.net web use & backgroundworker threads

i'm perplexing async things webservice method. let contend i have following api call:

and slight called getproducts().

i getproducts methods, i things (eg. information database) following only before i relapse result, i wish async things (eg. send me an email).

so i did.

[webmethod(description = "bal blah blah.")]
public ilist<product> getproducts()
{
    // blah blah blah ..
    // information db .. hi db!
    // var mydata = .......
    // moar clbuttic blahs :)  (yes, google clbuttic don't know is)

    // ok .. send me an email sole reason, nonetheless infer async things works.
    var myobject = new myobject();
    myobject.senddataasync();

    // ok, relapse result.
    relapse mydata;
    }
}

public category trackingcode
{
    open vacant senddataasync()
    {
        var backgroundworker = new backgroundworker();
        backgroundworker.dowork += backgroundworker_dowork;
        backgroundworker.runworkerasync();
        //system.threading.thread.sleep(1000 * 20);
    }

    private vacant backgroundworker_dowork(object sender, doworkeventargs e)
    {
        sendemail();
    }
}

now, i run formula email never sent. i uncomment out thread.sleep .. following email sent.

so ... since credentials workman thread ripped down? dependant progenitor thread? wrong proceed i should doing credentials separate threading, asp.net web apps?