asp.net 动态加载dll的问题

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Runtime.InteropServices;



namespace dllImport

{

    public partial class Form1 : Form

    {

        [DllImport("kernel32.dll", EntryPoint = "LoadLibrary")]

        static extern int LoadLibrary([MarshalAs(UnmanagedType.LPStr)] string lpLibFileName);



        [DllImport("kernel32.dll", EntryPoint = "GetProcAddress")]

        static extern IntPtr GetProcAddress(int hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName);



        [DllImport("kernel32.dll", EntryPoint = "FreeLibrary")]

        static extern bool FreeLibrary(int hModule);



        delegate int GetBusinessData1(string inputData, ref StringBuilder outputdata);



        public Form1()

        {

            InitializeComponent();

        }



        private void Form1_Load(object sender, EventArgs e)

        {

            try

            {   string _dllpath = @"G:\program\dllImport\Project2.dll";

                string inputData = "1234";

                StringBuilder AOutputData = new StringBuilder(213273);



                int hModule = LoadLibrary(_dllpath);

                if (hModule == 0)

                    return;

                //得到指向Add函数的指针

                IntPtr intPtr = GetProcAddress(hModule, "GetBusinessData");

                GetBusinessData1 myfun = (GetBusinessData1)Marshal.GetDelegateForFunctionPointer(intPtr, typeof(GetBusinessData1));

                int iReturn = myfun(inputData, ref AOutputData);

                MessageBox.Show(AOutputData.ToString());



            }

            catch(Exception ex)

            {

                MessageBox.Show(ex.ToString());

            }

        }

    }

}