Paul,

I would return a XML string. From your example:

  FUNCTION AddTicketItem(nTransNum as Integer,;
                         cProductID as String) as Object;


*
* Return Value - Return the Item number assigned, and the price calculated
*
    local lcReturn as string 
    m.lcReturn = "" 

    select item_nbr, ;
       price ;
       from tabledt1 ;
       where [your condition] ;
       into cursor curitem nofilter

    if used('curitem') and ;
       reccount('curitem')>0 ;
    then 
        CURSORTOXML("curItem","lcReturn",1,32,0,"1")=0 ;
    endif 

    RETURN lcReturn
  ENDFUNC

Then, in your service client which is the c# app, you can create dataset from that XML string.

DataSet yourdataset = new DatSet();
string sReturnedFromSebService = yourservice.AddTicketItem(nTransNum,sProductID);
yourdataset.ReadXml(new StringReader(sReturnedFromSebService),XmlReadMode.Auto);

HTH