asp.net(C#)自动下载站外图片
一般情况下，大多数用户在转载网络上文章时，都会将文章内的图片下载到自己的服务器上！但是当图片数量很多的时候，这就变成了一个苦力活了！
本文正是在该情况下，来实现程序自动下载站外地图！
在上代码前，先讲下具体实现原理：
第一步：通过正则表达式找出所有图片地址
第二步：通过图片地址的域名与当前访问地址的域名进行比较判断是否外链图片
第三步：使用System.Net下的WebClient下载图片到指定目录！
第四步：替换链接地址
:::: {#highlighter_88540 .syntaxhighlighter .csharp} ::: toolbar ?{.toolbar_item .command_help .help} :::
+--------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+
| ::: {.line .number1 .index0 .alt2} | ::::::::::::::::::::::::::::::::::::::::::::::::::::: container |
| 1 | ::: {.line .number1 .index0 .alt2} |
| ::: | {.csharp .spaces}protected{.csharp .keyword} string{.csharp .keyword} BatchDownloadPicture({.csharp |
| | .plain}string{.csharp .keyword} html,{.csharp .plain}string{.csharp .keyword} savePath,{.csharp |
| ::: {.line .number2 .index1 .alt1} | .plain}string{.csharp .keyword} rootUrl){.csharp .plain} |
| 2 | ::: |
| ::: | |
| | ::: {.line .number2 .index1 .alt1} |
| ::: {.line .number3 .index2 .alt2} | {.csharp .spaces}{{.csharp .plain} |
| 3 | ::: |
| ::: | |
| | ::: {.line .number3 .index2 .alt2} |
| ::: {.line .number4 .index3 .alt1} | {.csharp .spaces}List<Uri> result = {.csharp .plain}new{.csharp .keyword} List<Uri>();{.csharp .plain} |
| 4 | ::: |
| ::: | |
| | ::: {.line .number4 .index3 .alt1} |
| ::: {.line .number5 .index4 .alt2} | |
| 5 | ::: |
| ::: | |
| | ::: {.line .number5 .index4 .alt2} |
| ::: {.line .number6 .index5 .alt1} | {.csharp .spaces}System.Text.RegularExpressions.Regex objRegExp = {.csharp .plain}new{.csharp |
| 6 | .keyword} System.Text.RegularExpressions.Regex({.csharp |
| ::: | .plain}@"(<img[^>]*?src\s*=\s*(['""]?))([^'""\s>]+)([^>]*>)"{.csharp |
| | .string}, System.Text.RegularExpressions.RegexOptions.IgnoreCase);{.csharp .plain} |
| ::: {.line .number7 .index6 .alt2} | ::: |
| 7 | |
| ::: | ::: {.line .number6 .index5 .alt1} |
| | |
| ::: {.line .number8 .index7 .alt1} | ::: |
| 8 | |
| ::: | ::: {.line .number7 .index6 .alt2} |
| | {.csharp .spaces}System.Text.RegularExpressions.MatchCollection mc = objRegExp.Matches(html);{.csharp .plain} |
| ::: {.line .number9 .index8 .alt2} | ::: |
| 9 | |
| ::: | ::: {.line .number8 .index7 .alt1} |
| | |
| ::: {.line .number10 .index9 .alt1} | ::: |
| 10 | |
| ::: | ::: {.line .number9 .index8 .alt2} |
| | {.csharp .spaces}Uri uri;{.csharp .plain} |
| ::: {.line .number11 .index10 .alt2} | ::: |
| 11 | |
| ::: | ::: {.line .number10 .index9 .alt1} |
| | |
| ::: {.line .number12 .index11 .alt1} | ::: |
| 12 | |
| ::: | ::: {.line .number11 .index10 .alt2} |
| | {.csharp .spaces}for{.csharp .keyword} ({.csharp .plain}int{.csharp |
| ::: {.line .number13 .index12 .alt2} | .keyword} i = 0; i < mc.Count; i++){.csharp .plain} |
| 13 | ::: |
| ::: | |
| | ::: {.line .number12 .index11 .alt1} |
| ::: {.line .number14 .index13 .alt1} | {.csharp .spaces}{{.csharp .plain} |
| 14 | ::: |
| ::: | |
| | ::: {.line .number13 .index12 .alt2} |
| ::: {.line .number15 .index14 .alt2} | {.csharp .spaces}uri = {.csharp .plain}new{.csharp .keyword} Uri(mc[i].Groups[3].Value);{.csharp .plain} |
| 15 | ::: |
| ::: | |
| | ::: {.line .number14 .index13 .alt1} |
