如何写代码向ftp服务器传文件？

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using UnityEngine;

/// <summary>
/// 与 ftp 服务器通信的类
/// </summary>
public static class FtpHelper
{
    const int MaxReconnectCount = 3;        // 最大的重新连接次数
    static int s_reconnectCounter;

    static void ResetReconnectCounter()
    {
        s_reconnectCounter = 0;
    }

    static bool ReconnectCounterIncrease()
    {
        return ++s_reconnectCounter >= MaxReconnectCount;
    }

    /// <summary>
    /// 上传文件到 ftp 服务器
    /// </summary>
    /// <param name="srcFilePath">源文件路径</param>
    /// <param name="targetUrl">目标 url</param>
    /// <param name="credential">凭证</param>
    public static void UploadFileToFTPServer(string srcFilePath, string targetUrl, NetworkCredential credential)
    {
        if (string.IsNullOrEmpty(srcFilePath))
            throw new ArgumentException("srcFilePath");
        if (string.IsNullOrEmpty(targetUrl))
            throw new ArgumentException("targetUrl");
        if (credential == null)
            throw new ArgumentNullException("credential");

        targetUrl = FixUrl(targetUrl, false);

        try
        {
            FtpWebRequest request = (FtpWebRequest)WebRequest.Create(targetUrl);
            byte[] srcFileBuffer = File.ReadAllBytes(srcFilePath);

            request.Method = WebRequestMethods.Ftp.UploadFile;
            request.Credentials = credential;
            request.ContentLength = srcFileBuffer.Length;
            request.UseBinary = true;
            request.UsePassive = true;
            request.KeepAlive = false;

            using (Stream requestStream = request.GetRequestStream())
                requestStream.Write(srcFileBuffer, 0, srcFileBuffer.Length);

            Debug.Log(string.Format("Upload file succeed, source file path: {0}, target url: {1}", srcFilePath, targetUrl));

            ResetReconnectCounter();
        }
        catch (Exception ex)
        {
            string l = string.Format("Upload file failed, upload it again. source file path: {0}, target url: {1}, error message: {2}", srcFilePath, targetUrl, ex.Message);
            Debug.LogError(l);
            if (ReconnectCounterIncrease())
                throw new WebException(l);
            else
                UploadFileToFTPServer(srcFilePath, targetUrl, credential);
        }
    }

    /// <summary>
    /// 删除 ftp 服务器上的所有文件
    /// </summary>
    /// <param name="dirUrl">文件夹 url</param>
    public static void DeleteAllFilesOnFtp(string dirUrl, NetworkCredential credential)
    {
        if (string.IsNullOrEmpty(dirUrl))
            throw new ArgumentException("dirUrl");
        if (credential == null)
            throw new ArgumentNullException("credential");

        dirUrl = FixUrl(dirUrl, true);

        List<string> dirNames, fileNames;
        GetDirectoryList(dirUrl, credential, out dirNames, out fileNames);

        foreach (var dirName in dirNames)
        {
            string url = string.Format("{0}{1}/", dirUrl, dirName);
            DeleteAllFilesOnFtp(url, credential);
        }

        foreach (var fileName in fileNames)
        {
            string url = dirUrl + fileName;
            DeleteFile(url, credential);
        }
    }

    /// <summary>
    /// 获取 ftp 文件夹的列表
    /// </summary>
    public static void GetDirectoryList(string dirUrl, NetworkCredential credential, out List<string> dirNames, out List<string> fileNames)
    {
        if (string.IsNullOrEmpty(dirUrl))
            throw new ArgumentException("dirUrl");
        if (credential == null)
            throw new ArgumentNullException("credential");

        dirUrl = FixUrl(dirUrl, true);

        dirNames = new List<string>();
        fileNames = new List<string>();

        try
        {
            var request = (FtpWebRequest)WebRequest.Create(dirUrl);

            request.Method = WebRequestMethods.Ftp.ListDirectoryDetails;
            request.Credentials = credential;
            request.UseBinary = true;
            request.UsePassive = true;
            request.KeepAlive = false;

