public void SignIn(string userAtHost, string domainAndUsername, string password)
{
Lync.SignedIn += Lync_SignedIn;
Lync.SignInFailed += Lync_SignInFailed;
Lync.CallAccepted += Lync_CallAccepted;
Lync.VideoAvailabilityChanged += Lync_VideoAvailabilityChanged;
Lync.CallEnded += Lync_CallEnded;
Lync.CallDeclined += Lync_CallDeclined;
Lync.Initialize();
Lync.SignIn(userAtHost, domainAndUsername, password);
}