string sentence = "We know it contains 'camel' word.";
// Camel can be in different cases:
string s1 = "CAMEL";
string s2 = "CaMEL";
string s3 = "CAMeL";
// ...
string s4 = "Camel";
// ...
string s5 = "camel";
尽管string.Replace 不支持左侧字符串上的ignoreCase，如何将句子中的“骆驼”替换为“马”？
【问题讨论】：
标签： c# string replace ignore-case
使用正则表达式：
var regex = new Regex( "camel", RegexOptions.IgnoreCase );
var newSentence = regex.Replace( sentence, "horse" );
当然，这也会匹配包含骆驼的单词，但不清楚你是否想要。
如果您需要完全匹配，您可以使用自定义 MatchEvaluator。
public static class Evaluators
{
public static string Wrap( Match m, string original, string format )
{
// doesn't match the entire string, otherwise it is a match
if (m.Length != original.Length)
{
// has a preceding letter or digit (i.e., not a real match).
if (m.Index != 0 && char.IsLetterOrDigit( original[m.Index - 1] ))
{
return m.Value;
}
// has a trailing letter or digit (i.e., not a real match).
if (m.Index + m.Length != original.Length && char.IsLetterOrDigit( original[m.Index + m.Length] ))
{
return m.Value;
}
}
// it is a match, apply the format
return string.Format( format, m.Value );
}
}
与前面的示例一起使用，将匹配项包装在一个跨度中：
var regex = new Regex( highlightedWord, RegexOptions.IgnoreCase );
foreach (var sentence in sentences)
{
var evaluator = new MatchEvaluator( match => Evaluators.Wrap( match, sentence, "<span class='red'>{0}</span>" ) );
Console.WriteLine( regex.Replace( sentence, evaluator ) );
}
【讨论】：
为字符串添加一个扩展方法来解决这个问题：
用法：
string yourString = "TEXTTOREPLACE";
yourString.Replace("texttoreplace", "Look, I Got Replaced!", StringComparison.OrdinalIgnoreCase);
代码：
using System;
using System.Collections.Generic;
using System.IO;
public static class Extensions
{
public static string Replace(this string source, string oldString, string newString, StringComparison comp)
{
int index = source.IndexOf(oldString, comp);
// Determine if we found a match
bool MatchFound = index >= 0;
if (MatchFound)
{
// Remove the old text
source = source.Remove(index, oldString.Length);
// Add the replacemenet text
source = source.Insert(index, newString);
}
// recurse for multiple instances of the name
if (source.IndexOf(oldString, comp) != -1)
{
source = Replace(source, oldString, newString, comp);
}
return source;
}
}
【讨论】：
source 中第一次出现的oldString，与核心Replace 不同
这是一个采用 StringComparison 的扩展方法，使用 string.IndexOf:
[Pure]
public static string Replace(this string source, string oldValue, string newValue, StringComparison comparisonType)
{
if (source.Length == 0 || oldValue.Length == 0)
return source;
var result = new System.Text.StringBuilder();
int startingPos = 0;
int nextMatch;
while ((nextMatch = source.IndexOf(oldValue, startingPos, comparisonType)) > -1)
{
result.Append(source, startingPos, nextMatch - startingPos);
result.Append(newValue);
startingPos = nextMatch + oldValue.Length;
}
result.Append(source, startingPos, source.Length - startingPos);
return result.ToString();
}
顺便说一句，这里还有一个类似的 Contains 方法，也采用 StringComparison：
[Pure]
public static bool Contains(this string source, string value, StringComparison comparisonType)
{
return source.IndexOf(value, comparisonType) >= 0;
}
一些测试：
[TestFixture]
public class ExternalTests
{
private static string[] TestReplace_args =
{
"ab/B/c/ac",
"HELLO World/Hello/Goodbye/Goodbye World",
"Hello World/world/there!/Hello there!",
"hello WoRlD/world/there!/hello there!",
"///",
"ab///ab",
"/ab/cd/",
"a|b|c|d|e|f/|//abcdef",
"a|b|c|d|e|f|/|/:/a:b:c:d:e:f:",
};
[Test, TestCaseSource("TestReplace_args")]
public void TestReplace(string teststring)
{
var split = teststring.Split("/");
var source = split[0];
var oldValue = split[1];
var newValue = split[2];
var result = split[3];
Assert.That(source.Replace(oldValue, newValue, StringComparison.OrdinalIgnoreCase), Is.EqualTo(result));
}
}
【讨论】：
这是我的扩展方法，它结合了Tom Beech's、sntbob's 的递归性，以及对ksun 指出的错误的更清晰的修复。
代码：
public static string Replace(this string source, string oldString,
string newString, StringComparison comparison)
{
int index = source.IndexOf(oldString, comparison);
while (index > -1)
{
source = source.Remove(index, oldString.Length);
source = source.Insert(index, newString);
index = source.IndexOf(oldString, index + newString.Length, comparison);
}
return source;
}
用法：
string source = "banana";
Console.WriteLine(source.Replace("AN", "banana", StringComparison.OrdinalIgnoreCase));
结果：
bbananabananaa
而且，如果您仍然希望递归性质是可选的：
代码：
public static string Replace(this string source, string oldString,
string newString, StringComparison comparison,
bool recursive = true)
{
int index = source.IndexOf(oldString, comparison);
while (index > -1)
{
source = source.Remove(index, oldString.Length);
source = source.Insert(index, newString);
