.net - .net Regex.Replace 仅在指定的捕获组内

Question

是否可以使用 .net Regex 类对特定捕获组进行替换。

例如

<customer.*?(display="(?:yes|no)")?.*?>

我想在 Customer xml 元素上进行匹配，但在显示属性捕获组中进行替换。我认为那将是第 1 组，但我总是可以将其命名。

Answer 1

我认为您需要捕获显示属性之前和之后的内容。

(<customer.*?)(display="(?:yes|no)")(.*?>) 

然后你可以在你的替换 lambda 中使用它

Regex.Replace(inputString, @"(<customer.*?)(display=""(?:yes|no)"")(.*?>)", m => String.Format("{0}{1}{2}", m.Groups[1], /* replacement string based on m.Groups[2] */, m.Groups[3]));

Answer 2

根据安德鲁斯的回答，我通过创建一种处理替换的方法来扩展了这一点。在我的情况下，我想替换整个组，所以我创建了一个助手类来做到这一点。此外，它不需要您创建捕获前和捕获后组来实现此目的。

/// <summary>
/// A Regular Expression match and replace class
/// </summary>
public class RegexReplacer
{
    private readonly int _captureGroupToReplace;

    /// <summary>
    /// Initialises the RegEx replacer with matching criteria.
    /// </summary>
    /// <param name="name">A name that identifies this replacement pattern</param>
    /// <param name="matchCriteria">A regular Expression used to locate the values to replace</param>
    /// <param name="replacementValue">The value that will replace the matched pattern</param>
    /// <param name="captureGroupToReplace">The Capture group that should be replaced. The default is the entire match</param>
    public RegexReplacer(string name, Regex matchCriteria, string replacementValue, int captureGroupToReplace = 0)
    {
        _captureGroupToReplace = captureGroupToReplace;
        Name = name;
        ReplacementValue = replacementValue;
        MatchCriteria = matchCriteria;
    }

    public string Name { get; set; }

    public Regex MatchCriteria { get; set; }

    public string ReplacementValue { get; set; }

    /// <summary>
    /// Finds and replaces all instances of a string within the supplied string or replaces a group if the group id is supplied in the constructor
    /// </summary>
    public string ReplaceInString(string stringToSearch)
    {
        if (_captureGroupToReplace != 0)
            return MatchCriteria.Replace(stringToSearch, new MatchEvaluator(ReplaceGroup));

        return MatchCriteria.Replace(stringToSearch, ReplacementValue);
    }

    private string ReplaceGroup(Match match)
    {
        try
        {
            var matchedString = match.Value;
            //Match index is based on the original string not the matched string
            int groupIndex = match.Groups[_captureGroupToReplace].Index - match.Index;
            int groupLength = match.Groups[_captureGroupToReplace].Length;

            var preGroupString = matchedString.Substring(0, groupIndex);
            var postGroupString = matchedString.Substring(groupIndex + groupLength, matchedString.Length - (groupIndex + groupLength));

            var replacedString = String.Format("{0}{1}{2}", preGroupString, ReplacementValue, postGroupString);

            return replacedString;
        }
        catch (Exception)
        {
            return match.Value;
        }
    }
}

我还必须修改我的原始模式，这样它会在 xml 的末尾给我一个空组来插入一个属性，如果它不存在，用法看起来像

var replacer = new RegexReplacer("DisplayCustomerAttribute",
                 new Regex(@"(?:<customer\s.*?((\sdisplay=""(?:yes|no)"").*?|())>)"),
                 @" display=""yes""", 1)
 xmlString = replacer.ReplaceInString(xmlString);

作为旁注，这样做的原因是当值与默认值相同时，.net xml 序列化不包含属性。当您控制消费者时，这没关系，但在我们的情况下，我们不是，所以我们需要明确。