HRESULT WINAPI BluetoothGATTGetServices(
  _In_      HANDLE               hDevice,
  _In_      USHORT               ServicesBufferCount,
  _Out_opt_ PBTH_LE_GATT_SERVICE ServicesBuffer,
  _Out_     USHORT               *ServicesBufferActual,
  _In_      ULONG                Flags
);

typedef struct _BTH_LE_GATT_SERVICE {
  BTH_LE_UUID ServiceUuid;
  USHORT      AttributeHandle;
} BTH_LE_GATT_SERVICE, *PBTH_LE_GATT_SERVICE;

typedef struct _BTH_LE_UUID {
  BOOLEAN IsShortUuid;
  USHORT  ShortUuid;
  GUID    LongUuid;
} BTH_LE_UUID, *PBTH_LE_UUID;

[StructLayout(LayoutKind.Sequential)]
        struct BTH_LE_UUID
        {
            public Boolean IsShortUuid;
            public ushort ShortUuid;
            public Guid LongUuid;
        };

        [StructLayout(LayoutKind.Sequential)]
        struct BTH_LE_GATT_SERVICE
        {
            public BTH_LE_UUID ServiceUuid;
            public ushort AttributeHandle;
        };


[DllImport("BluetoothApis.dll", PreserveSig = false)]
        static extern long BluetoothGATTGetServices(
            IntPtr hDevice,
            ushort ServicesBufferCount,
            out BTH_LE_GATT_SERVICE ServicesBuffer,
            ref ushort ServicesBufferActual,
            ulong Flags
        );

BTH_LE_GATT_SERVICE le_gatt_service = new BTH_LE_GATT_SERVICE();

long result = BluetoothGATTGetServices(hLEDevice, 0, out le_gatt_service, ref serviceBufferCount, BLUETOOTH_GATT_FLAG_NONE);

A call to PInvoke function 'BLE_Sniffer!BLE_Sniffer.BLE::BluetoothGATTGetServices' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

[DllImport("BluetoothApis.dll", PreserveSig = false, CallingConvention = CallingConvention.Cdecl)]
        static extern long BluetoothGATTGetServices(
            IntPtr hDevice,
            ushort ServicesBufferCount,
            out BTH_LE_GATT_SERVICE ServicesBuffer,
            ref ushort ServicesBufferActual,
            ulong Flags
        );