delphi - Why is this wrong -

delphi - Why is this wrong -

i have next code

procedure tfrmjsapplications.colmaintstylesgetcontentstyle( sender: tcxcustomgridtableview; arecord: tcxcustomgridrecord; aitem: tcxcustomgridtableitem; out astyle: tcxstyle); var acolumn: tcxcustomgridtableitem; avalue: variant; begin inherited; seek acolumn := sender.finditembyname('colapplication_doc'); avalue := arecord.values[acolumn.index]; if vartostr(avalue) <> '' colmaint.properties.buttons[0].caption := 'redigere' else colmaint.properties.buttons[0].caption := 'opret' except on e:exception logfile.error('f_jsapplications.colmaintstylesgetcontentstyle: ' + e.message); end;

running on column in cxgrid. reason can't figure out line

if vartostr(avalue) <> ''

makes function crash. know when avalue becomes null value far can figure out vartostr should homecoming '' in case

the avalue not null empty. seek utilize check like

if(findvardata(avalue)^.vtype in [varnull, varempty])then ...

instead. or

if varisempty(avalue) or varisnull(avalue)

delphi devexpress variant tcxgrid