Marshalling nested array of structure in C#

How would you marshall this nested array of structure in C#?

C struct:

typedef struct
{
    unsigned int appVersionNumber;
    unsigned int networkId;
    struct
    {
        int code;
        int endDate;
    } profiles[4];
} CardEnvHolder;

My C# attempt:

[StructLayout(LayoutKind.Sequential)]
unsafe struct CardEnvHolder
{
    public uint appVersionNumber;
    public uint networkId;
    public Profiles[] profiles;
}

[StructLayout(LayoutKind.Sequential)]
struct Profiles 
{
    public int code;
    public int endDate;
}

C# Main:

unsafe 
{
    CardEnvHolder envhold = new CardEnvHolder();
    void* ptr = (void*)&envhold; //Error here
    EnvHolderTest(ptr);
    Console.WriteLine(envhold.profil[1].code);
}

Unfortunately I get the error CS0208 "Cannot take the address of, get the size of, or declare a pointer to a managed type ('T')"

As requested,

EnvHolder C function:

void EnvHoldInit(CardEnvHolder* envhold)
{
    envhold->appVersionNumber = 4;
    envhold->networkId = 8;
    envhold->profiles[1].code = 84;
    printf("%d\n", envhold->profiles[1].code);
    envhold->profiles[1].code++;
}

EXPORT void EnvHolderTest(void* envhold)
{
    EnvHoldInit(envhold);
}

EnvHolder C# prototype:

[DllImport("Sandbox.dll", CallingConvention = CallingConvention.Cdecl)]
extern static unsafe void EnvHolderTest([In, Out] void* envhold);