MarshalDemo

using System;
using System.Runtime.InteropServices;

namespace MarshalDemo
{
    class Program
    {
        private static UserData userData;
        static void Main(string[] args)
        {
            userData.myString = "abc";
            userData.myInt = 100;

            int size = Marshal.SizeOf(userData);
            IntPtr pUserData = Marshal.AllocHGlobal(size);
            Marshal.StructureToPtr(userData, pUserData, true);

            UserData userData2 = (UserData)Marshal.PtrToStructure(pUserData, typeof(UserData));
            Marshal.FreeHGlobal(pUserData);

            Console.WriteLine(userData2.myString);
            Console.WriteLine(userData2.myInt);

            Console.Read();
        }
    }
    [System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential, CharSet = System.Runtime.InteropServices.CharSet.Ansi)]
    public struct UserData
    {
        [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = 15)]
        public string myString;
        public int myInt;
    }
}