javascript代码：
function doublecheck(){
    if (window.document.readystate != null &&
            window.document.readystate != 'complete')
    {
        alert("正在处理，请等待！");
        return false;
    }
    else
    {
        messageclear();
        return true;
    }
}
在c#代码中：
this.backbutton.attributes["onclick"]         = "return doublecheck()";

http://www.cnblogs.com/dahuzizyd/archive/2007/01/04/javascript_double_click.html