Problems using WlanGetNetworkBssList of the WLAN API

[NilsHoyer]

I have the following code, I believe I should be able to execute as well. But my App crashes, without a special error message or exception. So, I believe, it based on a memory violation, maybe based on a wrong struct or function definition in your code.

The problem occurs only, if I use the WlanGetNetworkBssList, if not, everything works like excepted.

Unfortunately, I don't have an idea, how I can offer better information to reproduce or hunt this issue 😥.

The networkInterface is a part of the result from NetworkInterface.GetAllNetworkInterfaces(), checked it's a WLAN interface.

My code:

static void ThrowException(Win32Error win32Error)
{
    if (win32Error != ERROR_SUCCESS)
        throw new Exception(win32Error.ToString());
}

ThrowException(WlanOpenHandle(2, 0, out var _, out var clientHandle));

ThrowException(WlanQueryInterface(
    clientHandle,
    Guid.Parse(networkInterface.Id),
    wlan_intf_opcode_current_connection,
    0,
    out var _,
    out var data,
    out var _));

var connectionAttributes = Marshal.PtrToStructure<WLAN_CONNECTION_ATTRIBUTES>(data);

if (WlanGetNetworkBssList(
    clientHandle,
    Guid.Parse(networkInterface.Id),
    connectionAttributes.wlanAssociationAttributes.dot11Ssid,
    connectionAttributes.wlanAssociationAttributes.dot11BssType,
    connectionAttributes.wlanSecurityAttributes.bSecurityEnabled,
    0,
    out var ppWlanBssList) == ERROR_SUCCESS)
{
    ...

    WlanFreeMemory(ppWlanBssList);
}

WlanFreeMemory(data);

ThrowException(WlanCloseHandle(clientHandle));

[dahall]

Working on this now, fix or resolution shortly.

FYI If you're using Vanara, both HRESULT and Win32Error have a ThrowIfFailed method you can use like

WlanOpenHandle(2, 0, out var _, out var clientHandle).ThrowIfFailed();

Win32Error provides some methods similar to your ThrowException for other return values (HANDLE, int, etc.) when methods use SetLastError to provide error codes.

[dahall]

I was able to get this working with the current code base using the following:

using var hWlan = WlanOpenHandle();
WlanQueryInterface(hWlan, PrimaryInterface, WLAN_INTF_OPCODE.wlan_intf_opcode_current_connection,
   default, out _, out SafeHWLANMEM? data, out _).ThrowIfFailed();
var connectionAttributes = data.DangerousGetHandle().ToStructure<WLAN_CONNECTION_ATTRIBUTES>();
WlanGetNetworkBssList(hWlan, PrimaryInterface, connectionAttributes.wlanAssociationAttributes.dot11Ssid,
   connectionAttributes.wlanAssociationAttributes.dot11BssType, connectionAttributes.wlanSecurityAttributes.bSecurityEnabled,
   default, out var mem).ThrowIfFailed();
var list = mem.DangerousGetHandle().ToStructure<WLAN_BSS_LIST>()!;
Console.Write(string.Join("\n", list.wlanBssEntries.Select(e => $"{e.uPhyId}\t{e.dot11Bssid}\t{e.dot11BssType}\t" +
   "{e.dot11BssPhyType}\tstr={e.lRssi}\tper={e.usBeaconPeriod}\tfrq={e.ulChCenterFrequency}\t{e.ulIeOffset}:{e.ulIeSize}")));

WlanCloseHandle and WlanFreeMemory are automatically called by the Safe handles.

[NilsHoyer]

Thanks a lot for your attention, work and suggestions!