Convert string to datatime format

1.

string str = "24/10/2008";
 DateTime dt = DateTime.ParseExact(str, "dd/MM/yyyy", 
                                   Thread.CurrentThread.CurrentCulture);
 
2. 
DateTime date = System.DateTime.ParseExact(str, "dd/MM/yyyy", null);
 DateTime date = System.DateTime.ParseExact(str, "HH:mm:ss", null);