Autofac：如何通過構造函數參數將實例注冊為組件

Question

我的項目中有一個服務類，並且我已將上下文類（ClientIntagrationContext）注入到服務類的構造函數中，以在運行時從數據庫中提取數據，如下所示。

 public AppLogsDataWriterService(AppLogsDbConnectionFactory dbFactory, IClientIntagrationContext clientIntagrationContext)  
    {
        this.dbFactory = dbFactory;
        this.clientIntagrationContext = clientIntagrationContext;

        LogLevelThresholdValue = clientIntagrationContext.getApplogSettingsValue().ToString();
    }   

並且在解析Startup.cs文件中的服務類（AppLogsDataWriterService）時，我必須將ClientIntagrationContext類實例作為參數傳遞給“ AppLogsDataWriterService”構造函數，並且嘗試創建默認構造函數，但它會為數據庫上下文拋出NullReference異常。 那么如何在注冊我的注射類時傳遞參數？

在Startup.cs中注冊該類，

 ...
 //IClientIntagrationContext clientIntegrationContext = new ClientIntagrationContext();
        IAppLogsDataWriterService logWriterService = new AppLogsDataWriterService(logDbfactory, _________________?);
        builder.RegisterInstance(logDbfactory);
        builder.RegisterInstance(logWriterService);


        builder.RegisterType<PlatformUserIdProvider>().As<IUserIdProvider>();
        builder.RegisterHubs(typeof(UserNotificationsHub).Assembly);
        var logLevelThreshold = RuntimeConfig.LogLevelThreshold;
        var infoLevel = string.IsNullOrEmpty(logLevelThreshold) ? Level.Info : Level.All.Parse(logLevelThreshold);
        var logWriter = RuntimeConfig.GetConfigValue<bool>("In8.Common.Logging.UseDirectWriter") ? (ILogWriter)new SqlWriter(logWriterService) : new WebWriter();
        builder.RegisterAndSetupLog4NetAppLogsForWebWriter("Core", logWriter: logWriter, threshold: infoLevel); 

Answer 1

您可以使用ContainerBuilder.Register在服務實例化期間解決依賴關系。

例如：

builder.RegisterType<ClientIntegrationContext>().As<IClientIntegrationContext>();
builder.Register(x => new AppLogsDataWriterService(logDbfactory, x.Resolve<IClientIntegrationContext>()).AsSelf();

Answer 2

我們可以立即為參數類創建一個新實例，並在運行時將該實例作為參數傳遞。

 Ex:  var parameter= new ClientIntegrationsLogService(anyParameterInstance);

所以我如下修改了我的代碼，它的工作正常。

IExtClientIntegrationsContext iext = new ExtClientIntegrationsContext(TenantInfo.GetTenantInfoForRequest());
        IClientIntegrationsLogService clientIntegrationContext = new ClientIntegrationsLogService(iext);
        IAppLogsDataWriterService logWriterService = new AppLogsDataWriterService(logDbfactory, clientIntegrationContext, TenantInfo.GetTenantInfoForRequest());

否則，我們可以在“ AppLogsDataWriterService”類中為服務類創建一個新實例。 對於這種方法，無需解析或注冊我們的服務類別。

Ex:
private readonly ClientIntegrationsLogService clientIntegrationsLogService;

Constructor()
{
  clientIntegrationsLogService = new ClientIntegrationsLogService(new 
  ExtClientIntegrationsContext(tenant));
}