Command Pattern : How to pass parameters to a command?

You'll need to associate the parameters with the command object, either by constructor or setter injection (or equivalent). Perhaps something like this:

public class DeletePersonCommand: ICommand
{
     private Person personToDelete;
     public DeletePersonCommand(Person personToDelete)
     {
         this.personToDelete = personToDelete;
     }

     public void Execute()
     {
        doSomethingWith(personToDelete);
     }
}