文件常用操作

一、删除文件/文件夹

　　当服务器上某些文件太多了，需要删除超过一定时间的文件

if(Directory.Exists(yourPath))
{
   //获取指定路径下所有文件夹
   string[] folderPaths = Directory.GetDirectories(yourPath);
   foreach(string folderPath in folderPaths)
           Directory.Delete(folderPath, true);
   //获取指定路径下所有文件
   string[] filePaths = Directory.GetFiles(yourPath);
   foreach(string filePath in filePaths)
           File.Delete(filePath);
}
//或者
DirectoryInfo folder = new DirectoryInfo(selectPath);
 txtFilesPath.Text = selectPath;
  foreach (FileInfo file in folder.GetFiles())
   {
//删除超过一定时间的文件
   if ((DateTime.Today - file.CreationTime).TotalDays   > dayCount)
              {
                File.Delete(file.FullName);
               }
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如果你需要连你指定的文件夹一起删除 就简单的多 如下

if(Directory.Exists(yourPath)){

Directory.Delete(yourPath,true);

 }

上述两例中的yourPath应为指定文件夹的路径 如: D: est 

第一例则会删除test文件夹下的所有子项

第二例则是test文件夹及其子项一起删除 需要注意的是Directory.Delete方法有两个重载 举例说明:

Directory.Delete(yourPath); //如果yourPath有子项 则删除失败 抛出异常

Directory.Delete(yourPath,true); //第二个为bool类型参数 表示是否需要使用递归删除 

补充说明 如果只是需要删除文件 就使用File类 如下

 if(File.Exists(filePath))

File.Delete(filePath) 

上例中的filePath为文件的完整路径 如: C: est est.txt

二、获取文件字节流

　　远程http(s)文件

HttpWebResponse.ContentLength 报异常：算术运算导致溢出

 

改为：

using (HttpWebResponse wr = (HttpWebResponse)req.GetResponse())
                {
                    Stream stream = wr.GetResponseStream();
                    //读取到内存
                    MemoryStream stmMemory = new MemoryStream();
                    byte[] buffer1 = new byte[1024 * 100];
                    int i;
                    //将字节逐个放入到Byte 中
                    while ((i = stream.Read(buffer1, 0, buffer1.Length)) > 0)
                    {
                        stmMemory.Write(buffer1, 0, i);
                    }
                    arraryByte = stmMemory.ToArray();
                    stmMemory.Close();
                    stream.Close();
                }
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三、web文件上传，webapi后台接收

后台

 public string Post()
        {
            string key = HttpContext.Current.Request["key"];
            string value = HttpContext.Current.Request["value"];
            HttpFileCollection files = HttpContext.Current.Request.Files;
 
            foreach (string f in files.AllKeys)
            {
                HttpPostedFile file = files[f];
                if (string.IsNullOrEmpty(file.FileName) == false)
                    file.SaveAs(HttpContext.Current.Server.MapPath("~/App_Data/") + file.FileName);
            }
 
            return key + value;
        }
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前端

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title></title>
</head>
<body>
    <form name="form" action="http://localhost:31855/api/values" method="post" enctype="multipart/form-data">
        <input type="text" name="key" id="txtKey" />
        <br />
        <input type="text" name="value" id="txtValue" />
        <br />
        <input type="file" name="file" id="upFile" />
        <input type="file" name="file2" id="File1" />
        <br />
        <input type="submit" id="btnSubmit" value="Submit" />
    </form>
</body>
</html>
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四、使用FormData对象实现ajax提交表单及文件上传，api处理

1、html代码

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <title>文件上传表单ajax提交模拟</title>
</head>
<body>
    <form id="postForm">
        <h2>文件上传表单ajax提交模拟</h2>
        <p>
            ajax提交给后端WebAPI处理，进而交给别人提供的第三方接口处理
        </p>
        <p>文件名：<input type="text" name="filename" /></p>
        <p>  文件： <input type="file" name="my_file" /></p>
        <input type="button" value="提交" onclick="btnPost()" />
    </form>

</body>
</html>
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2、jquery代码：

 <script src="Scripts/jquery-3.3.1.min.js"></script>
    <script>
        function btnPost() {
            var formData = new FormData($("#postForm")[0]);
            $.ajax({
                url: "http://localhost/uploadfile/api/UpFile",
                data: formData,
                type: "POST",
                contentType: false,
                processData: false,
                success: function (msg) {
                    alert(msg);  
                },
                error: function (e) {
                }
            });
        }
    </script>
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3、后台webapi处理