| ::: {.line .number16 .index15 .alt1} | {.csharp .spaces}if{.csharp .keyword} (mc[i].Groups[3].Value.IndexOf({.csharp .plain}"://"{.csharp |
| 16 | .string}) != -1 && !result.Contains(uri) && !Request.Url.Host.Equals(uri.Host, StringComparison.OrdinalIgnoreCase)){.csharp |
| ::: | .plain} |
| | ::: |
| ::: {.line .number17 .index16 .alt2} | |
| 17 | ::: {.line .number15 .index14 .alt2} |
| ::: | {.csharp .spaces}result.Add(uri);{.csharp .plain} |
| | ::: |
| ::: {.line .number18 .index17 .alt1} | |
| 18 | ::: {.line .number16 .index15 .alt1} |
| ::: | {.csharp .spaces}}{.csharp .plain} |
| | ::: |
| ::: {.line .number19 .index18 .alt2} | |
| 19 | ::: {.line .number17 .index16 .alt2} |
| ::: | |
| | ::: |
| ::: {.line .number20 .index19 .alt1} | |
| 20 | ::: {.line .number18 .index17 .alt1} |
| ::: | {.csharp .spaces}using{.csharp .keyword} (System.Net.WebClient wc = {.csharp .plain}new{.csharp |
| | .keyword} System.Net.WebClient()){.csharp .plain} |
| ::: {.line .number21 .index20 .alt2} | ::: |
| 21 | |
| ::: | ::: {.line .number19 .index18 .alt2} |
| | {.csharp .spaces}{{.csharp .plain} |
| ::: {.line .number22 .index21 .alt1} | ::: |
| 22 | |
| ::: | ::: {.line .number20 .index19 .alt1} |
| | {.csharp .spaces}string{.csharp .keyword} extension;{.csharp .plain} |
| ::: {.line .number23 .index22 .alt2} | ::: |
| 23 | |
| ::: | ::: {.line .number21 .index20 .alt2} |
| | {.csharp .spaces}int{.csharp .keyword} index;{.csharp .plain} |
| ::: {.line .number24 .index23 .alt1} | ::: |
| 24 | |
| ::: | ::: {.line .number22 .index21 .alt1} |
| | {.csharp .spaces}string{.csharp .keyword} name;{.csharp .plain} |
| ::: {.line .number25 .index24 .alt2} | ::: |
| 25 | |
| ::: | ::: {.line .number23 .index22 .alt2} |
| | {.csharp .spaces}foreach{.csharp .keyword} (Uri node {.csharp .plain}in{.csharp |
| ::: {.line .number26 .index25 .alt1} | .keyword} result){.csharp .plain} |
| 26 | ::: |
| ::: | |
| | ::: {.line .number24 .index23 .alt1} |
| ::: {.line .number27 .index26 .alt2} | {.csharp .spaces}{{.csharp .plain} |
| 27 | ::: |
| ::: | |
| | ::: {.line .number25 .index24 .alt2} |
| ::: {.line .number28 .index27 .alt1} | {.csharp .spaces}try{.csharp .keyword} |
| 28 | ::: |
| ::: | |
| | ::: {.line .number26 .index25 .alt1} |
| ::: {.line .number29 .index28 .alt2} | {.csharp .spaces}{{.csharp .plain} |
| 29 | ::: |
| ::: | |
| | ::: {.line .number27 .index26 .alt2} |
| ::: {.line .number30 .index29 .alt1} | {.csharp .spaces}index = node.AbsolutePath.LastIndexOf({.csharp .plain}'.'{.csharp |
| 30 | .string});{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number31 .index30 .alt2} | ::: {.line .number28 .index27 .alt1} |
| 31 | {.csharp .spaces}if{.csharp .keyword} (index > 0){.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number32 .index31 .alt1} | ::: {.line .number29 .index28 .alt2} |
| 32 | {.csharp .spaces}{{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number33 .index32 .alt2} | ::: {.line .number30 .index29 .alt1} |
| 33 | {.csharp .spaces}extension = node.AbsolutePath.Substring(index);{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number34 .index33 .alt1} | ::: {.line .number31 .index30 .alt2} |
| 34 | {.csharp .spaces}}{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number35 .index34 .alt2} | ::: {.line .number32 .index31 .alt1} |
