C# 文件上传（HttpWebRequest）文件下载

最新推荐文章于 2024-09-15 17:40:28 发布

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最新推荐文章于 2024-09-15 17:40:28 发布

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分类专栏： C# 文章标签： c# 开发语言 java

本文链接：https://blog.youkuaiyun.com/weixin_39667153/article/details/129283713

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该代码段展示了如何使用C#进行文件上传和下载操作。文件上传通过HttpWebRequest创建请求，设置Content-Type，利用多部分表单数据处理文件和额外数据。文件下载部分使用WebClient类下载指定URL的文件到用户选择的本地路径。

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1、文件上传

        /// <summary>
        /// 上传文件
        /// </summary>
        /// <param name="url"></param>
        /// <param name="files"></param>
        /// <param name="data"></param>
        /// <param name="encoding"></param>
        /// <returns></returns>
        private string uploadFile(string url, string[] files, NameValueCollection data,Encoding encoding)
        {
            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundarybytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
            byte[] endbytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");

            //1.HttpWebRequest
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.ContentType = "multipart/form-data; boundary=" + boundary;
            request.Method = "POST";
            request.KeepAlive = true;
            request.Credentials = CredentialCache.DefaultCredentials;

            using (Stream stream = request.GetRequestStream())
            {
                //1.1 key/value
                string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
                if (data != null)
                {
                    foreach (string key in data.Keys)
                    {
                        stream.Write(boundarybytes, 0, boundarybytes.Length);
                        string formitem = string.Format(formdataTemplate, key, data[key]);
                        byte[] formitembytes = encoding.GetBytes(formitem);
                        stream.Write(formitembytes, 0, formitembytes.Length);
                    }
                }

                //1.2 file
                string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: application/octet-stream\r\n\r\n";
                byte[] buffer = new byte[4096];
                int bytesRead = 0;
                for (int i = 0; i < files.Length; i++)
                {
                    stream.Write(boundarybytes, 0, boundarybytes.Length);
                    string header = string.Format(headerTemplate, "file" + i, Path.GetFileName(files[i]));
                    byte[] headerbytes = encoding.GetBytes(header);
                    stream.Write(headerbytes, 0, headerbytes.Length);
                    using (FileStream fileStream = new FileStream(files[i], FileMode.Open, FileAccess.Read))
                    {
                        while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                        {
                            stream.Write(buffer, 0, bytesRead);
                        }
                    }
                }

                //1.3 form end
                stream.Write(endbytes, 0, endbytes.Length);
            }
            //2.WebResponse
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            using (StreamReader stream = new StreamReader(response.GetResponseStream()))
            {
                return stream.ReadToEnd();
            }
        }
        /// <summary>
        /// 上传
        /// </summary>
        /// <param name="path">文件地址</param>
        /// <returns></returns>
        private void Upload(string path){
            string url = ( GetConnstr() + "CrPpt/Upload");
            NameValueCollection data = new NameValueCollection();
            data.Set("Id","1111111");
            string[] files = new string[] { path };
            Encoding encoding = Encoding.UTF8;
            uploadFile(url, files,data,encoding );
        }

2、文件下载

       private void test(List<Dictionary<string, string>> pptlist)
       {
            for( int i=0;i< pptlist.Count;i++)
            {
                Dictionary<string, string> ppt = pptlist[i];
                Button btn = new Button();
                btn.Text = ("ppt" + (i + 1));
                btn.Name = ppt["Fileurl"];
                btn.Click += new EventHandler(downloadFile);//注册点击事件
                //将Button在GroupBox容器中显⽰
                this.groupBox1.Controls.Add(btn);
            }
        }
        private void downloadFile(object sender, EventArgs e)
        {
            if (sender is Button)
            {
                Button button = sender as Button;
                //string url0 = button.Name;
                //System.Diagnostics.Debug.WriteLine(url0);
                string url = "https://pic.vjshi.com/2019-05-23/35a1a395f621988f1c5971a5d33ff0a3/00004.jpg?x-oss-process=style/watermark";
                string remoteUri = System.IO.Path.GetDirectoryName(url);
                string fileName = System.IO.Path.GetFileName(url);
                string myStringWebResource = null;
                WebClient myWebClient = new WebClient();
                myStringWebResource = url;
                FolderBrowserDialog dialog = new FolderBrowserDialog();
                dialog.Description = "请选择下载路径";
                string foldPath = "";
                if (dialog.ShowDialog() == DialogResult.OK)
                {
                    foldPath = dialog.SelectedPath;
                }
                if (string.IsNullOrEmpty(foldPath))
                {
                    MessageBox.Show("请选择下载路径");
                    return;
                }
                string fullfile = foldPath + "\\" + fileName;
                myWebClient.DownloadFile(myStringWebResource, fullfile);
                if (File.Exists(fullfile))//判断文件是否存在
                {
                    MessageBox.Show("下载成功");
                }
                else
                {
                    MessageBox.Show("下载失败");
                }
            }
           
        }