C# SocketAsyncEventHandler evaluate operation on Complete

Question

How do you evaluate if a Socket operation was successful or not with SocketAsyncEventArgs? Do you evaluate the SocketAsyncEventArgs you passed as parameter?

SocketasyncEventArgs saea = new SocketAsyncEventArgs();
socket.ConnectAsync(saea);
saea.Completed += (sender, args) => 
{
    if(saea.SocketError != SocketError.Success)
        // fail
}

Or do you evaluate the SocketAsyncEventArgs from the Completed event?

saea.Completed += (sender, args) => 
{
    if(args.SocketError != SocketError.Success)
        // fail
}

Or both? What does it mean if one shows success and the other not?

score 2 · Accepted Answer · answered Dec 05 '19 at 14:32

2

Firstly, note that you need to subscribe the event before you call the *Async method (ConnectAsync in this case), and you must check the return value from the *Async method - the true vs false indicates whether it completed synchronously or not; if it completes synchronously, it will not invoke your callback - it is expected that you will invoke any required code.

As for the question: use the args in the event. The main reason for this is efficiency; the first example uses a "captured variable", which means it needs a capture context instance and a delegate instance per subscription. The second example does not use a captured variable, and as such the compiler optimizes the delegate creation to use a single static event handler instance for all subscriptions.

answered Dec 05 '19 at 14:32

Marc Gravell

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makes sense. But in theory the result should be the same either way, right? – Josh Dec 05 '19 at 14:43
1

yes, same result, but the non-capture version is more effiicent – Marc Gravell Dec 05 '19 at 14:46
Thanks! Do you know if the SocketAsyncEventArgs from the Completed event is the same object like the call parameter? I'm wondering about cleanup and stuff. When do I need to dispose the SocketAsyncEventArgs? – Josh Dec 05 '19 at 16:35
1

@Josh yes, it is the same instance – Marc Gravell Dec 05 '19 at 16:46

C# SocketAsyncEventHandler evaluate operation on Complete

1 Answers1