int  IndexOf(
   CObject*  element      // pointer to the element
   )

//--- example for CList::IndexOf(CObject*)
#include <Arrays\List.mqh>
//---
void OnStart()
  {
   CList *list=new CList;
   //---
   if(list==NULL)
     {
      printf("Object create error");
      return;
     }
   CObject *object=new CObject;
   if(object==NULL)
     {
      printf("Element create error");
      delete list;
      return;
     }
   if(list.Add(object))
     {
      int pos=list.IndexOf(object);
     }
   //--- delete list
   delete list;
  }