i have a struct with dynamic length [StructLayout(LayoutKind.Sequential, Pack = 1)] struct PktAck { public Int32 code; [MarshalAs(UnmanagedType.LPStr)] public string text; } when i'm converting bytes[] to struct by: GCHandle handle = GCHandle.Alloc(value, GCHandleType.Pinned); stru = (T)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(T)); handle.Free(); i have a error, because size of struct less than size of bytes[] and "string text" is pointer to string... how can i use dynamic strings? or i can use only this: [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]