[CLOSED] set window's title problem

[hdsoso]

there is a window on a page, when set its'title from code behind

w_add.Title = "修改文章";

then , set its's title from js

var showAddWindow = function() {
            App.w_add.title = '新增文章'; 
            App.w_add.show();
        };

but the window's title dose not change. why?