In the strategy pattern, what's the best way to deal with shared behaviour?

Question

I have implemented the strategy pattern - is there a smart way to deal with the duplication of function2() and function1() below?
The IBehaviour interface has other members that don't share functionality.

class Behaviour1: IBehaviour
{
    public void DoSomething()
    {
        Function1();
    }
    //other functions of IBehaviour
}

class Behaviour2 : IBehaviour
{

   public void DoSomething()
   { 
       Function2();
       Function1();
   }
   //other functions of IBehaviour
}

class Behaviour3 : IBehaviour
{
    public void DoSomething()
    {
        Function2();
    }
    //other functions of IBehaviour
}

I already have one class to deal with this behaviour. Then I realised that different situations require different behaviours, so in this main class, I create a Behaviour object at run-time. I am reluctant to create yet another class for Function1 and Function2, so I wondered if there is something that I am missing.

Answer 1

One of two easy options comes to mind:

1. Make Behavior3 inherit from Behavior2. I would only recommend this approach if you can establish a clear "IS A" relationship or this design approach could really give you problems later if things change with how Behavior2 works in relation to Behavior3.

2. Move Function2() into a helper class that Behavior2 and Behavior3 can use indepedently.