Query does not trigger Throw

[gwboolean]

I am having a little (lot) of trouble understanding what is going on here. I read the code below as this. If no record is yielded by the query call below, then the Trow CaseError should be executed. It is not.

                    If String.IsNullOrEmpty(LnkChangeRequestTableAdapter.FillByChangeManager(_MasterBase4_0ItemMasterDataSet.lnkChangeRequest, glbstrName).ToString) Then
                        Throw CaseError
                    End If

I have almost identical code in another form class that carries out this action exactly as desired.

            If String.IsNullOrEmpty(TblEmployeeTableAdapter.FillByLogin(_MasterBase4_0ItemMasterDataSet.tblEmployee, _strLoginName, _strPassword).ToString) Then
                Throw LoginError
            Else

So what is going south on me or what am I doing wroing?