转自 http://blog.csdn.net/itoccupant/article/details/32334877
最近从师兄手上接了一个C#的项目，需要用到MDI窗体，可是每当我显示子窗体的时候会有一次“闪烁”，很明显，看起来非常不爽，查找许久，知道是每次在show()子窗体的时候都会调用子窗体构造函数重绘窗体，其中需要将子窗体的尺寸调整到我在程序中设置的大小，无论我这样设置，这个窗口大小变化总会在show()的时候显示出来，我试过网上说的设置双缓冲、先隐藏窗体等启动之后再显示、借助定时器设置窗体的opacity属性，可是问题依旧，没有任何变化，一个偶然的机会找到了微软的MSDN论坛，发现遇到这个问题的哥们儿还不少，各种国家的程序员都有，其中一个哥们提供了一种一劳永逸的解法，彻底的解决了我的问题，天降救世主啊，为了这个问题我茶饭不思了好多天，现将方法分享一下，网上有很多人都有遇到这个问题，可是这是我唯一看到的解法，值得各位码农收藏啊，原文网址如下，谢谢这位美国小伙子：
http://social.msdn.microsoft.com/forums/en-US/winforms/thread/aaed00ce-4bc9-424e-8c05-c30213171c2c/
解决办法很easy：
将以下代码块加在父窗体中的任意位置
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x02000000;
return cp;
}
}
原理很简单，引用以下原话：
A form that has a lot of controls takes a long time to paint. Especially the Button control in its default style is expensive. Once you get over 50 controls, it starts getting noticeable. The Form class paints its background first and leaves "holes" where the controls need to Go. Those holes are usually white, black when you use the Opacity or TransparencyKey property. Then each control gets painted, filling in the holes. The visual effect is ugly and there's no ready solution for it in Windows Forms. Double-buffering can't solve it as it only works for a single control, not a composite set of controls.
I discovered a new Windows style in the SDK header files, available for Windows XP and (presumably) Vista: WS_EX_COMPOSITED. With that style turned on for your form, Windows XP does double-buffering on the form and all its child controls.