Inserts an array of items into the LeadCollection at the specified index.
index
The 0-based index at which items should be inserted.
items
An array of items to insert. Items may be null.
InsertItemRange is meant to be overridden in a derived class. For a public method to insert items into the LeadCollection, see InsertRange.
LeadCollection accepts null as a valid value and allows duplicate items.
If index is equal to Count, items are added to the end of the LeadCollection.
This method raises the CollectionChanged event with the Add action.