SAP Function module - GUI_DOWNLOAD CC++C#Access

用这个function module 可以下载文件到本地，实现数据的local处理。
1。 首先，提两个相关的function module，涉及到参数CODEPAGE，影响文件的输出格式。
function module SCP_CODEPAGE_BY_EXTERNAL_NAME，可以转换输出文件格式，例，输入'UTF-8'，返回4110，输入'GBK',返回8400。
function module NLS_GET_FRONTEND_CP，输入语言，返回参数CODEPAGE的四位数字值，例:输入'ZH',返回1160这个四位阿拉伯数字。
平时我们所用的，只要输入这四个参数就可以使用了。

DATA : C_FULLPATH TYPE STRING.

例如，
CALL FUNCTION 'GUI_DOWNLOAD'
  EXPORTING
    BIN_FILESIZE = 255
    FILENAME     = C_FULLPATH
    FILETYPE     = 'BIN'
    APPEND       = ''
  IMPORTING
    FILELENGTH   = ''
  TABLES
    DATA_TAB     = ''.
 

CALL FUNCTION 'GUI_DOWNLOAD'
    EXPORTING
        BIN_FILESIZE              = 255
        FILENAME                  = C_FULLPATH
        FILETYPE                  = 'DAT'
        APPEND                    = ' '
        WRITE_FIELD_SEPARATOR     = 'X'
        HEADER                    = '00'
        TRUNC_TRAILING_BLANKS     = ' '
        WRITE_LF                  = 'X'
        COL_SELECT                = ' '
        COL_SELECT_MASK           = ' '
        DAT_MODE                  = ' '
        CONFIRM_OVERWRITE         = ' '
        NO_AUTH_CHECK             = ' '
        CODEPAGE                  = '4103'
        IGNORE_CERR               = ABAP_TRUE
        REPLACEMENT               = '#'
        WRITE_BOM                 = 'X'
        TRUNC_TRAILING_BLANKS_EOL = 'X'
        WK1_N_FORMAT              = ' '
        WK1_N_SIZE                = ' '
        WK1_T_FORMAT              = ' '
        WK1_T_SIZE                = ' '
        WRITE_LF_AFTER_LAST_LINE  = ABAP_TRUE
        SHOW_TRANSFER_STATUS      = ABAP_TRUE
   IMPORTING
        FILELENGTH                = TABLES
        DATA_TAB                  = IT_KNA1
        FIELDNAMES                = IT_FILEDNAME[]
   EXCEPTIONS
        FILE_WRITE_ERROR          = 1
        NO_BATCH                  = 2
        GUI_REFUSE_FILETRANSFER   = 3
        INVALID_TYPE              = 4
        NO_AUTHORITY              = 5
        UNKNOWN_ERROR             = 6
        HEADER_NOT_ALLOWED        = 7
        SEPARATOR_NOT_ALLOWED     = 8
        FILESIZE_NOT_ALLOWED      = 9
        HEADER_TOO_LONG           = 10
        DP_ERROR_CREATE           = 11
        DP_ERROR_SEND             = 12
        DP_ERROR_WRITE            = 13
        UNKNOWN_DP_ERROR          = 14
        ACCESS_DENIED             = 15
        DP_OUT_OF_MEMORY          = 16
        DISK_FULL                 = 17
        DP_TIMEOUT                = 18
        FILE_NOT_FOUND            = 19
        DATAPROVIDER_EXCEPTION    = 20
        CONTROL_FLUSH_ERROR       = 21
        OTHERS                    = 22.