Problems reading array in struct

Hi, I'm trying to marshal the DS_SELECTION_LIST struct (http://msdn.microsoft.com/library/default.asp url=/library/en-us/ad/ad/ds_selection_list.asp) to C#. It works, but only the first element is retrieved. I believe this is because the marshaler can not determine the array size.

However, the field cItems in the struct determines the array size. But I can not use the SizeParamIndex with UnmanagedType.ByValArray. So I tried the UnmanagedType.LPArray but then I receive the exception: System.TypeLoadException: Cannot marshal field 'aDsSelection' of type 'ADHelper.DS_SELECTION_LIST': Invalid managed/unmanaged type combination (Arrays fields must be paired with ByValArray or SafeArray).

How should I decorate the aDsSelection field to have the marshaler retrieve it as a dynamic array of DS_SELECTION structs

Here is the code for the struct in C#

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]

internal struct DS_SELECTION_LIST

[MarshalAs(UnmanagedType.U4)]

public int cItems;

[MarshalAs(UnmanagedType.U4)]

public int cFetchedAttributes;

[MarshalAs(UnmanagedType.ByValArray, ArraySubType = UnmanagedType.Struct)]

public DS_SELECTION[] aDsSelection;