问题
Is there an elegant way to know when a worker thread is done executing so I can access resources it produced?
For example if the worker thread queried a list of SQL Servers using
ServersSqlDataSourceEnumerator.Instance.GetDataSources();
and saved the result in a DataTable variable, what mechanism can I use to know when this DataTable variable has been populated/is available. I don't want to poll ThreadState; it would be ideal to fire an event when it's done so I can perform actions with the result.
Thanks!
回答1:
You can use a callback mechanism or block on an event to know of completion of an Async operation. See this page for the Asychronous Programming Model in .net - you can call BeginInvoke on any delegate to perform the action in an Async manner.
If you're using the BackgroundWorker type, you can subscribe to the RunWorkerCompleted event.
回答2:
So fire an event :-P
You could also look at using an AutoResetEvent:
http://msdn.microsoft.com/en-us/library/system.threading.autoresetevent.aspx
回答3:
What I do in this instance is get the WorkerThread to call a function after it has completed the work, which will invoke the the UI Thread, which can do the work in which you require.
E.g.
private void SetWorkerThreadToDoWork()
{
WorkerThread.Start();
}
private void MyWorkerThreadWork()
{
//This will be on the WorkerThread (called from WorkerThread.Start())
DoWorkFunc();
WorkComplete();
}
private void WorkComplete()
{
if(InvokeRequired == true)
{
//Do the invoke
}
else
{
//Check work done by worker thread
//e.g. ServersSqlDataSourceEnumerator.Instance.GetDataSources();
}
}
If it's a simple process you're using, I'd go for a BackgroundWorkerThread, this comes with it's own events that are fired when work is complete. But if you require to use a Thread, I would either look in to Asynchronous Callbacks or a similar route to that shown above.
回答4:
You can check my answer on this SO thread
It uses a call back mechanism. When the async operation is done, it will fire the callback method where you can handle the processing that needs to be done post SQL execution.
Use a similar approach to be notified when the asynchronous operation is done.
Hope this helps :)
回答5:
I don't program in C# but here's what I did with Delphi, maybe you can do it as well with C#. I have a TThread descendant, and in the "destroy" event I send a message to its creator saying "hey I'm about to die !". This way its parent (which is the main thread) creates a new one if it needs a new one. To be precise it launches a timer that, when fired, creates a new thread if a new one is needed (sites sucking time (lol) !!).
来源:https://stackoverflow.com/questions/945122/how-can-i-tell-if-a-thread-is-finished-executing-without-polling-threadstate