Specified Cast is not Valid C#

private static void FIllGroupID(string connectionString)
        {
            string queryStringNoGroupID =
                "Use Items select * from table_items_shelves where Item_ID is Null or Item_ID = '';";

            SqlConnection connection = new SqlConnection(connectionString);
            connection.Open();
            SqlCommand CommandGetAllWithoutID = new SqlCommand(queryStringNoGroupID, connection);


            DataTable DataTableAllWithoutID = new DataTable();

            SqlDataAdapter adapterAllWithoutID = new SqlDataAdapter(CommandGetAllWithoutID);


            adapterAllWithoutID.Fill(DataTableAllWithoutID);


            //this code will get empty items
            List<DataRow> nullOrEmpty = DataTableAllWithoutID.AsEnumerable()
                .Where(x => x.Field<object>("Item_ID") == null)
                .ToList();
            //this creates a dictionary of valid items
            Dictionary<object, List<DataRow>> dict = DataTableAllWithoutID.AsEnumerable()
                .Where(x => x.Field<object>("Item_ID") != null)
                .GroupBy(x => x.Field<object>("Item_ID"), x => x)
                .ToDictionary(x => x.Key, x => (List<DataRow>)x.ToList());
            //create IEnumerator for the null items
            IEnumerator<DataRow> emptyRows = nullOrEmpty.GetEnumerator();
            emptyRows.MoveNext();
            Boolean noMoreEmptyRows = false;
            if (emptyRows != null)
            {
                foreach (object key in dict.Keys)
                {
                    Console.WriteLine(key.ToString());
                    //get count of items
                    int count = dict[key].Count;

//exception on this line

                    int itemID = (int)key;


                    for (int index = count; count < 8; count++)
                    {
                        //get an item from the null list
                        emptyRows.Current["Item_ID"] = itemID;
                        Console.WriteLine("current item ID "+itemID);
                        Console.ReadKey();
                        emptyRows.MoveNext();
                        if (emptyRows.Current == null)
                        {
                            noMoreEmptyRows = true;
                            break;
                        }
                    }
                    if (noMoreEmptyRows == true)
                    {
                        break;
                    }
                }
            }
            //now test if there are still items that contains empty items
            if (emptyRows.Current != null)
            {
                //add code to create new group
            }