问SetupDiEnumDeviceInterfaces失效问题

EN

#include <windows.h>
#include <setupapi.h>
#include <stdio.h>
#pragma comment(lib,"SetupAPI") 
//
int main() 
{
    // Set up handles and data storage
    HDEVINFO hDevInfo;
    // Load GUID Classes
    static GUID GUID_DEVINTERFACE_USB_HUB={ 0xf18a0e88, 0xc30c, 0x11d0, {0x88, 0x15, 0x00, 0xa0, 0xc9, 0x06, 0xbe, 0xd8} }; 
    static GUID GUID_DEVINTERFACE_USB_DEVICE ={ 0xA5DCBF10L, 0x6530, 0x11D2, { 0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED } }; 
    static GUID GUID_DEVINTERFACE_USB_HOST_CONTROLLER={ 0x3abf6f2d, 0x71c4, 0x462a, {0x8a, 0x92, 0x1e, 0x68, 0x61, 0xe6, 0xaf, 0x27}}; 
    // 
    SP_DEVICE_INTERFACE_DATA ifdata;
    // Create a HDEVINFO with all present devices.
    hDevInfo = SetupDiGetClassDevs(NULL,0, 0, DIGCF_PRESENT | DIGCF_ALLCLASSES | DIGCF_DEVICEINTERFACE);
    //
        if (INVALID_HANDLE_VALUE == hDevInfo)
        {
        return FALSE;
        }
        else
        {
        printf("Device info set handle for all devices attached to system: 0x%x\n", hDevInfo);
        }
    //
    BOOL bResult = TRUE;
    DWORD nCount = 0;
    //
        while (bResult)
        {
        //
            ifdata.cbSize=sizeof(ifdata);
            //  
            bResult = SetupDiEnumDeviceInterfaces(
            hDevInfo,  
            NULL,   
            &GUID_DEVINTERFACE_USB_DEVICE,   
            (ULONG)nCount,  
            &ifdata); 


        //
        if(!bResult)
            {       
            printf("Error Failed\n");       
            //fails here with error 6 invalid handle 
            }
        }



    // Cleanup
    SetupDiDestroyDeviceInfoList(hDevInfo);
    //
    system ("pause");
    //
    return 0;

}