Avoid using the System.Collections namespace.
It is good practice to avoid the use of variables of type object*. By using object as a data type, you will not have compile time validation on your types, and you have to cast you objects every time you use them. Its the exact same situation when using the System.Collections namespace. Objects handled by System.Collections will only be validated to the object type at compile time. It compares to creating an object array to contain strings. You would never do that. You would create a string array.
The System.Collections namespace has served us well in the past, but now it is time to move on.
Use System.Collections.Generics instead!
*(sorry for the casing, but I think I have already written about my opinion about diverting the .Net languages so that the same classes are called different things in different languages)