How to create an internal table with header line in smartforms

Hello Guys,

I need to append the data in my internal table in smartforms by the problem is an error occurred "a table without header line and therefore no component called tdline"

i already declared the data under types declaration tab

types : begin of ts_tline,

TDFORMAT type tdformat,

tdline type tdline,

end of ts_tline.

types : it_tline type table of ts_tline.

and declare these in global data

WA_TLINE type TS_TLINE

XT_TLINE type IT_TLINE

my syntax in program lines :

LOOP AT gy_lines INTO WA_PROJ.

SPLIT wa_proj AT cl_abap_char_utilities=>cr_lf

INTO table IT_SPLIT.

LOOP AT IT_SPLIT.

MOVE it_split-commentext TO xt_TLINE-tdline.

• an error occured at this part ****

append xt_TLINE.

ENDLOOP.

ENDLOOP.

what is wrong with my code..it cannot append data to xt_tline.

Please help.Will reward points

Thanks in advance

aVaDuDz