Making Dataset with Two tables from two dataset

sqlStr = "select EventID as EventID,EventName as EventName from EventsAutoTweet";
Ds = objConAT.SelectDataset(sqlStr, "EventTable");
//Ds.Tables[0].TableName = "EventTable";
//SentenceDeli,ShortUrlDeli
sqlStr = "select * from StoryStructure";
DataSet Ds2 = objConAT.SelectDataset(sqlStr, "StoryStructure")
Ds.Tables.Add( Ds2.Tables[0].Copy());