如何在C＃中使用Regexp替换出现的任何情况 <img> 给定字符串中带有ALT参数的HTML标记

Question

我有一个字符串，其中包含许多与该结构完全相同的HTML标记：

Hello <img src="./images/foo.gif" alt="bar"> World!
<img src="./images/foo2.gif" alt="bar2">

包含该标记的字符串是从外部工具自动生成的，并且保证完全具有该标记的声明

现在我希望用“alt”参数替换给定字符串中的这种标记的每个出现，因此对于上面的示例结果应该是：

Hello bar World!
bar2

我正在使用C＃和.NET Framework

Answer 1

使用Expresso ，我设计了以下表达式：

<img src="[^"]*" alt="([^"]*)">

显然，这需要生成的标记与您的示例完全匹配，因此生成标记的内容的任何更改都将导致该标记中断。 因此，建议您考虑使用类似HtmlAgilityPack的产品代替正则表达式来解决此问题。

这是Expresso使用许多用法示例生成的代码。

//  using System.Text.RegularExpressions;

/// <summary>
///  Regular expression built for C# on: Mon, Nov 22, 2010, 03:51:18 PM
///  Using Expresso Version: 3.0.2766, http://www.ultrapico.com
///  
///  A description of the regular expression:
///  
///  <img src="
///      <img
///      Space
///      src="
///  Any character that is NOT in this class: ["], any number of repetitions
///  " alt="
///      "
///      Space
///      alt="
///  [1]: A numbered capture group. [[^"]*]
///      Any character that is NOT in this class: ["], any number of repetitions
///  ">
///      ">
///  
///
/// </summary>
public static Regex regex = new Regex(
      "<img src=\"[^\"]*\" alt=\"([^\"]*)\">",
      RegexOptions.Compiled
    );


// This is the replacement string
public static string regexReplace = "$1";


//// Replace the matched text in the InputText using the replacement pattern
// string result = regex.Replace(InputText,regexReplace);

//// Split the InputText wherever the regex matches
// string[] results = regex.Split(InputText);

//// Capture the first Match, if any, in the InputText
// Match m = regex.Match(InputText);

//// Capture all Matches in the InputText
// MatchCollection ms = regex.Matches(InputText);

//// Test to see if there is a match in the InputText
// bool IsMatch = regex.IsMatch(InputText);

//// Get the names of all the named and numbered capture groups
// string[] GroupNames = regex.GetGroupNames();

//// Get the numbers of all the named and numbered capture groups
// int[] GroupNumbers = regex.GetGroupNumbers();