Use Native WLAN API in managed code

I'm afraid I have to reopen my own topic again. Has anyone implemented these functions in managed code (C#)? I'm having trouble finding the right types needed to p/invoke the API functions in the right way. This is what I have so far:

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanOpenHandle(
[In] UInt32 dwClientVersion,
[In,Out] IntPtr pReserved,
[Out] outUInt32 pdwNegotiatedVersion,
[Out] outIntPtr phClientHandle);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanCloseHandle(
[In] IntPtr hClientHandle,
[In,Out] IntPtr pReserved);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanEnumInterfaces(
[In] IntPtr hClientHandle,
[In,Out] IntPtr pReserved,
[Out] outIntPtr ppInterfaceList);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanQueryInterface(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] WLAN_INTF_OPCODE opCode,
[In,Out] IntPtr pReserved,
[Out] outUInt32 pdwDataSize,
[Out] outIntPtr ppData,
[Out] outWLAN_OPCODE_VALUE_TYPE pWlanOpcodeValueType);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanSetInterface(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] WLAN_INTF_OPCODE opCode,
[In] uint dwDataSize,
[In] IntPtr pData,
[In,Out] IntPtr pReserved);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanScan(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] IntPtr pDot11Ssid,
[In] IntPtr pIeData,
[In,Out] IntPtr pReserved);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanGetAvailableNetworkList(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] uint dwFlags,
[In,Out] IntPtr pReserved,
[Out] outIntPtr ppAvailableNetworkList);

privatestaticuint WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_ADHOC_PROFILES = 0x00000001;
privatestaticuint WLAN_AVAILABLE_NETWORK_INCLUDE_ALL_MANUAL_HIDDEN_PROFILES = 0x00000002;

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanSetProfile(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] uint dwFlags,
[In] string strProfileXml,
[In] string strAllUserProfileSecurity,
[In] bool bOverwrite,
[In,Out] IntPtr pReserved,
[Out] outuint pdwReasonCode);

[DllImport("wlanapi.dll", SetLastError = true)]
privatestaticexternint WlanGetProfile(
[In] IntPtr hClientHandle,
[In] IntPtr pInterfaceGuid,
[In] string strProfileName,
[In] IntPtr pReserved,
[Out] outIntPtr pstrProfileXml,
[Out] outIntPtr pdwFlags,
[Out] outIntPtr pdwGrantedAccess);

Unfortunately I don't have a clue, but another problem ;-)

I'm also trying to access the native wifi api from C#. But I'm already failing at the WlanEnumInterfaces function. To be exact, the function returns ok, but I have trouble converting the pointer to the WLAN_INTERFACE_INFO_LIST structure, just like you had before... When I do something like this:

WLAN_INTERFACE_INFO_LIST interfaceList = new WLAN_INTERFACE_INFO_LIST();
IntPtr interfaceListPtr;
WlanEnumInterfaces(handle, IntPtr.Zero, out interfaceListPtr); // returns 0 = OK
interfaceList = (WLAN_INTERFACE_INFO_LIST) Marshal.PtrToStructure(interfaceListPtr, typeof(WLAN_INTERFACE_INFO_LIST));

I always get an AccessViolationException. I also tried with Marshal.Alloc...ating some memory for the pointer, still the same. Here's my C# definition of the structs:

[StructLayout(LayoutKind.Sequential)]
publicstructWLAN_INTERFACE_INFO
{
publicGuid InterfaceGuid;
[MarshalAs(UnmanagedType.LPWStr, SizeConst=256)]
publicstring strInterfaceDescription;
publicWLAN_INTERFACE_STATE isState;
}

[StructLayout(LayoutKind.Sequential)]
publicstructWLAN_INTERFACE_INFO_LIST
{
publicint dwNumberOfItems;
publicint dwIndex;
// maybe I need some MarshalAs description here?
publicWLAN_INTERFACE_INFO[] InterfaceInfo;
}

Funny thing is, if I change the last field from WLAN_INTERFACE_INFO[] to WLAN_INTERFACE_INFO, it works. As most computers only have one WLAN adapter anyway, this could be used as a workaround, but I really would like to get it right. So it seems there is some problem with the marshalling of the array, probably because the size is unknown. You mentioned you got it all working except for some other error, maybe you could post the code that works for you (the structs, the dllimports, how you create the struct from the pointer)?

Thanks in advance,
Patrick

After some more investigation I do think that a MarshalAs should be possible to solve this problem. There is a SizeParamIndex field which can be set in the MarshalAs attribute. In our case it should be set to 0, because the first parameter of the struct (dwNumberOfItems) tells us the size of the array.

But I'm still playing around with the UnmanagedType, because setting it to LPArray results in a runtime error: "Cannot marshal field 'InterfaceInfo' of type 'WLAN_INTERFACE_INFO_LIST': Invalid managed/unmanaged type combination (Arrays fields must be paired with ByValArray or SafeArray)."

Uh, hadn't read your last post. I thought about that too, and I also tried some combination of the unmanaged array types and parameters, but couldn't get it to work. My guess is that it isn't possible if the marshaller doesn't know the size of the array, but if you find a way I'd be glad to hear. Your solution with the constructor is probably fine for most uses, the only thing is, it relies on an exact number of bytes for the fields, so it probably is very platform-dependent. Shouldn't be to much of a problem though, as these APIs are very platform-dependent, too.

Ok, your're right, it does have a maximum size, but I doubt that that is the size for all of the elements (although it could be). The main reason for this is the DOT11_PHY_TYPE array, with the ulong (64-bit!) uNumberOfPhyTypes variable counting the elements. Of course this array is maxed to WLAN_MAX_PHY_TYPE_NUMBER, but I have no idea what this usually is since I don't have the Wlanapi.h file. But I also tried reading the memory after the first WLAN_AVAILABLE_NETWORK struct bytewise searching for the SSID of the second network, which should be at the beginning of the next struct, and i can't find it (yes I considered it is in unicode). So it seems either the struct is somewhere completely else in memory or the other networks are not returned, which would be strange as the dwNumberOfItems in the WLAN_AVAILABLE_NETWORK_LIST is about right.

I'm really beginning to get frustrated, I just want to get the available networks and connect to one (at first). I've tried every approach from NDIS over WMI and WZC to the Native Wifi API, and nothing seems to work as it should. Well, maybe it's just me not getting it right... Unfortunately there don't seem to be working code samples around, too...

FYI, I use the Native Wifi LAN API for XP SP2.

Patrick

I finally found the solution for my first problem: it turns out that you don't pass in the interfaceGuid as an IntPtr but as a 'ref Guid'. This makes the WlanSetProfile function working as it should do.

But the WlanGetAvailableNetworkList still baffles me. I see exactly the same things as you do, Patrick. The number of items seems correct, but when I then look down the line I can't see all the SSIDs it has found.

Was anyone able to create a working C# wrapper for the native wireless api?

I followed the code on this thread but was unable to make it function as expected.

Thanks!