Accessing a Devices Interface/Class GUID always causes an error - c++

Question

Please see Edit below.
I am attempting to get the class/interface GUID of a connected device such as a TV or projector. I am using the function RegisterDeviceNotification() to give me the GUID when a TV is connected.
My Problem: When the TV is connected I can successfully be notified but when I go to access the GUID of the device(by inspecting the lParam structure) I get an access violation or error.
I cant figure out whats going wrong? Whenever I go to access or use the GUID my program fails, note my program doesn't crash but the output window writes something like First-chance exception at 0x001c1a9d in myProgram.exe... and I cant figure out whats going wrong?
HDEVNOTIFY *hDeviceNotify;
GUID interfaceClassGuid = { 0x25dbce51, 0x6c8f, 0x4a72, 0x8a,0x6d,0xb5,0x4c,0x2b,0x4f,0xc8,0x35 };
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
int wmId, wmEvent;
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_CREATE:
{
openConsoleWindow();
DEV_BROADCAST_DEVICEINTERFACE NotificationFilter;
ZeroMemory( &NotificationFilter, sizeof(NotificationFilter) );
NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
NotificationFilter.dbcc_classguid = interfaceClassGuid;
*hDeviceNotify = RegisterDeviceNotification( hWnd, &NotificationFilter, DEVICE_NOTIFY_WINDOW_HANDLE );
if (*hDeviceNotify == NULL)
printf("hDeviceNotify = NULL \n");
}
break;
case WM_DEVICECHANGE:
{
PDEV_BROADCAST_DEVICEINTERFACE b = (PDEV_BROADCAST_DEVICEINTERFACE) lParam;
// The following printf NEVER prints out.
// When accessing the below GUID I get an error:
// "First-chance exception at 0x001c1a9d in myProgram.exe: 0xC0000005: Access violation writing location 0x00000000."
printf("GUID: Data1: %x, Data2: %x, Data3: %x, Data4: %s \n", b->dbcc_classguid.Data1,
b->dbcc_classguid.Data2, b->dbcc_classguid.Data3, (char*)b->dbcc_classguid.Data4);
// The following function ALWAYS fails.
// GetLastError() gives the error "The parameter is incorrect"
HDEVINFO hDevInfo = SetupDiGetClassDevs(&b->dbcc_classguid, NULL, NULL, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
if (hDevInfo == INVALID_HANDLE_VALUE) {
//printf("hDevInfo == INVALID_HANDLE_VALUE \n");
outputLastError(_T("hDevInfo == INVALID_HANDLE_VALUE \n"));
}
}
break;
...
Edit: I've applied Hans' advice but still the same issue occurs(printf() never prints and the exception occurs):
case WM_DEVICECHANGE:
{
if (wParam != DBT_DEVNODES_CHANGED) {
printf("1: \n");
break;
}
PDEV_BROADCAST_HDR h = (PDEV_BROADCAST_HDR) lParam;
if (h->dbch_devicetype != DBT_DEVTYP_DEVICEINTERFACE) {
printf("2\n");
break;
}
PDEV_BROADCAST_DEVICEINTERFACE b = (PDEV_BROADCAST_DEVICEINTERFACE) h;
// When accessing the below GUID I get an error:
// "First-chance exception at 0x001c1a9d in TEST GUID Error.exe: 0xC0000005: Access violation writing location 0x00000000."
printf("GUID: Data1: %x, Data2: %x, Data3: %x, Data4: %s \n", b->dbcc_classguid.Data1,
b->dbcc_classguid.Data2, b->dbcc_classguid.Data3, (char*)b->dbcc_classguid.Data4);
// The following function ALWAYS fails.
// GetLastError() gives the error "The parameter is incorrect"
HDEVINFO hDevInfo = SetupDiGetClassDevs(&b->dbcc_classguid, NULL, NULL, DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
if (hDevInfo == INVALID_HANDLE_VALUE) {
//printf("hDevInfo == INVALID_HANDLE_VALUE \n");
outputLastError(_T("hDevInfo == INVALID_HANDLE_VALUE \n"));
}
}
break;