Triggering methods that change instance state on other objects using a Dictionary
This looks ok to me on first glance.

I can only suggest the use of an Enum to strongly type the events that you are registering.

This allows you to search the code base quickly and avoids any typo's you may make:

    private string instanceVar;
    private Dictionary&lt;string, Action&gt; eventHandlers;

    public TestObject(string newInstanceVar)
    {
        this.instanceVar = newInstanceVar;
        eventHandlers = new Dictionary&lt;Events, Action&gt;();
        eventHandlers.Add(Events.event0, PrintInstanceVar);
        eventHandlers.Add(Events.event1, InstanceVarToUpper);
        eventHandlers.Add(Events.event2, ChangeOwnInstanceVar);
    }

    public enum Events
    {
        event0,
        event1,
        event2
    }