在哪里可以记录 ASP.NET Core 应用程序的启动停止错误事件

注:适用于.NET Core 3.0或更高版本，此答案已过时.请看this answer.

你需要用Microsoft.AspNetCore.Hosting.IApplicationLifetime

    /// <summary>
    /// Triggered when the application host has fully started and is about to wait
    /// for a graceful shutdown.
    /// </summary>
    CancellationToken ApplicationStarted { get; }

    /// <summary>
    /// Triggered when the application host is performing a graceful shutdown.
    /// Requests may still be in flight. Shutdown will block until this event completes.
    /// </summary>
    CancellationToken ApplicationStopping { get; }

    /// <summary>
    /// Triggered when the application host is performing a graceful shutdown.
    /// All requests should be complete at this point. Shutdown will block
    /// until this event completes.
    /// </summary>
    CancellationToken ApplicationStopped { get; }

在Configure个方法中可以获得IApplicationLifetime的实例.另请在此处添加ILoggerFactory:

public void Configure(IApplicationBuilder app, IApplicationLifetime applicationLifetime, ILoggerFactory loggerFactory)
{
    // use applicationLifetime
}

有ILoggerFactory个，你就可以create个ILogger的实例:

var logger = loggerFactory.CreateLogger("StartupLogger"); 

因此，您只需要在Startup类中创建一个属性来持久化ILogger的实例(或者ILoggerFactory，如果您想要为不同的事件创建不同的Ligger实例).总结一下:

public class Startup 
{
    private ILogger _logger;

    public void Configure(IApplicationBuilder app, IApplicationLifetime applicationLifetime, ILoggerFactory loggerFactory) 
    {
        applicationLifetime.ApplicationStopping.Register(OnShutdown);
        ... 
        // add logger providers
        // loggerFactory.AddConsole()
        ...
        _logger = loggerFactory.CreateLogger("StartupLogger");
    }

    private void OnShutdown()
    {
         // use _logger here;
    }
}