Asynchronous Call on ASP.NET (Simple question!!)

Hi... I always used synchronous calls for everything in asp.net, but that's because i don't understand what happens if in a request i make a asynchronous call (ie: to a web service) and it takes 10secs to return something.... the response will be not send until all finish???....

Pseudo code example:

PHP Code:

---

OnLoadFunction ()
{
         Response.Write ("Before Async Call")
         myWebService.AsyncDelay ( 10 )             // It takes 10 secs....
         Response.Write ("After Async Call")

         // ALL THE RESPONSE FINISH HERE (EXCEPT AsyncCallbackFunction ())
         //[B] NO OTHER METHOD NEEDS TO BE PROCESSED[/B]
}

AsyncCallbackFunction ()
{
         Response.Write ("10 secs later....")
} 


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The Response to the client would be: ????

PHP Code:

---

Before Async Call
After Async Call
10 secs later.... 


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or the AsyncCallbackFunction() method will be excecuted after the response finish.... Then the Response would be:

PHP Code:

---

Before Async Call
After Async Call 


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Thanks,
Diego