C# Signature:

        [DllImport("Wlanapi", EntryPoint = "WlanQueryInterface")]
        public static extern uint WlanQueryInterface([In] IntPtr hClientHandle,
        [In] ref Guid pInterfaceGuid,
        WLAN_INTF_OPCODE OpCode,
        IntPtr pReserved,
        [Out] out uint pdwDataSize,
        ref IntPtr ppData,
        IntPtr pWlanOpcodeValueType);

VB Signature:

     <DllImport("Wlanapi", EntryPoint := "WlanQueryInterface")> _
     Public Shared Function WlanQueryInterface(<[In]> ByVal hClientHandle As IntPtr, _
    <[In]> ByRef pInterfaceGuid As Guid, ByVal OpCode As WLAN_INTF_OPCODE, _
    ByVal pReserved As IntPtr, <Out> ByRef pdwDataSize As UInteger, _
    ByRef ppData As IntPtr, ByVal pWlanOpcodeValueType As IntPtr) As UInteger
     End Function

User-Defined Types:

WLAN_INTF_OPCODE

Alternative Managed API:

There is a managed WiFi API available on codeplex http://managedwifi.codeplex.com/

Notes:

Depending on the opcode, the data returned in the memory pointed to by ppData can be:

WLAN_RADIO_STATE

DOT11_BSS_TYPE

WLAN_INTERFACE_STATE

WLAN_CONNECTION_ATTRIBUTES

WLAN_AUTH_CIPHER_PAIR_LIST

WLAN_COUNTRY_OR_REGION_STRING_LIST

WLAN_STATISTICS

Tips & Tricks:

Please add some!

Sample Code:

C#

       IntPtr handle = IntPtr.Zero;
       uint negotiatedVersion;        
       try
       {    
        if (WlanOpenHandle(1, IntPtr.Zero, out negotiatedVersion, ref handle) != 0)
            return;

        IntPtr ptr = new IntPtr();
        if (WlanEnumInterfaces(handle, IntPtr.Zero, ref ptr) != 0)
            return;

        WLAN_INTERFACE_INFO_LIST infoList = new WLAN_INTERFACE_INFO_LIST(ptr);
        WlanFreeMemory(ptr);

        Guid guid;
        uint dataSize;
        WLAN_CONNECTION_ATTRIBUTES connection;
        // Call wlanqueryinterface for all the interfaces in the list
        for (int i = 0; i < infoList.dwNumberOfItems; i++)
        {
            guid = infoList.InterfaceInfo[i].InterfaceGuid;
            if (WlanQueryInterface(handle, ref guid, WLAN_INTF_OPCODE.wlan_intf_opcode_current_connection, IntPtr.Zero, out dataSize, ref ptr, IntPtr.Zero) != 0)
            return;

            connection = (WLAN_CONNECTION_ATTRIBUTES)Marshal.PtrToStructure(ptr, typeof(WLAN_CONNECTION_ATTRIBUTES));

            // Do something here with the connection info....    
            WlanFreeMemory(ptr);
        }
        }
        finally
        {
        if (handle != IntPtr.Zero)
            WlanCloseHandle(handle, IntPtr.Zero);
        }

VB.NET

     Dim handle As IntPtr = IntPtr.Zero
     Dim negotiatedVersion As UInteger
     Try
     If WlanOpenHandle(1, IntPtr.Zero, negotiatedVersion, handle) <> 0 Then
         Return
     End If

     Dim ptr As New IntPtr()
     If WlanEnumInterfaces(handle, IntPtr.Zero, ptr) <> 0 Then
         Return
     End If

     Dim infoList As New WLAN_INTERFACE_INFO_LIST(ptr)
     WlanFreeMemory(ptr)

     Dim guid As Guid
     Dim dataSize As UInteger
     Dim connection As WLAN_CONNECTION_ATTRIBUTES
     ' Call wlanqueryinterface for all the interfaces in the list
     For i As Integer = 0 To infoList.dwNumberOfItems - 1
         guid = infoList.InterfaceInfo(i).InterfaceGuid
         If WlanQueryInterface(handle, guid, WLAN_INTF_OPCODE.wlan_intf_opcode_current_connection, IntPtr.Zero, dataSize, ptr, _
         IntPtr.Zero) <> 0 Then
         Return
         End If

         connection = DirectCast(Marshal.PtrToStructure(ptr, GetType(WLAN_CONNECTION_ATTRIBUTES)), WLAN_CONNECTION_ATTRIBUTES)

         ' Do something here with the connection info....
         WlanFreeMemory(ptr)
     Next
     Finally
     If handle <> IntPtr.Zero Then
         WlanCloseHandle(handle, IntPtr.Zero)
     End If
     End Try