重新申明SendMessage
function Sendmessage(handle:hwnd;Wmsg:integer; Lparam:integer; Wparam:Pchar):integer;stdcall;external 'user32.dll' name 'SendMessageA';
var
PwdStr:String;
begin
SendMessage(Edit1.Handle,WM_GETTEXT,length(PwdStr)+1,PChar(PwdStr));
end;