static extern IntPtr BluetoothFindFirstRadio(ref Bluetooth_Find_Radio_Params pbtfrp,out IntPtr phRadio );

Bluetooth_Find_Radio_Params

    /// The BLUETOOTH_FIND_RADIO_PARAMS structure facilitates enumerating installed Bluetooth radios.

    /// <param name="pbtfrp">Pointer to a BLUETOOTH_FIND_RADIO_PARAMS structure</param>

  private struct Bluetooth_Find_Radio_Params

             this.dwSize = (UInt32)Marshal.SizeOf(typeof(Bluetooth_Find_Radio_Params));

Structure BLUETOOTH_FIND_RADIO_PARAMS