pdf 下载整理

pdf下载整理：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Net;

namespace PdfDownload
{
    /// <summary>
    /// PDF 下载工具
    /// </summary>
    public class PDF : IHttpHandler
    {
        public void ProcessRequest(HttpContext context)
        {
            var url = context.Request["url"];
            var title = context.Request["title"];
            var response = context.Response;
            if (!string.IsNullOrEmpty(url) && !string.IsNullOrEmpty(title))
            {
                response.Charset = System.Text.Encoding.UTF8.ToString();
                response.ContentEncoding = System.Text.Encoding.UTF8;
                try
                {
                    HttpWebRequest request = (HttpWebRequest)System.Net.WebRequest.Create(url);
                    request.Timeout = 5000;
                    request.ReadWriteTimeout = 1000;
                    request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36";
                    request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8";
                    using (var remoteResponse = request.GetResponse())
                    {
                        var length = remoteResponse.ContentLength;
                        if (length != -1)
                        {
                            response.ContentType = "application/pdf";
                            response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(title));
                            response.AppendHeader("Content-Length", length.ToString());
                            byte[] buffer = new byte[512 * 1024];
                            using (var stream = remoteResponse.GetResponseStream())
                            {
                                var position = 0;
                                while ((position = stream.Read(buffer, 0, buffer.Length)) > 0)
                                {
                                    response.OutputStream.Write(buffer, 0, position);
                                }
                            }
                            response.Flush();
                            return;
                        }
                    }
                }
                catch (Exception ex)
                {
                    response.ContentType = "html/text";
                    System.Text.StringBuilder builder = new System.Text.StringBuilder();
                    builder.Append("URL:");
                    builder.AppendLine(url);
                    builder.AppendLine(ex.ToString());
                    response.Write(builder.ToString());
                }
            }
            else
            {
                context.Response.StatusCode = 404;
            }
        }

        public string GetWindSessionID(HttpContext context)
        {
            string str = context.Request.Headers["wind.sessionid"];
            if (string.IsNullOrEmpty(str))
            {
                str = context.Request.QueryString["wind.sessionid"];
                if (string.IsNullOrEmpty(str) && (context.Request.Cookies["wind.sessionid"] != null))
                {
                    str = context.Request.Cookies["wind.sessionid"].Value;
                }
            }
            return str;
        }

        public bool IsReusable
        {
            get
            {
                return true;
            }
        }
    }
}