Where best to instantiate and close a Silverlight-enabled WCF Service from the Silverlight app?

...
{
    App.Client.MyOperationCompleted += Client_MyOperationCompleted;
    App.Client.MyOperationAsync(...);
}

void Client_MyOperationCompleted(object sender, MyOperationCompletedEventArgs e)
{
    App.Client.MyOperationCompleted -= Client_MyOperationCompleted;
}