if (!recursive)
{
return source;
}
index = source.IndexOf(oldString, index + newString.Length, comparison);
}
return source;
}
用法：
string source = "banana";
Console.WriteLine(source.Replace("AN", "banana", StringComparison.OrdinalIgnoreCase, false));
结果：
香蕉
【讨论】：
利用StringComparison，因为它方便OrdinalIgnoreCase
string sentence = "We know it contains 'camel' word.";
string wordToFind = "camel";
string replacementWord = "horse";
int index = sentence.IndexOf(wordToFind , StringComparison.OrdinalIgnoreCase)
// Did we match the word regardless of case
bool match = index >= 0;
// perform the replace on the matched word
if(match) {
sentence = sentence.Remove(index, wordToFind.Length)
sentence = sentence.Insert(index, replacementWord)
}
如果 C# String 类有像 Java 这样的 ignoreCase() 方法当然会很好。
【讨论】：
你也可以使用 String.IndexOf
http://msdn.microsoft.com/en-us/library/system.string.indexof.aspx
这样做可能会比使用 RegExpressions 获得更好的性能（我讨厌它们，因为它们不直观且容易搞砸，尽管这个简单的 .Net 函数调用抽象了实际混乱的 RegEx，并且不提供有很大的错误空间），但这可能不是你关心的问题；这些天电脑真的很快，对吧？ :) 采用 StringComparison 对象的 IndexOf 重载允许您有选择地忽略大小写，并且因为 IndexOf 从指定位置返回第一个匹配项，您必须编写一个循环来处理具有多个匹配项的字符串。
【讨论】：
public static string CustomReplace(string srcText, string toFind, string toReplace, bool matchCase, bool replace0nce)
{
StringComparison sc = StringComparison.OrdinalIgnoreCase;
if (matchCase)
sc = StringComparison.Ordinal;
int pos;
while ((pos = srcText.IndexOf(toFind, sc)) > -1)
{
srcText = srcText.Remove(pos, toFind.Length);
srcText = srcText.Insert(pos, toReplace);
if (replace0nce)
break;
}
return srcText;
}
【讨论】：
它可能没有其他一些答案那么有效，但我有点喜欢 sntbob 编写的 CustomReplace 函数。
但是，它有一个缺陷。如果文本替换是递归的，它将导致无限循环。例如，CustomReplace("I eat bananas!","an","banana",false,false) 会导致无限循环，字符串会继续变大。 例如，在第 4 次迭代之后，字符串将是“我吃 bbbbbananaanaanaanaanas！”
如果您只想替换“banana”中的两个“an”实例，那么您将不得不采取另一种方法。我修改了 sntbob 的代码来解决这种情况。我承认它更复杂，但它处理递归替换。
public static string CustomReplace(string srcText, string toFind, string toReplace, bool matchCase, bool replaceOnce)
{
StringComparison sc = StringComparison.OrdinalIgnoreCase;
if (matchCase)
sc = StringComparison.Ordinal;
int pos;
int previousProcessedLength = 0;
string alreadyProcessedTxt = "";
string remainingToProcessTxt = srcText;
while ((pos = remainingToProcessTxt.IndexOf(toFind, sc)) > -1)
{
previousProcessedLength = alreadyProcessedTxt.Length;
//Append processed text up until the end of the found string and perform replacement
alreadyProcessedTxt += remainingToProcessTxt.Substring(0, pos + toFind.Length);
alreadyProcessedTxt = alreadyProcessedTxt.Remove(previousProcessedLength + pos, toFind.Length);
alreadyProcessedTxt = alreadyProcessedTxt.Insert(previousProcessedLength + pos, toReplace);
//Remove processed text from remaining
remainingToProcessTxt = remainingToProcessTxt.Substring(pos + toFind.Length);
if (replaceOnce)
break;
}
return alreadyProcessedTxt + remainingToProcessTxt;
}
【讨论】：
为什么不直接导入 Microsoft.VisualBasic 命名空间并使用 VB Strings.Replace 方法？
https://msdn.microsoft.com/en-us/library/microsoft.visualbasic.strings.replace(v=vs.110).aspx
例如
var newString = Strings.Replace(SourceString, FindTextValue, ReplacementTextValue, 1, -1, Constants.vbTextCompare);
vbTextCompare 强制进行不区分大小写的替换。任务完成。
好吧，它不是“纯”C#，但它可以让您以更少的复杂性和混乱程度到达您想去的地方。
【讨论】：
这是使用 StringComparison 作为扩展方法的另一种选择。在 StringBuilder 对象上。我读过一些文章，表明 StringBuilder 在内存方面可能比使用字符串更有效。如果您需要的话，您可以轻松地将其更改为使用字符串。
/// <summary>
/// Extension method to find/replace replaces text in a StringBuilder object
/// </summary>
/// <param name="original">Source StringBuilder object</param>
/// <param name="oldString">String to search for</param>
/// <param name="newString">String to replace each occurrance of oldString</param>
/// <param name="stringComparison">String comparison to use</param>
/// <returns>Original Stringbuilder with replacements made</returns>
public static StringBuilder Replace(this StringBuilder original,
string oldString, string newString, StringComparison stringComparison)
{
//If anything is null, or oldString is blank, exit with original value
if ( newString == null || original == null || string.IsNullOrEmpty(oldString))
return original;
//Convert to a string and get starting position using
//IndexOf which allows us to use StringComparison.
int pos = original.ToString().IndexOf(oldString, 0, stringComparison);
//Loop through until we find and replace all matches
while ( pos >= 0 )
{
//Remove the old string and insert the new one.
original.Remove(pos, oldString.Length).Insert(pos, newString);
//Get the next match starting 1 character after last replacement (to avoid a possible infinite loop)
pos = original.ToString().IndexOf(oldString, pos + newString.Length + 1, stringComparison);
}
return original;
}
【讨论】：