WlanHostedNetworkQuerySecondaryKey

[DllImport("wlanapi.dll", SetLastError = true)]
public static extern uint WlanHostedNetworkQuerySecondaryKey(
   IntPtr hClientHandle,
   IntPtr pdwKeyLength,
   IntPtr ppucKeyData,
   IntPtr pbIsPassPhrase,
   IntPtr pbPersistent,
   IntPtr pdwReasonCode,
   IntPtr pReserved
);

Microsoft documentation: Link