System.Windows.Forms.ListView.OnRetrieveVirtualItem C# (CSharp) Method

		protected virtual void OnRetrieveVirtualItem (RetrieveVirtualItemEventArgs e)
		{
			RetrieveVirtualItemEventHandler eh = (RetrieveVirtualItemEventHandler)Events [RetrieveVirtualItemEvent];
			if (eh != null)
				eh (this, e);
		}

            public ListViewItem this[int displayIndex]
            {
                get
                {
                    owner.ApplyUpdateCachedItems();

                    if (owner.VirtualMode)
                    {
                        // if we are showing virtual items, we need to get the item from the user
                        RetrieveVirtualItemEventArgs rVI = new RetrieveVirtualItemEventArgs(displayIndex);
                        owner.OnRetrieveVirtualItem(rVI);
                        rVI.Item.SetItemIndex(owner, displayIndex);
                        return(rVI.Item);
                    }
                    else
                    {
                        if (displayIndex < 0 || displayIndex >= owner.itemCount)
                        {
                            throw new ArgumentOutOfRangeException(nameof(displayIndex), displayIndex, string.Format(SR.InvalidArgument, nameof(displayIndex), displayIndex));
                        }

                        if (owner.IsHandleCreated && !owner.ListViewHandleDestroyed)
                        {
                            return((ListViewItem)owner.listItemsTable[DisplayIndexToID(displayIndex)]);
                        }
                        else
                        {
                            Debug.Assert(owner.listItemsArray is not null, "listItemsArray is null, but the handle isn't created");
                            return((ListViewItem)owner.listItemsArray[displayIndex]);
                        }
                    }
                }
                set
                {
                    owner.ApplyUpdateCachedItems();
                    if (owner.VirtualMode)
                    {
                        throw new InvalidOperationException(SR.ListViewCantModifyTheItemCollInAVirtualListView);
                    }

                    if (displayIndex < 0 || displayIndex >= owner.itemCount)
                    {
                        throw new ArgumentOutOfRangeException(nameof(displayIndex), displayIndex, string.Format(SR.InvalidArgument, nameof(displayIndex), displayIndex));
                    }

                    if (owner.ExpectingMouseUp)
                    {
                        owner.ItemCollectionChangedInMouseDown = true;
                    }

                    RemoveAt(displayIndex);
                    Insert(displayIndex, value);
                }
            }