| 35 | {.csharp .spaces}else{.csharp .keyword} |
| ::: | ::: |
| | |
| ::: {.line .number36 .index35 .alt1} | ::: {.line .number33 .index32 .alt2} |
| 36 | {.csharp .spaces}{{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number37 .index36 .alt2} | ::: {.line .number34 .index33 .alt1} |
| 37 | {.csharp .spaces}continue{.csharp .keyword};{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number38 .index37 .alt1} | ::: {.line .number35 .index34 .alt2} |
| 38 | {.csharp .spaces}}{.csharp .plain} |
| ::: | ::: |
| | |
| ::: {.line .number39 .index38 .alt2} | ::: {.line .number36 .index35 .alt1} |
| 39 | {.csharp .spaces}name = {.csharp .plain}string{.csharp |
| ::: | .keyword}.Concat(Guid.NewGuid().ToString({.csharp .plain}"N"{.csharp .string}), extension);{.csharp .plain} |
| | ::: |
| ::: {.line .number40 .index39 .alt1} | |
| 40 | ::: {.line .number37 .index36 .alt2} |
| ::: | |
| | ::: |
| ::: {.line .number41 .index40 .alt2} | |
| 41 | ::: {.line .number38 .index37 .alt1} |
| ::: | {.csharp .spaces}wc.DownloadFile(node, {.csharp .plain}string{.csharp |
| | .keyword}.Concat(savePath, name));{.csharp .plain} |
| ::: {.line .number42 .index41 .alt1} | ::: |
| 42 | |
| ::: | ::: {.line .number39 .index38 .alt2} |
| | |
| ::: {.line .number43 .index42 .alt2} | ::: |
| 43 | |
| ::: | ::: {.line .number40 .index39 .alt1} |
| | {.csharp .spaces}html = html.Replace(node.ToString(), {.csharp .plain}string{.csharp |
| ::: {.line .number44 .index43 .alt1} | .keyword}.Concat(rootUrl, name));{.csharp .plain} |
| 44 | ::: |
| ::: | |
| | ::: {.line .number41 .index40 .alt2} |
| ::: {.line .number45 .index44 .alt2} | {.csharp .spaces}}{.csharp .plain} |
| 45 | ::: |
| ::: | |
| | ::: {.line .number42 .index41 .alt1} |
| ::: {.line .number46 .index45 .alt1} | {.csharp .spaces}catch{.csharp .keyword} |
| 46 | ::: |
| ::: | |
| | ::: {.line .number43 .index42 .alt2} |
| ::: {.line .number47 .index46 .alt2} | {.csharp .spaces}{{.csharp .plain} |
| 47 | ::: |
| ::: | |
| | ::: {.line .number44 .index43 .alt1} |
| ::: {.line .number48 .index47 .alt1} | {.csharp .spaces}continue{.csharp .keyword};{.csharp .plain} |
| 48 | ::: |
| ::: | |
| | ::: {.line .number45 .index44 .alt2} |
| ::: {.line .number49 .index48 .alt2} | {.csharp .spaces}}{.csharp .plain} |
| 49 | ::: |
| ::: | |
| | ::: {.line .number46 .index45 .alt1} |
| ::: {.line .number50 .index49 .alt1} | {.csharp .spaces}}{.csharp .plain} |
| 50 | ::: |
| ::: | |
| | ::: {.line .number47 .index46 .alt2} |
| | {.csharp .spaces}}{.csharp .plain} |
| | ::: |
| | |
| | ::: {.line .number48 .index47 .alt1} |
| | |
| | ::: |
| | |
| | ::: {.line .number49 .index48 .alt2} |
| | {.csharp .spaces}return{.csharp .keyword} html;{.csharp .plain} |
| | ::: |
| | |
| | ::: {.line .number50 .index49 .alt1} |
| | {.csharp .spaces}}{.csharp .plain} |
| | ::: |
| | ::::::::::::::::::::::::::::::::::::::::::::::::::::: |
+--------------------------------------+-------------------------------------------------------------------------------------------------------------------------------+
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