if (stars == 2 || stars ==6 || stars ==10)
{
    do something
}

if (stars == {2, 4, 6}) <--- MATLAB style
{
       do something
}

public static class GenericExtensions
{
    public static bool In<T>(this T @this, params T[] listOfItems)
    {
        if (null == listOfItems) return false;
        return listOfItems.Contains(@this);
    }
}

var items = new []{2,4,6};
if(items.IndexOf(stars) > -1)
{
  // do something
}

var items = new List<int>{2,4,6};
if(items.Contains(stars))
{
  // do something
}