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