帮我看一下这段代码哪错了，adoconn.Openschema(..)取得所有非系统表，

procedure TForm1.InitPnCombo();
var
 strTablename,strTabletype:AnsiString;
     tblTableNameSet:TADODataSet;
     redir:OleVariant;
     si:TSchemaInfo;
begin
  si:=siTables;
//  dm1.adoConn.GetTableNames(dbCmbTn.Items,true);
dm1.adoConn.OpenSchema(si,redir,null,tblTableNameSet);//这儿出错
tblTableNameSet.First();
while not tblTableNameSet.Eof do
begin
strTabletype:=tblTableNameSet.FieldValues['table_type'].bstrVal; if strTabletype='TABLE' then
begin
strTablename:=tblTableNameSet.FieldValues['table_name'].bstrVal;
       dbCmbTn.Items.Add(strTablename);
end; tblTableNameSet.Next();
end;
tblTableNameSet.Close();
end;