题我该如何注入(inject)IServiceProvider到我的工厂类以构建复杂的对象并解决多个依赖关系？

项目详情

• Dotnet 框架 - netcoreapp2.1
• Azure 函数版本:2.0

Answer 1

以下是 .NET Core 中使用 DI 的工厂模式示例。您不需要注入(inject)服务提供者来解析类。

工厂接口(interface)示例

public interface IFactory
{
    IWorker Create(WorkerType workerType);
}

工厂实现示例

public class Factory: IFactory
{
    private readonly IEnumerable<IWorker> _workers;

    public AuthenticationEngineFactory(IEnumerable<IWorker> workers)
    {
        _workers = workers;
    }

    public IWorker Create(WorkerType workerType)
    {
        var worker = _workers.FirstOrDefault(x => x.WorkerType == workerType);
        if (worker is null) throw new System.ArgumentException($"Worker with type '{workerType}' is not supported.");
        return worker;
    }
}

工作界面示例

public interface IWorker
{
    WorkerType WorkerType { get; } // This can be an enum.
    void DoWork();
}

工作线程实现示例。

public class Worker1Implementation : IWorker
{
     public WorkerType WorkerType => WorkerType.WorkerType1;

     public void DoWork() {}; // Add implementation
}

public class Worker2Implementation : IWorker
{
     public WorkerType WorkerType => WorkerType.WorkerType2;

     public void DoWork() {}; // Add implementation
}

在您的 Startup.cs 函数中

builder.Services.AddSingleton<IFactory, Factory>();
builder.Services.AddScoped<IWorker, Worker1Implementation>();
builder.Services.AddScoped<IWorker, Worker2Implementation>();