.NET6, IServiceProvider, ServiceActivator, 手動注入物件

manually_inject_scope_object.cs

/// ref→[Consuming a scoped service in a background task](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/host/hosted-services?view=aspnetcore-6.0&tabs=visual-studio#consuming-a-scoped-service-in-a-background-task)
※ 手動注入物件

internal class MyConsumeScopedServiceHostedService : BackgroundService
{
    readonly IServiceProvider _provider;
    
    public MyConsumeScopedServiceHostedService(IServiceProvider provider,)
    {
        _provider = provider;
    }

    private async Task DoWork(CancellationToken stoppingToken)
    {
        //※注意：需繞一圈來注入(injection) scope 服務物件。
        /// 因為 BackgroundService 是 singleton 服務物件而 scope 與 singleton 這兩者不能一起注入。
        using var scope = _provider.CreateScope();
        // 注入 scope 服務物件
        var scopedService = scope.ServiceProvider.GetRequiredService<IMyScopedService>();

        //# 終於開始執行工作
        await scopedService.DoWork(stoppingToken);
    }
}

ServiceActivator.cs

using Microsoft.Extensions.DependencyInjection;
using System;

namespace Vista.Biz.AOP
{
    /// <summary>
    /// Add static service resolver to use when dependencies injection is not available
    /// ref → [Resolving instances with ASP.NET Core DI in static classes](https://www.davidezoccarato.cloud/resolving-instances-with-asp-net-core-di-in-static-classes/)
    /// 請在 Startup 把 IServiceProvider 註冊進來使用。
    /// </summary>
    public class ServiceActivator
    {
        //internal static IServiceProvider _serviceProvider = null;
        internal static IServiceProvider _serviceProvider
        {
            get => AppDomain.CurrentDomain.GetData("Host:ServiceProvider") as IServiceProvider;
            set => AppDomain.CurrentDomain.SetData("Host:ServiceProvider", value);
        }

        /// <summary>
        /// Configure ServiceActivator with full serviceProvider
        /// 請在 Program/Startup 執行以把 IServiceProvider 註冊進來使用。
        /// </summary>
        public static void Configure(IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }

        /// <summary>
        /// Create a scope where use this ServiceActivator
        /// </summary>
        public static IServiceScope GetScope(IServiceProvider serviceProvider = null)
        {
            var provider = serviceProvider ?? _serviceProvider;
            return provider?
                .GetRequiredService<IServiceScopeFactory>()
                .CreateScope();
        }
    }
}