[C#]在WinForm下使用HttpWebRequest上傳檔案並顯示進度

這段時間因項目需要，要實現WinForm下的檔案上傳，個人覺得採用FTP方法太麻煩，還得配置FTP伺服器，要通過防火牆也是一個麻煩。本來打算採用WebClient方法，但是採用這個方法實現後，進度條很短時間後就達到最大值，要等待一段時間才能傳送完畢，要是檔案太大（我這裡測試約100M），會出現錯誤。後來才知道，原來WebClient是在載入完整個檔案到記憶體後才真正開始上傳，怪不得會出現前面的問題了。不得已參考了很多文章，老外的一個文章對我啟發很大（http://blogs.msdn.com/johan/archive/2006/11/15/are-you-getting-outofmemoryexceptions-when-uploading-large-files.aspx），是採用HttpWebRequest方法實現的。廢話少說，開始進入正題。實現過程如下：

在WinForm裡面調用下面的方法來上傳檔案：

// <summary>
        /// 將本地檔案上傳到指定的伺服器(HttpWebRequest方法)
        /// </summary>
        /// <param name="address">檔案上傳到的伺服器</param>
        /// <param name="fileNamePath">要上傳的本地檔案（全路徑）</param>
        /// <param name="saveName">檔案上傳後的名稱</param>
        /// <param name="progressBar">上傳進度條</param>
        /// <returns>成功返回1，失敗返回0</returns>
        private int Upload_Request(string address, string fileNamePath, string saveName, ProgressBar progressBar)
        {
            int returnValue = 0;

            // 要上傳的檔案
            FileStream fs = new FileStream(fileNamePath, FileMode.Open, FileAccess.Read);
            BinaryReader r = new BinaryReader(fs);

            //時間戳記
            string strBoundary = "----------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + strBoundary + "\r\n");

            //要求標頭部資訊
            StringBuilder sb = new StringBuilder();
            sb.Append("--");
            sb.Append(strBoundary);
            sb.Append("\r\n");
            sb.Append("Content-Disposition: form-data; name=\"");
            sb.Append("file");
            sb.Append("\"; filename=\"");
            sb.Append(saveName);
            sb.Append("\"");
            sb.Append("\r\n");
            sb.Append("Content-Type: ");
            sb.Append("application/octet-stream");
            sb.Append("\r\n");
            sb.Append("\r\n");
            string strPostHeader = sb.ToString();
            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(strPostHeader);

            // 根據uri建立HttpWebRequest對象
            HttpWebRequest httpReq = (HttpWebRequest)WebRequest.Create(new Uri(address));
            httpReq.Method = "POST";

            //對發送的資料不使用緩衝
            httpReq.AllowWriteStreamBuffering = false;

            //設定獲得響應的逾時時間（300秒）
            httpReq.Timeout = 300000;
            httpReq.ContentType = "multipart/form-data; boundary=" + strBoundary;
            long length = fs.Length + postHeaderBytes.Length + boundaryBytes.Length;
            long fileLength = fs.Length;
            httpReq.ContentLength = length;
            try
            {
                progressBar.Maximum = int.MaxValue;
                progressBar.Minimum = 0;
                progressBar.Value = 0;

                //每次上傳4k
                int bufferLength = 4096;
                byte[] buffer = new byte[bufferLength];

                //已上傳的位元組數
                long offset = 0;

                //開始上傳時間
                DateTime startTime = DateTime.Now;
                int size = r.Read(buffer, 0, bufferLength);
                Stream postStream = httpReq.GetRequestStream();

                //發送要求標頭部訊息
                postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
                while (size > 0)
                {
                    postStream.Write(buffer, 0, size);
                    offset += size;
                    progressBar.Value = (int)(offset * (int.MaxValue / length));
                    TimeSpan span = DateTime.Now - startTime;
                    double second = span.TotalSeconds;
                    lblTime.Text = "已用時：" + second.ToString("F2") + "秒";
                    if (second > 0.001)
                    {
                        lblSpeed.Text = " 平均速度：" + (offset / 1024 / second).ToString("0.00") + "KB/秒";