DataTable dataTable = new DataTable();
dataTable.Columns.Add(new DataColumn("ID", typeof(int)));
dataTable.Columns.Add(new DataColumn("Name", typeof(string)));
dataTable.Rows.Add(1, "Mike");
dataTable.Rows.Add(2, "Cris");
dataTable.Rows.Add(3, "Ann");
var _selector = dataTable.Rows.Cast<DataRow>().Select(x => x.Field<int>("ID")).ToList();
ArrayList list = new ArrayList(_selector);