怎么回事？(200分)

这是为什么？
procedure TepCustomComboBox.CNDrawItem(var Message: TWMDrawItem);
var
State: TOwnerDrawState;
begin
with Message.DrawItemStruct^ do
begin
State := TOwnerDrawState(WordRec(LongRec(itemState).Lo).Lo);(编译时此句出错)
.......
end;
end;
出错提示：[Error] BoxCtrls.pas(635): Invalid typecast

注意： SizeOf(TOwnerDrawState) is 2! Byte is 1.
State:=TOwnerDrawState(Word(WordRec(LongRec(i).Lo).Lo));
or just use: State:=TOwnerDrawState(LongRec(i).Lo);

Done!