Get last index of character in a string SQL server

Below SQL Function returns position of last occurrence or last index in a string of specified sub string

CREATE FUNCTION [dbo].[LastIndexOf] (

      @Chars VARCHAR(10),

      @String VARCHAR(MAX)

)

RETURNS INT

AS

BEGIN

      IF CHARINDEX(@Chars, @String) = 0

            RETURN 0

      ELSE

            RETURN 2 + DATALENGTH(@String) - CHARINDEX(REVERSE(@Chars), REVERSE(@String)) - DATALENGTH(@Chars)

      RETURN 0

END

Example:

SELECT dbo.LastIndexOf('A','AoneATwoAThree')

Output: 9