            var response = (FtpWebResponse)request.GetResponse();
            var responseStream = response.GetResponseStream();
            var responseReader = new StreamReader(responseStream);

            while (!responseReader.EndOfStream)
            {
                string line = responseReader.ReadLine();
                if (string.IsNullOrEmpty(line))
                    continue;

                string[] words = line.Split(new char[] { ‘ ‘ }, StringSplitOptions.RemoveEmptyEntries);
                string name = words.Last();

                if (line[0] == ‘d‘)         // 表示是文件夹
                    dirNames.Add(name);
                else if (line[0] == ‘-‘)    // 表示是文件
                    fileNames.Add(name);
            }

            responseReader.Dispose();
            response.Close();
            responseStream.Dispose();
        }
        catch (Exception ex)
        {
            string l = string.Format("Get directory list failed, directory url: {0}, error message: {1}", dirUrl, ex.Message);
            Debug.LogError(l);
            throw new WebException(l);
        }
    }

    /// <summary>
    /// 删除 ftp 服务器上的文件
    /// </summary>
    public static void DeleteFile(string fileUrl, NetworkCredential credential)
    {
        if (string.IsNullOrEmpty(fileUrl))
            throw new ArgumentException("fileUrl");
        if (credential == null)
            throw new ArgumentNullException("credential");

        fileUrl = FixUrl(fileUrl, false);

        try
        {
            var request = (FtpWebRequest)WebRequest.Create(fileUrl);

            request.Method = WebRequestMethods.Ftp.DeleteFile;
            request.Credentials = credential;
            request.UseBinary = true;
            request.UsePassive = true;
            request.KeepAlive = false;

            var response = request.GetResponse();
            response.Close();

            Debug.Log(string.Format("Delete file succeed, url: {0}", fileUrl));

            ResetReconnectCounter();
        }
        catch (Exception ex)
        {
            string l = string.Format("Delete file failed, url: {0}, error message: {1}", fileUrl, ex.Message);
            Debug.LogError(l);
            if (ReconnectCounterIncrease())
                throw new WebException(l);
            else
                DeleteFile(fileUrl, credential);
        }
    }

    /// <summary>
    /// 在 ftp 服务器上创建文件夹
    /// </summary>
    /// <param name="dirUrl"></param>
    /// <param name="credential"></param>
    public static void CreateFolder(string dirUrl, NetworkCredential credential)
    {
        if (string.IsNullOrEmpty(dirUrl))
            throw new ArgumentException("dirUrl");
        if (credential == null)
            throw new ArgumentNullException("credential");

        dirUrl = FixUrl(dirUrl, false);

        string folderName = Path.GetFileNameWithoutExtension(dirUrl);
        string parentFolderUrl = dirUrl.Replace(folderName, "");
        List<string> dirNames, fileNames;

        GetDirectoryList(parentFolderUrl, credential, out dirNames, out fileNames);

        if (dirNames.Contains(folderName))
            return;

        try
        {
            var request = (FtpWebRequest)WebRequest.Create(dirUrl);

            request.Method = WebRequestMethods.Ftp.MakeDirectory;
            request.Credentials = credential;
            request.UseBinary = true;
            request.UsePassive = true;
            request.KeepAlive = false;

            var response = request.GetResponse();
            response.Close();

            Debug.Log(string.Format("Create folder succeed, url: {0}", dirUrl));

            ResetReconnectCounter();
        }
        catch (Exception ex)
        {
            string l = string.Format("Create folder failed, create again, url: {0}, error message: {1}", dirUrl, ex.Message);
            Debug.LogError(l);
            if (ReconnectCounterIncrease())
                throw new WebException(l);
            else
                CreateFolder(dirUrl, credential);
        }
    }

    static string FixUrl(string url, bool endWithSprit)
    {
        if (string.IsNullOrEmpty(url))
        {
            return url;
        }

        url = url.Replace("\\", "/").TrimEnd(‘/‘);
        return endWithSprit ? url + "/" : url;
    }
}