下载网页中远程图片的方法

在网站内容编辑时, 经常会把别的网站的内容COPY后再PASTE到自己的后台编辑中, 但是其中的图片只是保存的URL, 并未COPY到本地. 下面这个方法能把COPY回来的HTML代码中的图片的URL转换成指定的URL, 并把图片下载到指定的物理路径.

using System;
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Net;
using System.IO;

namespace EFPlatform.Helper
{
    public class WebRequestHelper
    {
        #region RequestFileFromHtml
        public static string RequestFileFromHtml(string html, string fileUrl, string filePath, string reservedHost)
        {
            Uri url;
            string fileExt;
            string fileName;
            WebClient c = new WebClient();
            string p = @"((http|https|ftp):(\/\/|\\\\){1}(([A-Za-z0-9_-])+[.]){1,}(net|com|cn|org|cc|tv|[0-9]{1,3})(\S*\/)((\S)+[.]{1}(gif|jpg|png)))";
            Regex r = new Regex(p, RegexOptions.Compiled | RegexOptions.IgnoreCase);
            MatchCollection mc = r.Matches(html);

            if(mc.Count > 0)
            {
                List<Uri> urlList = new List<Uri>();
                int matchIndex = 0;
                bool repeated = false;

                for(int i = 0;i < mc.Count;i++)
                {
                    url = new Uri(mc[i].Value);

                    for(int j = 0;j < urlList.Count;j++)
                    {
                        if(url == urlList[j])
                        {
                            repeated = true;
                            break;
                        }
                    }

                    if(!repeated && (url.Host.ToLower() != reservedHost.ToLower()))
                    {
                        urlList.Add(url);
                        matchIndex++;
                    }
                }

                for(int i = 0;i < urlList.Count;i++)
                {
                    url = urlList[i];
                    fileExt = url.AbsoluteUri.Substring(url.AbsoluteUri.LastIndexOf("."));
                    fileName = string.Format("{0:yyMMddHHmmssff}{1}{2}", DateTime.Now, i, fileExt);

                    try
                    {
                        c.DownloadFile(url, filePath + fileName);
                        html = html.Replace(url.AbsoluteUri, fileUrl + fileName);
                    }
                    catch
                    {
                    }
                }
            }

            return html;
        } 
        #endregion
    }

}