Declare a varied-length array of structures and use marshalling

[peary]

Hi, everyone,

I'm writing a program to discover wireless network
using Windows Native Wifi API & VB.net.
I have to declare the windows API in my VB.net program.
The original windows declaration is as below.

The problem is in "struct _WLAN_AVAILABLE _NETWORK_LIST",
it declared "WLAN_AVAILABLE _NETWORK Network[1];".
I think which means a Network[] array of struct WLAN_AVAILABLE_ NETWORK.
But how about the size of the Network[] array?
Is it "1" or more? what does "1" mean?
If I give it the size of 1, then I can get the first network back,
but if I give it more than 1, for example, 10,
then I got an error of "AccessViolatio nException".

The full message is "Service cannot be started. System.AccessVi olationExceptio n:
Attempted to read or write protected memory.
This is often an indication that other memory is corrupt."

Actually, the size of the Network[] array is decided by
dwNumberOfItems at run time, which means the size of the
Network[] array is varied-length not fixed, and in most situations
, the size should be more than 1.

I've searched the solution on the internet, and found some similar situations.
They said we should use IntPtr to get the address of the structure array and
then use Marshal class(Marshal.c opy(), Marshal.PtrToSt ructure()....) to get the array,
instead of declared it as a structure array, but they didn't post a sample Marshalling code.

I've tried to code, but still got "AccessViolatio nException" at Marshalling.
Anyone knows how to solve the problem?
Could you write a sample code for me in VB.net or C# without unsafe code?

Thanks so much. I appreciate your help.

Windows Native Wifi declarations:
'-----function-----
DWORD WINAPI WlanGetAvailabl eNetworkList(
HANDLE hClientHandle,
const GUID* pInterfaceGuid,
DWORD dwFlags,
PVOID pReserved,
PWLAN_AVAILABLE _NETWORK_LIST* ppAvailableNetw orkList
);

'-----structure-----
typedef struct _WLAN_AVAILABLE _NETWORK_LIST {
DWORD dwNumberOfItems ; '===>the actual size of array
DWORD dwIndex;
WLAN_AVAILABLE_ NETWORK Network[1]; '===>how to declare the array? should I give it fixed size of 1 or change it to an IntPtr
} WLAN_AVAILABLE_ NETWORK_LIST, *PWLAN_AVAILABL E_NETWORK_LIST;

typedef struct _WLAN_AVAILABLE _NETWORK {
WCHAR strProfileName[256];
DOT11_SSID dot11Ssid;
DOT11_BSS_TYPE dot11BssType;
ULONG uNumberOfBssids ;
BOOL bNetworkConnect able;
WLAN_REASON_COD E wlanNotConnecta bleReason;
ULONG uNumberOfPhyTyp es;
DOT11_PHY_TYPE dot11PhyTypes[8];
BOOL bMorePhyTypes;
WLAN_SIGNAL_QUA LITY wlanSignalQuali ty;
BOOL bSecurityEnable d;
DOT11_AUTH_ALGO RITHM dot11DefaultAut hAlgorithm;
DOT11_CIPHER_AL GORITHM dot11DefaultCip herAlgorithm;
DWORD dwFlags;
DWORD dwReserved;
} WLAN_AVAILABLE_ NETWORK, *PWLAN_AVAILABL E_NETWORK;

typedef struct _DOT11_SSID {
ULONG uSSIDLength;
UCHAR ucSSID[32];
} DOT11_SSID, *PDOT11_SSID;


'-----Enumeration-----
typedef enum _DOT11_BSS_TYPE
{
dot11_BSS_type_ infrastructure,
dot11_BSS_type_ independent,
dot11_BSS_type_ any
}DOT11_BSS_TYPE , *PDOT11_BSS_TYP E;

typedef DWORD WLAN_REASON_COD E, *PWLAN_REASON_C ODE;

typedef enum _DOT11_PHY_TYPE
{
dot11_phy_type_ unknown,
dot11_phy_type_ any,
dot11_phy_type_ fhss,
dot11_phy_type_ dsss,
dot11_phy_type_ irbaseband,
dot11_phy_type_ ofdm,
dot11_phy_type_ hrdsss,
dot11_phy_type_ erp,
dot11_phy_type_ IHV_start,
dot11_phy_type_ IHV_end
}DOT11_PHY_TYPE , *PDOT11_PHY_TYP E;

typedef enum _DOT11_AUTH_ALG ORITHM
{
DOT11_AUTH_ALGO _80211_OPEN,
DOT11_AUTH_ALGO _80211_SHARED_K EY,
DOT11_AUTH_ALGO _WPA,
DOT11_AUTH_ALGO _WPA_PSK,
DOT11_AUTH_ALGO _WPA_NONE,
DOT11_AUTH_ALGO _RSNA,
DOT11_AUTH_ALGO _RSNA_PSK,
DOT11_AUTH_ALGO _IHV_START,
DOT11_AUTH_ALGO _IHV_END
}DOT11_AUTH_ALG ORITHM, *PDOT11_AUTH_AL GORITHM;

typedef enum _DOT11_CIPHER_A LGORITHM
{
DOT11_CIPHER_AL GO_NONE,
DOT11_CIPHER_AL GO_WEP40,
DOT11_CIPHER_AL GO_TKIP,
DOT11_CIPHER_AL GO_CCMP,
DOT11_CIPHER_AL GO_WEP104,
DOT11_CIPHER_AL GO_WPA_USE_GROU P,
DOT11_CIPHER_AL GO_RSN_USE_GROU P,
DOT11_CIPHER_AL GO_WEP,
DOT11_CIPHER_AL GO_IHV_START,
DOT11_CIPHER_AL GO_IHV_END
}DOT11_CIPHER_A LGORITHM, *PDOT11_CIPHER_ ALGORITHM;

[Motoma]

You will probably need to know how many networks are available. If you go beyond that number, I'm sure you will get an exception thrown.
I don't know how you would go about getting this, but you may want to check google for something like "wifi network enumeration api" or something like that.