In order to avoid naming collisions in C# you can use a namespace- or class alias.
When making a new instance of the ArrayList class you would usually write:
using System.Collections; ... ArrayList data = new ArrayList();
However, if you already have another namespace imported with an ArrayList class you would get a naming conflict. To solve this you can add a namespace alias:
using Lists = System.Collections; ... Lists.ArrayList data = new Lists.ArrayList();
You could also have a class alias like this:
using List = System.Collections.ArrayList; ... List data = new List();