以下程序在.NET2005，系統XP中測試通過：

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using System.Net;

using System.IO;

namespace TQSystem.Com

{

    class UpDownLoadFile

    {

        /// <summary>

        /// WebClient上傳文件至服務器（不帶進度條）

        /// </summary>

        /// <param name="fileNameFullPath">要上傳的文件（全路徑格式）</param>

        /// <param name="strUrlDirPath">Web服務器文件夾路徑</param>

        /// <returns>True/False是否上傳成功</returns>

        public bool UpLoadFile(string fileNameFullPath, string strUrlDirPath)

        {

            //得到要上傳的文件文件名

            string fileName = fileNameFullPath.Substring(fileNameFullPath.LastIndexOf("\\") 1);

            //新文件名由年月日時分秒及毫秒組成

            string NewFileName = DateTime.Now.ToString("yyyyMMddhhmmss")

                                        DateTime.Now.Millisecond.ToString()

                                        fileNameFullPath.Substring(fileNameFullPath.LastIndexOf("."));

            //得到文件擴展名

            string fileNameExt = fileName.Substring(fileName.LastIndexOf(".") 1);

            if (strUrlDirPath.EndsWith("/") == false) strUrlDirPath = strUrlDirPath "/";

            //保存在服務器上時，將文件改名（示業務需要）

            strUrlDirPath = strUrlDirPath NewFileName;

            // 創建WebClient實例

            WebClient myWebClient = new WebClient();

            myWebClient.Credentials = CredentialCache.DefaultCredentials;

            // 將要上傳的文件打開讀進文件流

            FileStream myFileStream = new FileStream(fileNameFullPath, FileMode.Open, FileAccess.Read);

            BinaryReader myBinaryReader = new BinaryReader(myFileStream);

            try

            {

                byte[] postArray = myBinaryReader.ReadBytes((int)myFileStream.Length);

                //打開遠程Web地址，將文件流寫入

                Stream postStream = myWebClient.OpenWrite(strUrlDirPath, "PUT");

                if (postStream.CanWrite)

                {

                    postStream.Write(postArray, 0, postArray.Length);

                }

                else

                {

                    //MessageBox.Show("Web服務器文件目前不可寫入，請檢查Web服務器目錄權限設置！","系統提示",MessageBoxButtons.OK,MessageBoxIcon.Information);

                }

                postStream.Close();//關閉流

                return true;

            }

            catch (Exception exp)

            {

                //MessageBox.Show("文件上傳失敗：" exp.Message, "系統提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                return false;

            }

        }

        /// <summary>

        /// 下載服務器文件至客戶端（不帶進度條）

        /// </summary>

        /// <param name="strUrlFilePath">要下載的Web服務器上的文件地址（全路徑　如：http://www.dzbsoft.com/test.rar）</param>

        /// <param name="Dir">下載到的目錄（存放位置，機地機器文件夾）</param>

        /// <returns>True/False是否上傳成功</returns>

        public bool DownLoadFile(string strUrlFilePath, string strLocalDirPath)

        {

            // 創建WebClient實例

            WebClient client = new WebClient();

            //被下載的文件名

            string fileName = strUrlFilePath.Substring(strUrlFilePath.LastIndexOf("/"));

            //另存為的絕對路徑＋文件名

            string Path = strLocalDirPath fileName;

            try

            {

                WebRequest myWebRequest = WebRequest.Create(strUrlFilePath);

            }

            catch (Exception exp)

            {

                MessageBox.Show("文件下載失敗：" exp.Message, "系統提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

            }

            try

            {

                client.DownloadFile(strUrlFilePath, Path);

                return true;

            }

            catch (Exception exp)

            {

                MessageBox.Show("文件下載失敗：" exp.Message, "系統提示", MessageBoxButtons.OK, MessageBoxIcon.Information);

                return false;

            }

        }

        /// <summary>

        /// 下載帶進度條代碼（普通進度條）

        /// </summary>

        /// <param name="URL">網址</param>

        /// <param name="Filename">文件名</param>

        /// <param name="Prog">普通進度條ProgressBar</param>

        /// <returns>True/False是否下載成功</returns>

        public bool DownLoadFile(string URL, string Filename, ProgressBar Prog)

        {

            try

            {

                System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL); //從URL地址得到一個WEB請求   

                System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)Myrq.GetResponse(); //從WEB請求得到WEB響應   

                long totalBytes = myrp.ContentLength; //從WEB響應得到總字節數   

                Prog.Maximum = (int)totalBytes; //從總字節數得到進度條的最大值   

                System.IO.Stream st = myrp.GetResponseStream(); //從WEB請求創建流（讀）   

                System.IO.Stream so = new System.IO.FileStream(Filename, System.IO.FileMode.Create); //創建文件流（寫）   

                long totalDownloadedByte = 0; //下載文件大小   

                byte[] by = new byte[1024];

                int osize = st.Read(by, 0, (int)by.Length); //讀流   

                while (osize > 0)

                {

                    totalDownloadedByte = osize totalDownloadedByte; //更新文件大小   

                    Application.DoEvents();

                    so.Write(by, 0, osize); //寫流   

                    Prog.Value = (int)totalDownloadedByte; //更新進度條   

                    osize = st.Read(by, 0, (int)by.Length); //讀流   

                }

                so.Close(); //關閉流

                st.Close(); //關閉流

                return true;

            }

            catch

            {

                return false;

            }

        }

        /// <summary>

        /// 下載帶進度條代碼(狀態欄式進度條）

        /// </summary>

        /// <param name="URL">網址</param>

        /// <param name="Filename">文件名</param>

        /// <param name="Prog">狀態欄式進度條ToolStripProgressBar</param>

        /// <returns>True/False是否下載成功</returns>

        public bool DownLoadFile(string URL, string Filename, ToolStripProgressBar Prog)

        {

            try

            {

                System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL); //從URL地址得到一個WEB請求   

                System.Net.HttpWebResponse myrp = (System.Net.HttpWebResponse)Myrq.GetResponse(); //從WEB請求得到WEB響應   

                long totalBytes = myrp.ContentLength; //從WEB響應得到總字節數   

                Prog.Maximum = (int)totalBytes; //從總字節數得到進度條的最大值   

                System.IO.Stream st = myrp.GetResponseStream(); //從WEB請求創建流（讀）   

                System.IO.Stream so = new System.IO.FileStream(Filename, System.IO.FileMode.Create); //創建文件流（寫）   

                long totalDownloadedByte = 0; //下載文件大小   

                byte[] by = new byte[1024];

                int osize = st.Read(by, 0, (int)by.Length); //讀流   

                while (osize > 0)

                {

                    totalDownloadedByte = osize totalDownloadedByte; //更新文件大小   

                    Application.DoEvents();

                    so.Write(by, 0, osize); //寫流   

                    Prog.Value = (int)totalDownloadedByte; //更新進度條   

                    osize = st.Read(by, 0, (int)by.Length); //讀流   

                }

                so.Close(); //關閉流   

                st.Close(); //關閉流   

                return true;

            }

            catch

            {

                return false;

            }

        }

    }

}