将异步方法作为 Quartz.NET 作业运行并处理对象问题

Question

我在这个上下文中使用 Quartz.NET（需要提到这GrabberContext是一个DbContext扩展类）：

// 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("");
    }

}

该GrabService实施是这样的：

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);
        }
    }
}

但是当执行到达时，line #1我收到此错误：

ObjectContext 实例已被释放，不能再用于需要连接的操作。

请问有什么想法吗？

Answer 1

您正在CrawlNextAsync()从同步方法调用异步方法Execute()。一旦CrawlNextAsync()命中...... await _context，它就会返回，Execute()然后返回，我假设在那个时候GrabJob，因此GrabService，因此GrabberContext，被处置，而继续CrawlNextAsync()继续（并尝试使用处置GrabberContext）。

作为一个简单的修复，您可以尝试更改

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

到

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