仅使用Regex替换某些组

Question

我们假设我有以下正则表达式:

-(\d+)-

我想更换,使用C#,1组(\d+)同AA,获得:

-AA-

现在我用以下方法替换它:

var text = "example-123-example";
var pattern = @"-(\d+)-";
var replaced = Regex.Replace(text, pattern, "-AA-"); 

但我真的不喜欢这个,因为如果我改变模式来匹配_(\d+)_,我也必须改变替换字符串_AA_,这是违反DRY原则的.

我正在寻找类似的东西:

保持匹配的文本的确切方式,但更改组1 this text和组2 another text...

编辑:
这只是一个例子.我只是在寻找一种做我上面所说的通用方法.

它应该适用于:

anything(\d+)more_text 以及你能想象到的任何模式.

我想要做的只是替换组,并保持匹配的其余部分.

Answer 1

一个好主意可能是将所有内容封装在组内,无论是否需要识别它们.这样你就可以在替换字符串中使用它们.例如:

var pattern = @"(-)(\d+)(-)";
var replaced = Regex.Replace(text, pattern, "$1AA$3"); 

或使用MatchEvaluator:

var replaced = Regex.Replace(text, pattern, m => m.Groups[1].Value + "AA" + m.Groups[3].Value);

另一种方式,略显凌乱,可能是使用lookbehind/lookahead:

(?<=-)(\d+)(?=-)

Answer 2

你可以使用lookahead和lookbehind来做到这一点:

var pattern = @"(?<=-)\d+(?=-)";
var replaced = Regex.Replace(text, pattern, "AA"); 

Answer 3

我也需要这个,我为它创建了以下扩展方法:

public static class RegexExtensions
{
    public static string ReplaceGroup(
        this Regex regex, string input, string groupName, string replacement)
    {
        return regex.Replace(
            input,
            m =>
            {
                var group = m.Groups[groupName];
                var sb = new StringBuilder();
                var previousCaptureEnd = 0;
                foreach (var capture in group.Captures.Cast<Capture>())
                {
                    var currentCaptureEnd =
                        capture.Index + capture.Length - m.Index;
                    var currentCaptureLength =
                        capture.Index - m.Index - previousCaptureEnd;
                    sb.Append(
                        m.Value.Substring(
                            previousCaptureEnd, currentCaptureLength));
                    sb.Append(replacement);
                    previousCaptureEnd = currentCaptureEnd;
                }
                sb.Append(m.Value.Substring(previousCaptureEnd));

                return sb.ToString();
            });
    }
}

用法:

var input = @"[assembly: AssemblyFileVersion(""2.0.3.0"")][assembly: AssemblyFileVersion(""2.0.3.0"")]";
var regex = new Regex(@"AssemblyFileVersion\(""(?<version>(\d+\.?){4})""\)");


var result = regex.ReplaceGroup(input , "version", "1.2.3");

结果:

[assembly: AssemblyFileVersion("1.2.3")][assembly: AssemblyFileVersion("1.2.3")]

Answer 4

如果您不想更改模式,可以使用匹配组的"组索引"和"长度"属性.

var text = "example-123-example";
var pattern = @"-(\d+)-";
var regex = new RegEx(pattern);
var match = regex.Match(text);

var firstPart = text.Substring(0,match.Groups[1].Index);    
var secondPart = text.Substring(match.Groups[1].Index + match.Groups[1].Length);
var fullReplace = firstPart + "AA" + secondPart;

Answer 5

这是另一个不错的清洁选项，不需要更改您的模式。

        var text = "example-123-example";
        var pattern = @"-(\d+)-";

        var replaced = Regex.Replace(text, pattern, (_match) =>
        {
            Group group = _match.Groups[1];
            string replace = "AA";
            return String.Format("{0}{1}{2}", _match.Value.Substring(0, group.Index - _match.Index), replace, _match.Value.Substring(group.Index - _match.Index + group.Length));
        });