winform里文件上传不了

Question

我找一个早上的代码用了
        
                            string file_cus = picMake_path.ToString();                            string file_ser = ftp_url + "Audit/1.jpg";
                            //+ "\\" + pic_url.ToString();                            // 要上传的文件
                            FileStream fs = new FileStream(file_cus, FileMode.Open, FileAccess.Read);
                            
                            BinaryReader r = new BinaryReader(fs);                            byte[] postArray = r.ReadBytes((int)fs.Length);                            //MessageBox.Show(file_cus.ToString() + "@@@@" + file_ser.ToString());                            Uri uri = new Uri(file_ser);
                            webClient.Credentials = CredentialCache.DefaultCredentials;                            Stream postStream = webClient.OpenWrite(file_ser, "PUT");
                            if (postStream.CanWrite)
                            {
                                //这里的bytes就是本地文件转化为二进制的数组 
                                postStream.Write(postArray, 0, postArray.Length);
                                MessageBox.Show(file_cus.ToString() + "@@@@" + file_ser.ToString());
                            }
                            else
                            {
                                MessageBox.Show("文件目前不可写！");
                            }
                            postStream.Close();//就是提示在WebClient 请求期间发生异常
试了很多都是这样服务器的权限也对的
谁能告诉我怎么上传文件啊