C#调用C++dll报错ACCESS VIOLATION

原帖地址：http://bbs.csdn.net/topics/391012458
代码改了一下，问题还没有解决。于是重开一个贴

-----------------------------------------------------C#代码

namespace WpfApplication2

{

    class MyClass1 : INotifyPropertyChanged  

    {     

    public MyClass1()

    {

        result="null";

    }

    private string result;



    public string Result

    {

        get { return result; }

        set { result = value;

            if (PropertyChanged != null)

            {

                this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Result"));

            }

        }

        

    }

    public event PropertyChangedEventHandler PropertyChanged;

    }

    /// <summary>

    /// MainWindow.xaml 的交互逻辑

    /// </summary>

  

    public class mytransdll 

    {

        [DllImport("mytransdll.dll", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Cdecl)]

        public static extern int mytransfunc(StringBuilder exportpath, StringBuilder importpath);

    }

    public partial class Main : Window

    {



        MyClass1 myout=new MyClass1 ();       

        private StringBuilder exportpath;        

        private StringBuilder importpath;      

        public Main()

        {

            InitializeComponent();

            myout.Result = "there will show ,if transform is ok ";// Result 赋值应该放到Main的构造函数或者窗口的Loaded事件中赋值的。

           //把结果binding上去。。。请注意，XAML里的binding并不能访问C#里的变量，而C#里的变量却可以访问XAML

            Binding bind1 = new Binding();

            bind1.Source = myout;                    

            bind1.Path = new PropertyPath("Result");

            this.MyLabel.SetBinding(Label.ContentProperty, bind1);  



        

        }

       private void Button_Click_2(object sender, RoutedEventArgs e)

        {

            //int isornotsuccess = 1;

           

            int isornotsuccess = mytransdll.mytransfunc(exportpath, importpath);

             myout.Result = " Transforming,please wait....";

            Binding bind3 = new Binding();

            bind3.Source = myout;

            bind3.Path = new PropertyPath("Result");

            this.MyLabel.SetBinding(Label.ContentProperty, bind3);    //按下按钮之后马上显示正在传输

             if (isornotsuccess == 1)

            {

                myout.Result = exportpath.ToString() ;

                Binding bind2 = new Binding();                   

                bind2.Source = myout;

                bind2.Path = new PropertyPath("Result");

                this.MyLabel.SetBinding(Label.ContentProperty, bind2);                //这里写成功后的反应

            }

        }



        private void textBox1_KeyDown_1(object sender, KeyEventArgs e)

        {

            if (e.Key == Key.Enter) //key是一个类，这是一个类的判断

            {

                StringBuilder exportpath=new StringBuilder(this.textBox1.Text,200);

                 

                

            }

        }

---------------------------------------------------C++编写的DLL

//



#include "stdafx.h"

#include "stdio.h"

#include"pcap.h"

#include<WinSock.h>

#include"packet32.h"

#include<Win32-Extensions.h>

#include "stdlib.h"







extern "C" _declspec(dllimport) int mytransfunc(char* exportpath,char* importpath);

int mytransfunc(char* exportpath,char* importpath)

{

//和EXPORTPATH无关的代码

	char A[]="regenerate_original_picture.txt";

	char PA[1024];

	char exportpathvalue=*exportpath;

//！！！！高能，就是这句出问题。不管是用这种方法中转还是直接调用*exportpath都出现报错

	sprintf(PA,"%s\\%s",exportpathvalue,A);//连接字符串

	FILE *fpopen = fopen(PA, "rb");

//和EXPORTPATH无关的代码

}

-----------------------------------------问题
C#编写了一个UI界面，调用DLL的时候传入文件所在地址，然后由DLL对其操作
测试过DLL程序的正确性。

之前大神们说的，如使用stringbuilder，DllImport函数的参数的设定都不管用。有网友说是关于托管代码和非托管代码内存管理的问题。。。楼主是新手，不太明白，还请指教。