var for db data

.NET 3.5, C#, web-application
Hi
I need a variable to store the data which was generated by a sql "select . . ." statement.
Currently I think, that an ArrayList-variable does this job correctly.
Since the data from the database is retrieved in a class.cs file, I need to pass this ArrayList as a parameter.
How do I pass an ArrayList as a parameter, in a way, that the ArrayList holds all items after return?
The second approach I am thining about, is to define a global ArrayList like
public static ArrayList DataArray = new ArrayList();
...