Don't declare it as a var unless you absolutely have to - try declaring as the type that Peapoles returns. If Peapoles is returning the base class because it doesn't know they are derived instances, then cast the item to the inherited version and try that:
MyClass derived = item as MyClass;
if (derived != null)
{
...
}
You can only use properties of derived classes if the variable you are accessing them via is derived, not base class.