利用WebRequest类上传文件

说明：1.WebRequest类是一个抽象类，所以上传类实际使用的是其子类

2.打开Fiddler软件，监视正常网页的文件上传，可以看到http协议的请求和响应信息，简略说明

（第一行：请求说明

POST http://localhost/UpLoad.aspx HTTP/1.1 （请求类型：post，请求地址: http://localhost/UpLoad.aspx，http协议类型：HTTP/1.1）

第二行至多行：请求头（一系列的 key:value）

User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Content-Type: multipart/form-data;charset=utf-8;boundary=8D30475B6E5BB4C
Host:localhost
Content-Length: 22194
Expect: 100-continue
Connection: Close

换行，第n行：请求体

响应类似，详细见fiddler。

3.通过查看fiddler监测的http请求过程，可以利用webrequest模拟http请求，代码如下：

 private void UploadFile(string  path)
    {
        try
        {
            if (!string.IsNullOrEmpty(path))
            {
                string filename = Path.GetFileName(path); //获取文件名称
                LogWrite("上传文件", "开始上传文件，文件名称" + filename, null);
                string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线               
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost/UpLoad.aspx");
                request.ServicePoint.ConnectionLimit = 50; //设置最大连接数
                request.ServicePoint.Expect100Continue = false;//解决webexception操作超时

                request.Method = "POST"; //请求方法
                #region ==请求头===
                request.KeepAlive = false; //请求连接方式，设置为请求完成后断开连接
                request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0";
                request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
                request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
                #endregion             
                byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");//分割线数据
                byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");//结束分割线数据
                StringBuilder sbHeader = new StringBuilder(string.Format("Content-Disposition:form-data;name=\"file\";filename=\"{0}\"\r\nContent-Type:application/octet-stream\r\n\r\n", filename));
                byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sbHeader.ToString()); //上传文件头数据
                string sbheader2 = string.Format("Content-Disposition:form-data;name=\"ws\"\r\n\r\nother");//其他的form表单数据,这里为：form["ws"]="other"
                byte[] ddd = Encoding.UTF8.GetBytes(sbheader2);
                FileStream fs = new FileStream(path, FileMode.Open);//读取文件
                byte[] bArr = new byte[fs.Length];
                long filesize = fs.Length;
                fs.Read(bArr, 0, (int)filesize);
                fs.Close();
                request.ContentLength = itemBoundaryBytes.Length * 2 + ddd.Length + postHeaderBytes.Length + filesize + endBoundaryBytes.Length;//设置请求长度，一定要设置，否则可能会引发请求超时的异常
                Stream sm = request.GetRequestStream(); //获取请求流
                sm.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);//写入分割线数据
                sm.Write(ddd, 0, ddd.Length); //写入表单数据
                sm.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);//写入分割线数据
                sm.Write(postHeaderBytes, 0, postHeaderBytes.Length);//写入上传文件头数据

                long size = 0;
                float percent = 0; //上传进度
                //分步上传
                while (size < filesize)
                {
                    if (filesize - size > 1024)
                    {
                        sm.Write(bArr, (int)size, 1024); 
                        size += 1024;
                    }
                    else
                    {
                        sm.Write(bArr, (int)size, (int)(filesize - size));
                        size = filesize;
                    }
                    percent = size / (float)filesize;
                }
                //sm.Write(bArr, 0, bArr.Length);


                sm.Write(endBoundaryBytes, 0, endBoundaryBytes.Length); //写入结束分割线
                sm.Close();
                HttpWebResponse response = (HttpWebResponse)request.GetResponse(); //获取响应
                Stream sss = response.GetResponseStream();
                LogWrite("上传文件", response.StatusCode.ToString() + filename, null);

                //Stream sss = request.GetResponse().GetResponseStream();
                StreamReader sr = new StreamReader(sss);
                string ret = sr.ReadToEnd();
                sr.Close();
                LogWrite("上传文件", "结束上传文件，返回结果" + ret, null);
                //资源释放
                response.Close();
                request.Abort();
                System.GC.Collect();
            }
        }
        catch (Exception ex)
        {
            LogWrite("上传文件发生异常", "", ex);          
        }

    }

4.注意：一定要设置request.ContentLength的大小，否则可能引发操作超时的异常信息。