writefile返回值为ERROR_IO_PENDING，一直等待阻塞,不会继续运行下去

[huan7050]

小弟刚接触串口编程，在writefile的时候出现了问题，代码如下

BOOL CUSBDlg::SendData()
{
	BOOL Result;
	UINT LastError;
	UINT i;
	CString Str,str_send;
	DWORD Length = 0;

	if(MyDevFind==FALSE)
	{
        AddToInfoOut(_T("设备未找到"));
		return FALSE;
	}

	if(hWriteHandle==INVALID_HANDLE_VALUE)
	{
		AddToInfoOut(_T("无效的写报告句柄，可能是打开设备时失败"));
		return FALSE;
	}

	if(DataSending==TRUE)
	{
		AddToInfoOut(_T("数据正在发送中，暂时不能发送"));
		return FALSE;
	}

	WriteReportBuffer[0]=0x00; 
    
	CString str_id=itos(WriteReportBuffer[0],16).Right(2);
	GetDlgItem(IDC_EDIT_REPORTID)->SetWindowText(str_id);
	memset(WriteReportBuffer, 0, 512);
	
	GetDlgItemText(IDC_ESend, str_send);
	UINT count=str_send.GetLength();
    for(i=1; i<1+count; i++)
    {
      WriteReportBuffer[i]=(UCHAR)str_send.GetAt(i-1);
    }
    WriteReportBuffer[1] = 0x40;
	WriteReportBuffer[2] = 0xa2;
	WriteReportBuffer[3] = 0x02;
	
	AddToInfoOut(_T("发送信息：1字节报告ID+8字节实际数据"));
	Str=_T("");
	for(i=0; i<Capabilities.OutputReportByteLength; i++)
	{
		Str+=itos(WriteReportBuffer[i],16).Right(2)+_T(" ");
	}
	AddToInfoOut(Str, FALSE);

	str_send.Insert(0, _T("发送信息"));
	GetDlgItem(IDC_REC_STR)->SetWindowText(str_send);
	UpdateWindow();

	 DataSending=TRUE;

	Result=WriteFile(hWriteHandle,
			         &WriteReportBuffer, 
					 Capabilities.OutputReportByteLength,
					 &Length,
					&WriteOverlapped);

	if(Result==FALSE)
	{
		LastError=GetLastError();
		if((LastError==ERROR_IO_PENDING)||(LastError==ERROR_SUCCESS))
		{
			WaitForSingleObject(WriteOverlapped.hEvent, INFINITE);
			return TRUE;
		}
		else
		{
			DataSending=FALSE;
			AddToInfoOut(_T("发送失败，错误代码：")+itos(LastError));
			if(LastError==1)
			{
				AddToInfoOut(_T("该设备不支持WriteFile函数。"), FALSE);
			}
			return FALSE;
		}
	}

	AddToInfoOut(_T("数据发送成功！"));
	DataSending = FALSE;
	return TRUE;

}