[StructLayout(LayoutKind.Sequential)] 
    public struct STAGINFOPARAM
    {
        byte metaData;

        UInt16 uEPCLength;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
        Byte[] ucaEPC;

        UInt16 uTagCRC;
    };

    [StructLayout(LayoutKind.Sequential)]
    public struct SREADINVENTORYTAGINFORSPPARAM
    {
        Byte ucStatus;

        UInt16 uMetadataFlag;
        Byte ucOption;
        Byte ucTagCount;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0)]  // 如这里改为  SizeConst = 1 运行就不会出错
        STAGINFOPARAM[] tagInfo;
    };

    
    Int32 nSize2 = Marshal.SizeOf(typeof(SREADINVENTORYTAGINFORSPPARAM)); // 一运行到这里就出错？
    MessageBox.Show(nSize2.ToString());