[英]Dependency Injection in ASP.NET Core Worker Service
我在 .NET Core Worker Service 中遇到了一些依赖注入问题。 请参阅Program.cs
文件中的以下代码。
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();
}
请参阅下面的Worker.cs
文件代码
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);
}
}
当我运行上面的查询时,我得到了下面的查询。
验证服务描述符时出错
ServiceType:MyApp.CS.Business.Facade.IMyAppCoreService Lifetime:Scoped ImplementationType:MyApp.CS.Business.Services.MyAppCoreService':尝试激活“MyApp”时无法解析“MyApp.CS.Data.Facade.ICommonRepository”类型的服务.CS.Business.Services.MyAppCoreService'。
你能告诉我我哪里做错了吗?
编辑:在我用它的 class 注册所有接口之后。 然后我得到如下新错误。
验证服务描述符“ServiceType:Microsoft.Extensions.Hosting.IHostedService Lifetime:Singleton ImplementationType:MyApp_CoreService.Worker”时出错:无法使用 Z2ED500A3529637175E675A8791B7C56.E 中的范围服务“MyApp.CS.Business.Facade.IMyAppCoreService”托管服务”。
您将IMyAppCoreService
作为 Scoped 注入。 Scoped Services 只能由ScopedServiceProvider
。
我的第一个猜测是您不是故意的-您打算将服务注入为 Singleton:
services.AddSingleton<IMyAppCoreService, MyAppCoreService>();
但是,这可能不起作用,因为您使用的是 EF Core,它将其 Context-like 类作为作用域注入。 你有两个选择:
services.AddDbContext<YourContext>(opts => { ...config...}, ServiceLifetime.Transient);
将一个名为 ServiceProvider 的IServiceProvider
属性注入Worker
而不是您的服务。
在 ExecuteAsync 循环中:
_logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
using (var scope = ServiceProvider.CreateScope())
{
scope.ServiceProvider.GetRequiredService<IMyAppCoreService>().CheckAndProcessResult();
}
await Task.Delay(1000, stoppingToken);
这将巧妙地处理每个 Loop 的 EFCore-Data Context Object,在我看来是最干净的选择。
依赖注入:
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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