Why can you call BeginInvoke more than once on the same delegate instance?

Question

I thought that calling BeginInvoke more than once on the same delegate instance would cause problems, but I tried it out and it works. Why is that?

Is the IAsyncResult object returned with each BeginInvoke called unique instead of each instance of the delegate?

In other words, do I only need one instance of the delegate to spawn multiple calls to its function?

Answer 1

Why would it not work? Each time you call it, it will start executing that delegate's actions on a threadpool thread. Yes, each IAsyncResult will be independent of the others, representing that asynchronous action.

Yes, you only need one instance of the delegate. Note that delegates are immutable - calling BeginInvoke isn't going to change its state. You can safely take a copy of a delegate reference, safe in the knowledge that calling Delegate.Combine etc will always create a new delegate instance, rather than modifying the existing one.

Answer 2

Each call to BeginInvoke triggers a new request onto the .net thread pool.

It is perfectly acceptable to call BeginInvoke multiple times. Each IAsyncResult object is unique to that specific call to BeginInvoke .

Just be careful to make sure that you make a matching call to EndInvoke for every BeginInvoke call you make to make sure the resources are cleaned up.

(Note that each call does not necessarily equate to a thread. BeginInvoke passes the requests to the thread pool, which may queue up the requests if all of the threads in the pool are already in use)

Answer 3

例如，您可能希望有多个线程调用相同的委托实例，例如，希望它们都执行相同的任务。

Answer 4

Yes.

Each call to BeginInvoke will return a different IAsyncResult , which can be passed to EndInvoke in any order.

You can use the same delegate to make multiple asynchronous calls.