[英]Dependency Injection in ASP.NET Core Worker Service
我在 .NET Core Worker Service 中遇到了一些依賴注入問題。 請參閱Program.cs
文件中的以下代碼。
public static void Main(string[] args)
{
Log.Logger = new LoggerConfiguration()
.MinimumLevel.Debug()
.MinimumLevel.Override("Microsof)t", LogEventLevel.Warning)
.Enrich.FromLogContext()
.WriteTo.File(@"C:\MyApp_Log\Log.txt")
.CreateLogger();
try
{
Log.Information("Starting up the service.");
CreateHostBuilder(args).Build().Run();
return;
}
catch (Exception ex)
{
Log.Fatal(ex, "There was a problem starting the service");
return;
}
finally
{
Log.CloseAndFlush();
}
}
public static IHostBuilder CreateHostBuilder(string[] args)
{
return Host.CreateDefaultBuilder(args)
.UseWindowsService()
.ConfigureServices((hostContext, services) =>
{
services.AddScoped<IMyAppCoreService, MyAppCoreService>();
services.AddDbContext<MyAppCSContext>(options => options.UseSqlServer("Data Source=xx.xxx.xx.xxx;Database=Mydb;User ID = sa;Password=mypassword"));
services.AddHostedService<Worker>();
})
.UseSerilog();
}
請參閱下面的Worker.cs
文件代碼
private readonly ILogger<Worker> _logger;
private readonly IMyAppCoreService _CoreService;
public Worker(ILogger<Worker> logger, IMyAppCoreService CoreService)
{
_logger = logger;
_CoreService = CoreService;
}
public override Task StartAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("The MyApp_CoreService has been Started...");
return base.StartAsync(cancellationToken);
}
public override Task StopAsync(CancellationToken cancellationToken)
{
_logger.LogInformation("The MyApp_CoreService has been stopped...");
return base.StopAsync(cancellationToken);
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
_logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
_CoreService.CheckAndProcessResult();
await Task.Delay(1000, stoppingToken);
}
}
當我運行上面的查詢時,我得到了下面的查詢。
驗證服務描述符時出錯
ServiceType:MyApp.CS.Business.Facade.IMyAppCoreService Lifetime:Scoped ImplementationType:MyApp.CS.Business.Services.MyAppCoreService':嘗試激活“MyApp”時無法解析“MyApp.CS.Data.Facade.ICommonRepository”類型的服務.CS.Business.Services.MyAppCoreService'。
你能告訴我我哪里做錯了嗎?
編輯:在我用它的 class 注冊所有接口之后。 然后我得到如下新錯誤。
驗證服務描述符“ServiceType:Microsoft.Extensions.Hosting.IHostedService Lifetime:Singleton ImplementationType:MyApp_CoreService.Worker”時出錯:無法使用 Z2ED500A3529637175E675A8791B7C56.E 中的范圍服務“MyApp.CS.Business.Facade.IMyAppCoreService”托管服務”。
您將IMyAppCoreService
作為 Scoped 注入。 Scoped Services 只能由ScopedServiceProvider
。
我的第一個猜測是您不是故意的-您打算將服務注入為 Singleton:
services.AddSingleton<IMyAppCoreService, MyAppCoreService>();
但是,這可能不起作用,因為您使用的是 EF Core,它將其 Context-like 類作為作用域注入。 你有兩個選擇:
services.AddDbContext<YourContext>(opts => { ...config...}, ServiceLifetime.Transient);
將一個名為 ServiceProvider 的IServiceProvider
屬性注入Worker
而不是您的服務。
在 ExecuteAsync 循環中:
_logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
using (var scope = ServiceProvider.CreateScope())
{
scope.ServiceProvider.GetRequiredService<IMyAppCoreService>().CheckAndProcessResult();
}
await Task.Delay(1000, stoppingToken);
這將巧妙地處理每個 Loop 的 EFCore-Data Context Object,在我看來是最干凈的選擇。
依賴注入:
services.AddScoped<IMyAppCoreService, MyAppCoreService>();
services.AddDbContext<MyAppCSContext>(options => options.UseSqlServer("Data Source=xx.xxx.xx.xxx;Database=Mydb;User ID = sa;Password=mypassword"), ServiceLifetime.Scoped);
工人 class:
public class Worker : BackgroundService
{
IServiceProvider _serviceProvider;
public Worker(IServiceProvider serviceProvider)
{
_serviceProvider = serviceProvider;
}
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
using (var scope = _serviceProvider.CreateScope())
{
scope.ServiceProvider.GetRequiredService<IMyAppCoreService>().CheckAndProcessResult();
}
await Task.Delay(1000, stoppingToken);
}
}
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