.net 模拟发起HTTP请求（用于上传文件）

　　用C#在服务端发起http请求，附上代码一

    /// <summary>
    /// 文件帮助类
    /// </summary>
    public class FileHelper
    {
        /// <summary>
        /// 上传文件
        /// </summary>
        /// <param name="url">请求地址</param>
        /// <param name="path">文件路径（带文件名）</param>
        /// <returns></returns>
        public static string HttpUploadFile(string url, string path)
        {
            // 设置参数
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            CookieContainer cookieContainer = new CookieContainer();
            request.CookieContainer = cookieContainer;
            request.AllowAutoRedirect = true;
            request.Method = "POST";
            string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线
            request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
            byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");
            byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

            int pos = path.LastIndexOf("\\");
            string fileName = path.Substring(pos + 1);

            //请求头部信息
            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());

            StringBuilder builder = new StringBuilder($"Content-Disposition:form-data;name=\"subPath\"\r\n\r\ntmswechat");
            byte[] postHeaderBytestwo = Encoding.UTF8.GetBytes(builder.ToString());

            FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Read);
            byte[] bArr = new byte[fs.Length];
            fs.Read(bArr, 0, bArr.Length);
            fs.Close();

            Stream postStream = request.GetRequestStream();
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
            postStream.Write(bArr, 0, bArr.Length);
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytestwo, 0, postHeaderBytestwo.Length);
            postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
            postStream.Close();

            //发送请求并获取相应回应数据
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            //直到request.GetResponse()程序才开始向目标网页发送Post请求
            Stream instream = response.GetResponseStream();
            StreamReader sr = new StreamReader(instream, Encoding.UTF8);
            //返回结果网页（html）代码
            string content = sr.ReadToEnd();
            return content;
        }

        /// <summary>
        /// 上传文件
        /// </summary>
        /// <param name="url">请求地址</param>
        /// <param name="fs">文件流</param>
        /// <param name="fileName">文件名</param>
        /// <returns></returns>
        public static string HttpUploadFile(string url, Stream fs, string fileName)
        {
            // 设置参数
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            CookieContainer cookieContainer = new CookieContainer();
            request.CookieContainer = cookieContainer;
            request.AllowAutoRedirect = true;
            request.Method = "POST";
            string boundary = DateTime.Now.Ticks.ToString("X"); // 随机分隔线
            request.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;
            byte[] itemBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "\r\n");
            byte[] endBoundaryBytes = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--\r\n");

            //请求头部信息
            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());

            StringBuilder builder = new StringBuilder($"Content-Disposition:form-data;name=\"subPath\"\r\n\r\ntmswechat");
            byte[] postHeaderBytestwo = Encoding.UTF8.GetBytes(builder.ToString());

            byte[] bArr = new byte[fs.Length];
            int len = fs.Read(bArr, 0, (int)fs.Length);

            Stream postStream = request.GetRequestStream();
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
            postStream.Write(bArr, 0, len);
            postStream.Write(itemBoundaryBytes, 0, itemBoundaryBytes.Length);
            postStream.Write(postHeaderBytestwo, 0, postHeaderBytestwo.Length);            
            postStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
            postStream.Close();

            //发送请求并获取相应回应数据
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            //直到request.GetResponse()程序才开始向目标网页发送Post请求
            Stream instream = response.GetResponseStream();
            StreamReader sr = new StreamReader(instream, Encoding.UTF8);
            //返回结果网页（html）代码
            string content = sr.ReadToEnd();
            return content;
        }
    }

 代码二

　　　　　public static string HttpClientUploadFile(string url, Stream fs, string fileName)
        {
            if (url.StartsWith("https"))
                System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
            HttpClient httpClient = new HttpClient();
            
            MultipartFormDataContent formData = new MultipartFormDataContent();
            
            byte[] bArr = new byte[fs.Length];
            fs.Read(bArr, 0, (int)fs.Length);
            fs.Seek(0, SeekOrigin.Begin);
            ByteArrayContent byteArrayContent = new ByteArrayContent(bArr);
            byteArrayContent.Headers.ContentEncoding.Add("utf-8");
            formData.Add(byteArrayContent, "file", fileName);
            formData.Add(new StringContent("tmswechat"), "subPath");
            HttpResponseMessage response = httpClient.PostAsync(url, formData).Result;
            if (response.IsSuccessStatusCode)
            {
                string result = response.Content.ReadAsStringAsync().Result;
                return result;
            }
            return null;
        }