Question

在字符串中，我正在尝试使用不同的值更新同一个单词的多个实例。

这是一个过于简化的示例，但给出以下字符串：

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

我希望用“red”替换单词color的第一个实例，第二个实例应为“green”，第三个实例应为“blue”。

我想要尝试的是一个正则表达式模式来查找已绑定的单词，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”这个词永远不会被适当的颜色名称取代。我找不到我做错了什么。

Answer 1

尝试匹配委托。

大多数人都错过了Regex.Replace（）的重载。它只是让您定义一个潜在的上下文敏感的动态处理程序，而不是要替换的硬编码字符串，并且可能有副作用。＆＃34; i ++％＆＃34;下面使用模数运算符来简单地遍历值。您可以使用数据库或哈希表或任何其他内容。

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]; })

此解决方案适用于任意数量的替换，这是更典型的（全局替换）。

Answer 2

问题在于，在您的示例中，color并非始终以非单词字符开头和后跟。对于示例，这对我有用：

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

所以这个：

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);
}

产生这个：

我看到的第一辆车是红色的，第二辆车是绿色的，第三辆是车是蓝色的

Answer 3

我尽可能地远离正则表达式。它有它的位置，但不适用于像这样的简单情况恕我直言：）

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));

用唯一值替换字符串中单词的每个实例

3 个答案: