Ftp上传下载 C#

public class MyFtpClass
    {
        private readonly string _destIp;
        private readonly string _userName;
        private readonly string _password;
        public MyFtpClass(string desIp, string userName, string passowrd)
        {
            this._destIp = desIp;
            this._userName = userName;
            this._password = passowrd;
        }
        private FtpWebRequest OpenRequest(Uri uri,string ftpMethod)
        {
            FtpWebRequest request = WebRequest.Create(uri) as FtpWebRequest;
            if (request != null)
            {
                request.Credentials = new NetworkCredential(_userName, _password);
                request.UseBinary = true;
                request.Method = ftpMethod;
                return request;
            }
            else
            {
                return null;
            }
            
        }
        private FtpWebResponse OpenResponse(Uri uri, string ftpMethod)
        {
            FtpWebRequest request= this.OpenRequest(uri, ftpMethod);
            if (request != null)
            {
                FtpWebResponse response = request.GetResponse() as FtpWebResponse;
                return response;
            }
            else
            {
                return null;
            }
            
            
        }
        /// <summary>
        /// 要上传的本地文件路径
        /// </summary>
        /// <param name="uploadFilePath">形如：D:\folder1\2.jpg </param>
        /// <param name="desName">形如：123.jpg 或 subFolder1/123.jpg</param>
        /// <returns></returns>
        public bool Upload(string uploadFilePath, string desName)
        {
            Stream requestStream = null;
            FtpWebResponse response = null;
            try
            {
                Uri uri = new Uri(string.Format("ftp://{0}/{1}", _destIp, desName));
                FtpWebRequest request = OpenRequest(uri, WebRequestMethods.Ftp.UploadFile);
                requestStream = request.GetRequestStream();

                FileStream fs = File.Open(uploadFilePath, FileMode.Open);
                byte[] buff = new byte[1024];
                int buffRead = 0;
                while (true)
                {
                    int n = fs.Read(buff, buffRead, buff.Length);
                    if (n == 0)
                    {
                        break;
                    }
                    //把文件流写入请求流
                    requestStream.Write(buff, 0, n);
                }

                response = (FtpWebResponse)request.GetResponse();
                return true;
            }
            catch (Exception)
            {
                throw new Exception("上传文件失败！");
            }
            finally
            {
                requestStream.Close();
                response.Close();
            }
            
        }

        /// <summary>
        /// 下载文件
        /// </summary>
        /// <param name="serverFileName">要下载的文件名。形如：123.jpg 或 subFolder1/123.jpg</param>
        /// <param name="localPath">下载至本地的路径。形如： D:\a\b\</param>
        /// <param name="localName">保存在本地的名称。形如：3.jpg</param>
        /// <returns></returns>
        public bool Download(string serverFileName, string localPath, string localName)
        {
            Stream responseStream=null;
            FileStream fileStream=null;
            try
            {
                Uri uri = new Uri(string.Format("ftp://{0}/{1}", _destIp, serverFileName));
                FtpWebResponse downloadResponse = OpenResponse(uri, WebRequestMethods.Ftp.DownloadFile);
                responseStream = downloadResponse.GetResponseStream();
                fileStream = File.Create(localPath + localName);
                byte[] buffer = new byte[1024];
                while (true)
                {
                    var bytesRead = responseStream.Read(buffer, 0, buffer.Length);
                    if (bytesRead == 0)
                        break;
                    //把响应流写入文件
                    fileStream.Write(buffer, 0, bytesRead);
                }
                
                return true;
            }
            catch
            {
                throw new Exception("获取下载文件失败！");
            }
            finally
            {
                fileStream.Close();
                responseStream.Close();
            }
        }
    }

需要注意的流文件的读出和写入问题：
例如，

int n = fs.Read(buff, buffRead, buff.Length);
bufferRead和buff.Length指的是数组buff的索引以及长度。
流文件fs会自动维护一个指针Position，每当read n个字节时，会自动向后移动n个字节。

fileStream.Write(buffer, 0, bytesRead);是同样的道理。