Opacity属性是你所需要的黯淡的一种形式。您需要在创建覆盖，我的code this螺纹展示了如何做到这一点。

The Opacity property is what you need to "dim" a form. You'll need to create an overlay, my code in this thread shows how to do this.

注意不要使它看起来像你的程序显示UAC提示。虽然可能在适当的浏览器，用户将不会有任何问题认识到通过一个对话框覆盖的窗口被禁​​止。控制涂料本身不同要想清楚。

Be careful to not make it look like your program is displaying a UAC prompt. While perhaps appropriate in browsers, the user will never have any trouble recognizing that a window overlaid by a dialog is disabled. Controls paint themselves differently to make it clear.