Sort items and update OrderNo

Question

i have a table with list of unsorted items. I need to sort it ASC by Stext column and UPDATE `OrderNo" starting 1 If there are 4 rows, last OrderNo should be 4, if there is more then 5, etc...

SELECT [ID]
      ,[RefAg]
      ,[IDS]
      ,[SText]
      ,[OrderNo]
  FROM [Stw].[dbo].[List]
  where refAg = 22
  order by Stext ASC;

table sorted by previous query:

ID  |RefAg  | IDS                | SText                     | OrderNo
----|-------|--------------------|---------------------------|--------
1001|   22  | Item A             | Item A                    | 2
1128|   22  | Item B             | Item B                    | 4
986 |   22  | Item C             | Item C                    | 1
1122|   22  | Item D             | Item D                    | 3

need to update OrderNo like this:

ID  |RefAg  | IDS                | SText                     | OrderNo
----|-------|--------------------|---------------------------|--------
1001|   22  | Item A             | Item A                    | 1
1128|   22  | Item B             | Item B                    | 2
986 |   22  | Item C             | Item C                    | 3
1122|   22  | Item D             | Item D                    | 4