 [HttpPost]
        public  FileUploadResult UploadFile()
        {
            var name = HttpContext.Current.Request.Form["filename"];  //手动填写的文件名
            if (HttpContext.Current.Request.Files.Count <= 0)
            {
                return new FileUploadResult() { ErrorMessage = "沒有文件" };
            }
            var postFile = HttpContext.Current.Request.Files[0];
            var fileName = postFile.FileName; //实际的文件名（含扩展名）
            var ext = Path.GetExtension(fileName).Substring(1);
            fileName = DateTime.Now.ToString("yyyyMMddHHssmmfff") + "." + fileName;

            //Stream转为byte[]
            //byte[] fileBytes = null;
            //using (var ms = new MemoryStream())
            //{
            //    postFile.InputStream.CopyTo(ms);
            //    fileBytes = ms.ToArray();
            //}

            //或者
            byte[] fileBytes = new byte[postFile.InputStream.Length];
            postFile.InputStream.Read(fileBytes, 0, fileBytes.Length);

            var uploadResult = new EditFile().UploadFile(fileName, fileBytes);

            if (uploadResult.success)
            {
                return new FileUploadResult() { success =true,clientUrl=uploadResult.clientUrl };
            }
            else
            {
                return new FileUploadResult() { success = false, clientUrl = uploadResult.ErrorMessage };
            }
        }
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进一步处理代码省略..

using (HttpWebResponse wr = (HttpWebResponse)req.GetResponse())
                {
                    Stream stream = wr.GetResponseStream();
                    //读取到内存
                    MemoryStream stmMemory = new MemoryStream();
                    byte[] buffer1 = new byte[1024 * 100];
                    int i;
                    //将字节逐个放入到Byte 中
                    while ((i = stream.Read(buffer1, 0, buffer1.Length)) > 0)
                    {
                        stmMemory.Write(buffer1, 0, i);
                    }
                    arraryByte = stmMemory.ToArray();
                    stmMemory.Close();
                    stream.Close();
                }
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五、FTP文件下载

　　从FTP文件服务器中下载文件，含用户名和密码

/// <summary>
    /// 下载图片保存在本地
    /// </summary>
    /// <param name="filePath">文件全路径</param>
    /// <param name="fileName">取出IP和port的文件路径和文件名</param>
    /// <param name="ftpUserID">FTP站点用户名</param>
    /// <param name="ftpPassword">TFP站点密码</param>
    /// <returns></returns>
    public static bool Download(string filePath, string fileName, string ftpUserID, string ftpPassword)
    {
        string serverPath = HttpContext.Current.Server.MapPath("/");
        string subserverPath = serverPath.Substring(0, serverPath.Length - 1);
        string localPath = subserverPath + fileName; //含文件名的全路径
        string path = Path.GetDirectoryName(localPath); //不含文件名的路径
        FtpWebRequest reqFTP;
        try
        {
            // FileStream outputStream = new FileStream(fileName, FileMode.Create);
            FileStream outputStream;
            reqFTP = (FtpWebRequest)FtpWebRequest.Create(new Uri(filePath));
            reqFTP.Method = WebRequestMethods.Ftp.DownloadFile;
            reqFTP.UseBinary = true;
            reqFTP.UsePassive = false;
            reqFTP.Credentials = new NetworkCredential(ftpUserID, ftpPassword);
            FtpWebResponse response = (FtpWebResponse)reqFTP.GetResponse();
            Stream ftpStream = response.GetResponseStream();
            if (File.Exists(localPath))
            {
                outputStream = File.Open(localPath, FileMode.Open, FileAccess.ReadWrite);
            }
            else
            {
                if (!Directory.Exists(path))
                {
                    Directory.CreateDirectory(path);
                }
                outputStream = File.Create(localPath);
            }
            long cl = response.ContentLength;
            int bufferSize = 2048;
            int readCount;
            byte[] buffer = new byte[bufferSize];
            readCount = ftpStream.Read(buffer, 0, bufferSize);
            while (readCount > 0)
            {
                outputStream.Write(buffer, 0, readCount);
                readCount = ftpStream.Read(buffer, 0, bufferSize);
            }
            ftpStream.Close();
            outputStream.Close();
            response.Close();
            return true;

        }
        catch (Exception ex)
        {
            return false;
            throw new Exception("FtpHelper Download Error --> " + ex.Message);
        }
    }
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原文地址：https://www.cnblogs.com/peterYong/p/9599631.html