调用 WriteFile写数据时出错，用GetLastError得到错误代码为87（无效参数）。
代码片段如下：
if ((!WriteFile(
m_hDevEx,
pBuf,
size,
&WriteBytes,
&Overlapped)) &&
(GetLastError() != ERROR_IO_PENDING))
{
OutputDebugString("Write error\n");
return false;
}问题出在最后一个参数Overlapped，初始化是这样的：
OVERLAPPED Overlapped;
Overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);这种初始化在ReadFile时时没有问题的，而WriteFile时需要将该结构体中的Offset，OffsetHigh两个参数设置成零，即:
OVERLAPPED Overlapped;
Overlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
Overlapped.Offset = 0;
Overlapped.OffsetHigh = 0;
以上这样初始化之后，错误消失！
WriteFile操作时返回87错误,布布扣,bubuko.com
原文：http://blog.csdn.net/saloon_yuan/article/details/29569527