TTreeView get the name of the root node

procedure TreeViewOnDoubleClick(Sender: TObject);
begin

     if TreeView.Selected.Data=0 then begin
         exit;
     end else
     begin

         IF TreeView.Selected.StateIndex=1 Then Begin
              //Some Code
         End Else
         Begin
              //Some Code
         End;

     end;
end;

procedure Form1_Button2_OnClick (Sender: TObject; var Cancel: boolean);
var
    treenode, treenode1, treenode2,treenode3 : TTreenode;
    sWorks : TDataSet;
    sHOUSE,sPOD,sST,sKV:String;
    sSQL:string;
begin
    Tree_Set;

    Treeview.Items.BeginUpdate;

    sSQL:='SELECT "дом."||HOUSE.dom||ifnull("-"||HOUSE.let,"")||ifnull(", корп."||HOUSE.korp,""), "под."||H_KV.pod, "ст."||H_KV.st, "кв."||H_KV.kv, HOUSE.segment, STREET.id, ';
    sSQL:=sSQL+'(HOUSE.id||STREET.street||ifnull("дом."||HOUSE.dom,"")||ifnull("под."||H_KV.pod,"")||ifnull("ст."||H_KV.st,"")||ifnull("кв."||H_KV.kv,"")) as full_dom, HOUSE.id, H_KV.id ';
    sSQL:=sSQL+'FROM STREET LEFT JOIN HOUSE ON HOUSE.id_STREET=STREET.id LEFT JOIN H_KV ON H_KV.id_HOUSE=HOUSE.id WHERE STREET.id="'+IntToStr(Form1.ComboBox1.dbItemID)+'" ';
    sSQL:=sSQL+'ORDER BY full_dom';

    sHOUSE:='';sPOD:='';sST:='';sKV:='';    

    SQLQuery(sSQL, sWorks);

    While not sWorks.EOF do Begin
            IF sWorks.Fields[4].AsString='Многоэтажный' Then Begin
                IF sHOUSE<>sWorks.Fields[0].AsString Then Begin
                    sHOUSE:=sWorks.Fields[0].AsString;
                    treenode := Treeview.Items.Add(nil,sWorks.Fields[0].AsString);
                end;
                IF sPOD<>sHOUSE+sWorks.Fields[1].AsString Then Begin
                    sPOD:=sHOUSE+sWorks.Fields[1].AsString;
                    treenode1 := Treeview.Items.AddChild(treenode,sWorks.fields[1].asstring);
                End;
                IF sST<> sHOUSE+sPOD+sWorks.Fields[2].AsString Then Begin
                    sST:=sHOUSE+sPOD+sWorks.Fields[2].AsString;
                    treenode2 := Treeview.Items.AddChild(treenode1,sWorks.Fields[2].AsString);
                End;
                IF sKV<>sHOUSE+sPOD+sST+sWorks.Fields[3].AsString Then Begin
                    sKV:=sHOUSE+sPOD+sST+sWorks.Fields[3].AsString;
                    treenode3 := Treeview.Items.AddChild(treenode2,sWorks.Fields[3].AsString);
                    treenode3.Data := sWorks.fields[8].AsInteger;
                    treenode3.StateIndex := 1;
                End;
            End else
            Begin
                IF sWorks.Fields[3].AsString>'' Then Begin
                    IF sHOUSE<>sWorks.Fields[6].AsString Then Begin
                        sHOUSE:=sWorks.Fields[6].AsString;
                        treenode := Treeview.Items.Add(nil,sWorks.Fields[0].AsString+', '+sWorks.Fields[3].AsString);
                        treenode.Data := sWorks.fields[8].AsInteger;
                        treenode.StateIndex := 1;
                    End;
                End else
                begin
                    IF sHOUSE<>sWorks.Fields[6].AsString Then Begin
                        sHOUSE:=sWorks.Fields[6].AsString;
                        treenode := Treeview.Items.Add(nil,sWorks.Fields[0].AsString);
                        treenode.Data := sWorks.fields[5].AsInteger;
                        treenode.StateIndex := 0;
                    End;
                end;
            end;
        sWorks.Next;
        End;
    sWorks.Free;
    Treeview.Items.EndUpdate;
end;