/// <summary>
/// Http上传文件
/// </summary>
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());

    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(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;
}

using System;
using System.Web;

namespace SWX
{
    public partial class test2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            HttpPostedFile file = Request.Files[0];
            file.SaveAs(MapPath("\\UploadFile\\" + file.FileName));
            Response.Write("Success\r\n");
        }
    }
}