运行 作为 Quartz.NET 作业和处理对象问题的异步方法

Question

我在这种情况下使用 Quartz.NET（需要说明 GrabberContext 是 DbContext 扩展 class）：

// configuring Autofac:
var builder = new ContainerBuilder();

// configuring GrabberContext
builder.RegisterType<GrabberContext>()
    .AsSelf()
    .InstancePerLifetimeScope();

// configuring GrabService
builder.RegisterType<GrabService>()
    .AsImplementedInterfaces()
    .InstancePerLifetimeScope();

// configuring Quartz to use Autofac
builder.RegisterModule(new QuartzAutofacFactoryModule());
builder.RegisterModule(new QuartzAutofacJobsModule(typeof(DiConfig).Assembly));

var container = builder.Build();

// configuring jobs:
var scheduler = container.Resolve<IScheduler>();
scheduler.Start();
var jobDetail = new JobDetailImpl("GrabJob", null, typeof(GrabJob));
var trigger = TriggerBuilder.Create()
    .WithIdentity("GrabJobTrigger")
    .WithSimpleSchedule(x => x
        .RepeatForever()
        .WithIntervalInMinutes(1)
    )
    .StartAt(DateTimeOffset.UtcNow.AddSeconds(30))
    .Build();
    scheduler.ScheduleJob(jobDetail, trigger);

这就是工作：

public class GrabJob : IJob {

    private readonly IGrabService _grabService;

    public GrabJob(IGrabService grabService) { _grabService = grabService; }

    public void Execute(IJobExecutionContext context) {
        _grabService.CrawlNextAsync("");
    }

}

GrabService 实现是这样的：

public class GrabService : IGrabService {

    private readonly GrabberContext _context;

    public GrabService(GrabberContext context) {
        _context = context;
    }

    public async Task CrawlNextAsync(string group) {
        try {
            var feed = await _context.MyEntities.FindAsync(someId); // line #1
            // at the line above, I'm getting the mentioned error...
        } catch(Exception ex) {
            Trace.WriteLine(ex.Message);
        }
    }
}

但是当执行到 line #1 时，我得到这个错误：

The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

有什么想法吗？

Answer 1

您正在从同步方法 Execute() 调用异步方法 CrawlNextAsync()。一旦 CrawlNextAsync() 击中 ...await _context...，它会 returns，然后 Execute() 然后 returns，我假设此时 GrabJob，因此 GrabService，因此 GrabberContext，被释放，而 CrawlNextAsync() 中的延续继续（并尝试使用已释放的 GrabberContext）。

作为简单的修复，您可以尝试更改

public void Execute(IJobExecutionContext context) {
    _grabService.CrawlNextAsync("");
}

至

public void Execute(IJobExecutionContext context) {
    _grabService.CrawlNextAsync("").Wait();
}