Change antenna of XR480 reader simultaneously in c#

Question

i am using XR480 RFID reader, in which i need to change antenna from 1 to 2, 2 to 3 .... in looping..

when i  use (each) single antenna it works properly, but when i try for looping it does'nt work.. can anybody help me ? plz

 

this is my code for connect antenna to reader

 

  byte SAAT_SCAN_TRIES = 3;       

 switch (SAAT_CODE_TYPE)        

         {               

 case 0://Read EPC Code 

return

 RfidApi.SAAT_6CReadEPCCode(pHandle, sAntenna1, (byte)SAAT_READ_TYPE, SAAT_SCAN_TRIES);        

 case 1://Read TID Code              

 return

 RfidApi.SAAT_6CReadTIDCode(pHandle, sAntenna1, (byte)SAAT_READ_TYPE, SAAT_SCAN_TRIES);              

 case 2://Read UID Code               

retur

 RfidApi.SAAT_6BReadUIDCode(pHandle, sAntenna1, (byte)SAAT_READ_TYPE);      

           }              

 return false;

and this is function

  [DllImport("RFIDAPI.dll", EntryPoint = "SAAT_6CReadEPCCode")]     
    [return: MarshalAs(UnmanagedType.I1)]     
    public static extern bool SAAT_6CReadEPCCode(IntPtr pHandle, byte nAntenna, byte nType,             byte nTagCount);