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";
如何在句子中将“camel”替换为“horse”，尽管string.Replace不支持在左字符串上忽略大小写？
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camel的单词，但不清楚您是否需要。
如果您需要精确匹配，可以使用自定义的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 );
}
}
结合前面的示例，可以将匹配项包装在一个 span 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 ) );
}
为字符串添加一个扩展方法来完成这个技巧：
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;
}
}
source中第一个出现的oldString，与核心的Replace不同。 - bdukes这是一个扩展方法，使用字符串的IndexOf方法并带有StringComparison参数：
[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();
}
另外，这里还有一个类似的 Contains 方法，也可以接受 StringComparison 参数：
[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));
}
}
这是我的扩展方法，它结合了Tom Beech的方法和sntbob的递归方法，并对ksun指出的bug进行了修复。
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;
}
使用方法：
string source = "banana";
Console.WriteLine(source.Replace("AN", "banana", StringComparison.OrdinalIgnoreCase));
结果：
bbananabananaa
如果你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;
}
使用方法：
string source = "banana";
Console.WriteLine(source.Replace("AN", "banana", StringComparison.OrdinalIgnoreCase, false));
结果:
香蕉
使用StringComparison，因为它方便的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类有一个像Java一样的ignoreCase()方法就太好了。
http://msdn.microsoft.com/en-us/library/system.string.indexof.aspx
通过这种方式进行操作可能会比使用正则表达式获得略微更好的性能（我讨厌它们，因为它们不直观且容易出错，尽管这个简单的 .Net 函数调用抽象了实际混乱的正则表达式，并且提供了很少的错误空间），但这可能对您并不重要；现在计算机非常快，对吧？:) 采用接受 StringComparison 对象的 IndexOf 重载函数可以选择忽略大小写，由于 IndexOf 返回指定位置处的第一个匹配项，因此您需要编写一个循环来处理具有多个匹配项的字符串。虽然不如其他答案高效，但我还是挺喜欢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，在第四次迭代之后，字符串将变为"I eat bbbbbananaanaanaanaanas!"
如果你只想替换"banana"中的两个"an"实例，那么你需要采取另一种方法。我修改了sntbob的代码以解决这个问题。我承认这更加复杂，但它可以处理递归替换。
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;
}
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;
}
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);
这里还有一种使用StringComparison作为扩展方法的替代方案，它可以在StringBuilder对象上使用。我读过一些文章表明，相比于使用字符串，StringBuilder可能会更有效地利用内存。如果需要，您可以轻松地将其改为适用于字符串。
/// <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;
}