用一个唯一值替换字符串中的每个单词的实例

Question

在一个字符串中，我试图用不同的值更新同一单词的多个实例。

这是一个过于简单的例子，但鉴于以下字符串：

"The first car I saw was color, the second car was color and the third car was color" 

字的颜色我想用“红”，二审应该是“绿色”和更换的第一个实例第三例应该是“蓝色”。

我想要尝试的是寻找绑定单词的正则表达式模式，通过循环进行交互并逐个替换它们。请参阅下面的示例代码。

var colors = new List<string>{ "reg", "green", "blue" }; 
var sentence = "The first car I saw was color, the second car was color and the third car was color"; 

foreach(var color in colors) 
{ 
    var regex = new Regex("(\b[color]+\b)"); 
    sentence = regex.Replace(sentence, color, 1); 
} 

但是，“颜色”一词永远不会被替换为适当的颜色名称。我找不到我做错了什么。

Answer 1

试试比赛代表。

这是Regex.Replace（）的一个重载，大多数人都错过了。它只是让你定义一个潜在的上下文敏感的动态处理程序，而不是硬编码的字符串来代替，并且可能有副作用。 “i ++％”是一个模运算符，下面用它来简单循环访问这些值。你可以使用数据库或哈希表或任何东西。

var colors = new List<string> { "red", "green", "blue" }; 
var sentence = "The first car I saw was color, the second car was color and the third car was color"; 
int i = 0; 
Regex.Replace(sentence, @"\bcolor\b", (m) => { return colors[i++ % colors.Count]; }) 

该解决方案适用于任意数量的替换，这是更典型的替换（全局替换）。

Answer 2

我尽量远离正则表达式。它有它的地方，但不是简单的情况下，像这样恕我直言:)

public static class StringHelpers 
{ 
    //Copied from http://stackoverflow.com/questions/141045/how-do-i-replace-the-first-instance-of-a-string-in-net/141076#141076 
    public static string ReplaceFirst(this string text, string search, string replace) 
    { 
     int pos = text.IndexOf(search); 
     if (pos < 0) 
     { 
      return text; 
     } 
     return text.Substring(0, pos) + replace + text.Substring(pos + search.Length); 
    } 
} 


var colors = new List<string>{ "red", "green", "blue" }; 
string sentence = colors.Aggregate(
    seed: "The first car I saw was color, the second car was color and the third car was color", 
    func: (agg, color) => agg.ReplaceFirst("color", color)); 

Answer 3

的问题是，在你的榜样，color并不总是前面和后面一个非单词字符。为了您的例如，这个工作对我来说：

var regex = new Regex("\b?(color)\b?"); 

所以这样的：

var colors = new List<string>{ "red", "green", "blue" }; 
var sentence = "The first car I saw was color, the second car was color and the third car was color"; 

foreach(var color in colors) 
{ 
    var regex = new Regex("\b?(color)\b?"); 
    sentence = regex.Replace(sentence, color, 1); 
} 

产生以下：

第一辆车我看到的是红色的，第二辆车是绿和第三个 车是蓝色的