Overrideing variables

Question

Hello,
I'm trying to figure out how to override variables spawned in a derived class that are declared in a base class.

For instance:

public class construct
{

   public bool DENSITY = false;

}
public class mob : construct
{
  DENSITY = true;
}

Is this possible with some sort of modifier or something, or do I have to change DENSITY in a method/function/procedure/sub-routine (what name do C# programmers use?) in the derived class?