对于和一般的WinAPI交互来说，没必要这么麻烦，可以使用StructLayout和MarshalAs解决：

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using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace ConsoleApplication5
{
    class Program
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        public struct RtlOSVersionInfoExW
        {
            public uint dwOSVersionInfoSize;
            public uint dwMajorVersion;
            public uint dwMinorVersion;
            public uint dwBuildNumber;
            public uint dwPlatformId;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
            public string szCSDVersion;
            public ushort wServicePackMajor;
            public ushort wServicePackMinor;
            public ushort wSuiteMask;
            public byte wProductType;
            public byte wReserved;
        }

        [DllImport("ntdll.dll")]
        public static extern bool RtlGetVersion(ref RtlOSVersionInfoExW osver);

        static void Main(string[] args)
        {
            RtlOSVersionInfoExW osvex = new RtlOSVersionInfoExW();
            osvex.dwOSVersionInfoSize = (uint)Marshal.SizeOf(osvex);
            RtlGetVersion(ref osvex);
            Console.WriteLine(osvex.dwMajorVersion);
            Console.WriteLine(osvex.dwMinorVersion);
            Console.WriteLine(osvex.dwBuildNumber);
            Console.WriteLine(osvex.dwPlatformId);
            Console.WriteLine(osvex.szCSDVersion);
            Console.WriteLine(osvex.wServicePackMajor);
            Console.WriteLine(osvex.wServicePackMinor);
            Console.WriteLine(osvex.wSuiteMask);
            Console.WriteLine(osvex.wProductType);
            Console.WriteLine(osvex.wReserved);
        }
    }
}

/// <summary>
/// 结构体 值类型转byte数组
/// BitConverter
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="structObj"></param>
/// <returns></returns>
public static byte[] StructToBytes<T>(this T structObj) where T : struct
{
int size = System.Runtime.InteropServices.Marshal.SizeOf(structObj);
byte[] bytes = new byte[size];

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        IntPtr structPtr = System.Runtime.InteropServices.Marshal.AllocHGlobal(size);
        System.Runtime.InteropServices.Marshal.StructureToPtr(structObj, structPtr, true);
        System.Runtime.InteropServices.Marshal.Copy(structPtr, bytes, 0, size);
        System.Runtime.InteropServices.Marshal.FreeHGlobal(structPtr);
        return bytes;
    }
    /// <summary>
    /// byte数组转 结构体 值类型
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="bytes">
    /// <returns></returns>
    public static T BytesToStuct<t>(this byte[] bytes) where T : struct
    {
        int size = System.Runtime.InteropServices.Marshal.SizeOf(default(T));
        if (size > bytes.Length)
        {
            return default(T);
        }
        IntPtr structPtr = System.Runtime.InteropServices.Marshal.AllocHGlobal(size);
        System.Runtime.InteropServices.Marshal.Copy(bytes, 0, structPtr, size);
        T obj = (T)System.Runtime.InteropServices.Marshal.PtrToStructure(structPtr, typeof(T));
        System.Runtime.InteropServices.Marshal.FreeHGlobal(structPtr);

        return obj;
    }
</t>

/// <summary>
/// 把对象序列化并返回相应的字节
/// </summary>
/// <param name="pObj">需要序列化的对象</param>
/// <returns>byte[]</returns>
static public byte[] SerializeObject(this object pObj)
{
if (pObj == null)
return null;
System.IO.MemoryStream _memory = new System.IO.MemoryStream();
BinaryFormatter formatter = new BinaryFormatter();
formatter.Serialize(_memory, pObj);
_memory.Position = 0;
byte[] read = new byte[_memory.Length];
_memory.Read(read, 0, read.Length);
_memory.Close();
return read;
}

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    /// <summary>
    /// 把字节反序列化成相应的对象
    /// </summary>
    /// <param name="pBytes">字节流
    /// <returns>object</returns>
    static public T DeserializeObject<t>(this byte[] pBytes)
    {
        T _newOjb ;
        if (pBytes == null || pBytes.Length < 1) return default(T);
        System.IO.MemoryStream _memory = new System.IO.MemoryStream(pBytes);
        _memory.Position = 0;
        BinaryFormatter formatter = new BinaryFormatter();
        _newOjb = (T)formatter.Deserialize(_memory);
        _memory.Close();
        return _newOjb;
    }
</t>

引用 张静茹 : /// <summary> /// 结构体 值类型转byte数组 /// BitConverter /// </summary> ///……

写个算法也要用到互操作性，总感觉不爽。。。

InteropServices.Marshal Methods are probably the fastest way to manipulate bytes directly from memory in .NET