Array of structs marshaled as null

[drvic10k]

I have a problem with marshaling this type

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
public struct DataAds
{
    [MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.Struct, SizeConst = 4)]
    public StructAds[] Structs;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
public struct StructAds
{
    public int Field1;

    public int Field2;

    public int Field3;

    public int Field4;
}

when marshaling in AdsSymbolicServer like this: _symbolMarshaler.TryMarshal(symbol, value, span, out int _)

I get the property Structs=null

Am I missing some attributes?

[RalfHeitmann]

The SymbolMarshaler doesn't need external classes to Marshal the symbol. The Symbol itself contains all information how to marshal the data. I have extended the AdsSymbolicServerSample with additional code that demonstrates accessing structs.