C#获取C++中修改过的float数组(指针)，dll

C++中

struct rankPoint{
    float sim;
};

extern "C" __declspec(dllexport) int getRank(rankPoint prank[20000]){    
    for(int i = 0; i < 20000; i++)
    prank[i].sim = 0;

    for(int i = 0; i < 7; i++)
    prank[i].sim = i;
    return 0;
}

C#中

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Runtime.InteropServices;


namespace DllTest
{
    [StructLayout(LayoutKind.Sequential)]
    struct rankP
    {
        public float mark;
    }
    public class Cpp {
        [DllImport("Cdll.dll")]
        public static extern int getRank(IntPtr p);
    }
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            int size = Marshal.SizeOf(typeof(rankP)) * 20000;
            byte[] bytes = new byte[size];
            IntPtr pBuff = Marshal.AllocHGlobal(size);
            rankP[] rBuf = new rankP[20000];
            Cpp.getRank(pBuff);
            for(int i = 0; i < 20000; i++)
            {
                IntPtr pPointor = new IntPtr(pBuff.ToInt64() + Marshal.SizeOf(typeof(rankP)) * i);
                rBuf[i] = (rankP)Marshal.PtrToStructure(pPointor,typeof(rankP));
            }
            int si = 0;  //设置断点监测，的确修改了rBuf数组，也就是实现了数组的传递，只不过是通过结构体实现的
            Marshal.FreeHGlobal(pBuff);
        }
    }

}

 转一篇简单易懂的C++编写dll的文档http://wenku.baidu.com/view/ebb7e1edb8f67c1cfad6b867.html