Why is List not IEnumerable?

Question

[Edit: My apologies ... the original question wording was ambiguous and I was not getting the responses I am looking for]

For any class X that inherits from class Y,

Answer 1

I think I can see what you are getting at

bool IsCollectionOfValueTypes(Object argValue)
{
  Type t = argValue.GetType();
  if(t.IsArray)
  {
    return t.GetElementType().IsValueType;
  }
  else
  {
    if (t.IsGeneric)
    {
      Types[] gt = t.GetGenericArguments();
       return (gt.Length == 1) && gt[0].IsValueType;
    }
  }
  return false;
}

A start anyway might get a bit more complicated if you pass in a multidimensional array or a contructed type. It's all in the class somewhere though.