c# FTP上传文件的问题 请高人指出问题。

Question

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Net;
using System.IO;
using System.Text;namespace ftp
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }        private void button1_Click(object sender, EventArgs e)
        {
            ftp.ftp_Upload("172.19.112.3","tx","tx953","D:\\2011.ISO");
            
        }        private void result_TextChanged(object sender, EventArgs e)
        {
            result.Text = ftp.ftp_Upload("172.19.112.3", "tx", "tx953", "D:\\2011.ISO").ToString();
        }
    }
    class ftp
    {
        public static bool ftp_Upload(string FtpURL, string username, string password, string FileName)
        {            string strTemp = FileName;
            strTemp = strTemp.Substring(strTemp.LastIndexOf(@"\") + 1);//截取文件名 
            Stream requestStream = null;
            FileStream fileStream = null;
            FtpWebResponse uploadResponse = null;
            try
            {
                string uu = "ftp://" + FtpURL + strTemp;
                FtpWebRequest uploadRequest = (FtpWebRequest)WebRequest.Create(uu);//创建完整的FTP服务地址
                uploadRequest.Method = WebRequestMethods.Ftp.UploadFile;  //设置FTP服务的操作为上载文件  
                uploadRequest.Proxy = null;     //服务器通信代理
                //设置用户名和密码
                uploadRequest.Credentials = new NetworkCredential(username, password);//用户名和密码
                requestStream = uploadRequest.GetRequestStream();
                fileStream = File.Open(FileName, FileMode.Open);//打开指定路径的文件
                byte[] buffer = new byte[4096];
                int nRead;
                while (true)//读取已打开文件的字节流写入缓冲区直至读取完毕
                {
                    nRead = fileStream.Read(buffer, 0, buffer.Length);
                    if (nRead == 0)
                        break;
                    requestStream.Write(buffer, 0, buffer.Length);
                }
                fileStream.Close();
                requestStream.Close();
                uploadResponse = (FtpWebResponse)uploadRequest.GetResponse();//服务器返回响应
            }
            catch (Exception e)
            {
                //MainForm.AddViewListValue("上传ftp失败" + e.Message, 5);
                Console.WriteLine("上传ftp失败" + e.Message, 5);
                return false;
            }
            finally
            {
                if (uploadResponse != null)
                    uploadResponse.Close();
                if (fileStream != null)
                    fileStream.Close();
                if (requestStream != null)
                    requestStream.Close();
            }
            return true;
        }
    }
}
窗体上有个button  有个textbox   希望实现点击button  上传文件  并在textbox返回结果  目前程序编译没有错误  但是无法上传文件   求问题解决办法。