Set DragMode property to dmAutomatic.
procedure TForm1.EditTypeDragOver(Sender, Source : TObject;
X, Y : integer; State: TDragState; var Accept: Boolean);
begin
Accept:=true;
end;
procedure TForm1.EditTypeDragDrop(Sender, Source:TObject;
x,y:integer);
begin
(Sender as TEdit).Text:=(Source as TListBox).Items[(Source as TListBox).ItemIndex];
end;