visual C++更改屏幕方向问题--DEVMODE dmDisplayOrientation DMDO_90未定义

我似乎无法编译一些C++代码。我正在翻转显示器的方向，但VS2008告诉我DMDO_90和DMDO_270未识别：

error C2065: 'DMDO_90' : undeclared identifier
error C2065: 'DMDO_270' : undeclared identifier

我是不是错过了什么——包括什么？根据MSDN DEVMODE结构，应该定义DMDO（在dmDisplayOrientation部分下）--
这是我的代码：

#include <iostream>
#include <string>
#include <windows.h>
using namespace std;
DISPLAY_DEVICE GetPrimaryDevice()
{
    int index=0;
    DISPLAY_DEVICE dd;
    dd.cb = sizeof(DISPLAY_DEVICE);
    while (EnumDisplayDevices(NULL, index++, &dd, 0))
    {
        if (dd.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE) return dd;
    }
    return dd;
}
BOOL SetDisplayResolution(long degrees)
{
    DISPLAY_DEVICE dd = GetPrimaryDevice();
    DEVMODE dm;
    ZeroMemory(&dm, sizeof(dm));
    dm.dmSize = sizeof(DEVMODE);
    if (!EnumDisplaySettings(dd.DeviceName, ENUM_CURRENT_SETTINGS, &dm))
    {
        printf("EnumDisplaySettings failed:%dn", GetLastError());
        return FALSE;
    }
    switch(degrees)
    {
    case 90:
        dm.dmDisplayOrientation = DMDO_90; //error C2065: 'DMDO_90' : undeclared identifier
        break;
    case 270:
        dm.dmDisplayOrientation = DMDO_270; //error C2065: 'DMDO_90' : undeclared identifier
        break;
    default:
        break;
    }
    DWORD dwTemp = dm.dmPelsHeight;
    dm.dmPelsHeight = dm.dmPelsWidth;
    dm.dmPelsWidth = dwTemp;
    dm.dmFields = (DM_PELSWIDTH | DM_PELSHEIGHT);
    if (ChangeDisplaySettings(&dm, CDS_TEST) !=DISP_CHANGE_SUCCESSFUL)
    {
        printf("nIllegal graphics mode: %dn", GetLastError());
        return FALSE;
    }
    return (ChangeDisplaySettings(&dm, 0)==DISP_CHANGE_SUCCESSFUL);
}
int main()
{
    if (SetDisplayResolution(90))
    { 
        return true;
    }
    else
    {
        return false;
    }
}