public void ActivateTab(string tabName)
        {
            if (Tabnames[tabName])
            {
                return;
            }
            IsRunning = true;
            try
            {
                switch (tabName)
                {
                case "connectionTabItem":   { Tabnames[tabName] = CT.ActivateTab(); break; }

                case "tableTabItem":        { Tabnames[tabName] = TT.ActivateTab(); break; }

                case "documentTabItem":     { Tabnames[tabName] = DT.ActivateTab(Settings.CreateSchema()); break; }
                }
            }
            catch (Exception e)
            {
                SIEEMessageBox.Show(e.Message, "Error in " + tabName, MessageBoxImage.Error);
                DataLoaded  = false;
                SelectedTab = 0;
                TabNamesReset();
            }
            finally { IsRunning = false; }
        }