我有一个后台任务，在我的 ASP.NET Core应用程序中每隔几秒钟运行一次。它返回以下错误：
An exception occurred while iterating over the results of a query for context type 'ThaiLiveApi.Data.DataContext'.
System.InvalidOperationException: A second operation started on this context before a previous operation completed.
This is usually caused by different threads using the same instance of DbContext.
我认为因为我在作用域中使用数据库上下文，这是不可能的，并且只为该范围使用一个数据库上下文。我错过了什么吗？
这是我的工作代码：
public class FacebookWorker : IHostedService
{
private readonly IServiceScopeFactory _serviceScopeFactory;
private readonly ILogger<FacebookWorker> _logger;
public FacebookWorker(IServiceScopeFactory serviceScopeFactory, ILogger<FacebookWorker> logger)
{
_serviceScopeFactory = serviceScopeFactory;
_logger = logger;
}
private readonly int JobIntervalInSecs = 5;
private Timer _timer;
public Task StartAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
cancellationToken.ThrowIfCancellationRequested();
}
// Invoke the DoWork method every 5 seconds.
_timer = new Timer(callback: async o => await DoWork(o),
state: null, dueTime: TimeSpan.FromSeconds(0),
period: TimeSpan.FromSeconds(JobIntervalInSecs));
return Task.CompletedTask;
}
private async Task DoWork(object state) {
// allow only a certain number of concurrent work. In this case,
// only allow one job to run at a time.
if (State.numberOfActiveJobs < State.maxNumberOfActiveJobs) {
// Update number of running jobs in one atomic operation.
try {
Interlocked.Increment(ref State.numberOfActiveJobs);
_logger.LogInformation("Fetching comments " + DateTime.Now);
using (var scope = _serviceScopeFactory.CreateScope()) {
var facebookService = scope.ServiceProvider.GetRequiredService<IFacebookService>();
await facebookService.FetchAndHandleComments();
}
}
finally {
Interlocked.Decrement(ref State.numberOfActiveJobs);
}
}
}
}
}
我想我是因为我的工人而收到此错误的？这有可能是在我的代码的另一部分引起的吗？
当一个进程启动但最后一个进程未完成时，就会发生这种情况。 尝试在调用 DbContext 时使用 using block。还有一件事 检查您的 DbContext 实例是否静态。