i want to swap the data one position to another position in excl..............i want to 6 th position quantyalloc and 7 th position ext$....this my code

i want to swap the data one position to another position in excl..............i want to 6 th position quantyalloc and 7 th position ext$....this my code
 private void SetHeaderName()     {         datagrid = ViewState["dt"] as DataTable;         datagrid.Columns.Remove("CompanywithCode");         datagrid.Columns.Add("dated1", typeof(string));         datagrid.Columns.Add("dated", typeof(string));         datagrid.Columns.Add("Diff", typeof(string));         datagrid.Columns.Add("ext", typeof(string));  datagrid.Columns.Remove("Shipdate");         datagrid.Columns.Remove("CDM_P ...