从c#调用C结构数据

我已经从dev c++制作了一个dll。我想调用这个函数。开发c++代码如下:

//the head file
struct sAdd
{
int* aarr;
int* barr;
int length;
};
DLLIMPORT int AddStruct (struct sAdd*);
//the c file
 DLLIMPORT int AddStruct (struct sAdd* sadd)
{//sum the aarr and the barr and return the result.
          int sum=0;
          int* aarr=sadd->aarr;
          int* barr=sadd->barr;
         int numArr=sadd->length;      
          int i;
          for(i=0;i<numArr;i++)
          sum+=*(aarr+i);
          i=0;
          for(i=0;i<numArr;i++)
          sum+=*(barr+i);
          return sum;       
}

为了调用AddStruct函数，我需要首先定义一个结构体。

public struct sAdd
{
    public int[] a;
    public int[] b;
    public int length;
}
  [DllImport("DllMain.dll", CallingConvention = CallingConvention.Cdecl)]
  public static extern int AddStruct(ref sAdd sadd);

调用AddStruct函数的代码如下:

    sAdd sadd = new sAdd();
    sadd.a = new int[4] { 1, 2, 3 ,4};
    sadd.b = new int[4] { 1, 2, 3 ,4};
    sadd.length=4;
    Console.WriteLine("sAdd:" + AddStruct(ref sadd).ToString());

的结果应该是20，但我得到一个37109984或其他一些大数字。因此，我不确定如何更改代码以获得正确的结果。也许我需要使用IntPtr或其他方式??谢谢。

最后，我处理了这个问题。

  [StructLayout(LayoutKind.Sequential)]
  public struct sAdd
  {
      public IntPtr a;
      public IntPtr b;
     public int length;
  };
            sAdd sadd = new sAdd();
            int[] a = new int[4] { 1, 2, 3 ,4};
             int[] b = new int[4] { 1, 2, 3 ,4};
            sadd.length = 4;
            sadd.a = Marshal.UnsafeAddrOfPinnedArrayElement(a, 0);
            sadd.b = Marshal.UnsafeAddrOfPinnedArrayElement(b, 0);
            Console.WriteLine("sAdd:" + DllMainWrapper.AddStruct(ref sadd).ToString());

int* aarr=sadd->aarr;
int* barr=sadd->barr;
int numAarr=sizeof(aarr)/sizeof(int);
int numBarr=sizeof(barr)/sizeof(int);