First off, do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead.
Second, there are a number of ways to access the content of a List<T> - the simplest of which is to use the index:
obj o0 = myList;
obj o1 = myList;
There is also the Find method
] and no end of Linq methods you could use.
Sorry to be a bit vague, but your question is very vague as well!