[英]How to ignore case in String.replace
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";
如何與“馬”的句子替換“駱駝”盡管string.Replace
不支持ignoreCase
左弦?
使用正則表達式:
var regex = new Regex( "camel", RegexOptions.IgnoreCase );
var newSentence = regex.Replace( sentence, "horse" );
當然,這也會匹配包含駱駝的單詞,但是不清楚你是否想要這個。
如果您需要完全匹配,可以使用自定義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 );
}
}
與前一個示例一起使用以將匹配包裝在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 ) );
}
添加字符串的擴展方法來執行操作:
用法:
string yourString = "TEXTTOREPLACE";
yourString.Replace("texttoreplace", "Look, I Got Replaced!", StringComparison.OrdinalIgnoreCase);
碼:
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;
}
}
這是一個使用String.IndexOf的StringComparison的擴展方法:
[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();
}
順便說一句,這里也是一個類似的Contains方法,也采用了StringComparison:
[Pure]
public static bool Contains(this string source, string value, StringComparison comparisonType)
{
return source.IndexOf(value, comparisonType) >= 0;
}
一些測試:
[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));
}
}
這是我的擴展方法,它將Tom Beech與sntbob的遞歸結合起來, 並對ksun指出的bug進行了更清晰的修復。
碼:
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));
結果:
bbananabananaa
而且,如果您仍然希望遞歸性質是可選的:
碼:
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));
結果:
bbananaana
利用StringComparison
因為它方便的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類具有像Java這樣的ignoreCase()
方法,那肯定會很好。
您也可以使用String.IndexOf
http://msdn.microsoft.com/en-us/library/system.string.indexof.aspx
與RegExpressions相比,你可以通過這種方式獲得稍微好一點的表現(我厭惡它們,因為它們不直觀且容易搞砸,雖然這個簡單的.Net函數調用抽象了實際凌亂的RegEx,並沒有提供太多空間錯誤),但這可能不是你的問題; 這幾天電腦很快,對吧? :)采用StringComparison對象的IndexOf的重載允許您可選地忽略大小寫,並且因為IndexOf從指定位置返回第一個匹配項,所以您必須編寫一個循環來處理具有多個匹配項的字符串。
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;
}
它可能沒有其他一些答案那么高效,但我有點像sntbob編寫的CustomReplace函數。
但是,它有一個缺陷。 如果文本替換是遞歸的,則會導致無限循環。 例如,CustomReplace(“我吃香蕉!”,“一個”,“香蕉”,假,假)將導致無限循環,字符串將繼續變大。 例如,在第4次迭代之后,字符串將是“我吃bbbbbananaanaanaanaanas!”
如果你只想替換“香蕉”中的兩個“an”實例,那么你將不得不采取另一種方法。 我修改了sntbob的代碼來解釋這種情況。 我承認它更復雜,但它處理遞歸替換。
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;
}
這是使用StringComparison作為擴展方法的另一種替代方法。 在StringBuilder對象上。 我已經閱讀了一些文章,表明StringBuilder可能比使用字符串更有效。 如果您需要,可以輕松地將其更改為使用字符串。
/// <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;
}
為什么不直接導入Microsoft.VisualBasic命名空間並使用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強制不區分大小寫的替換。 任務完成。
好吧,它不是'純粹的'C#,但是它可以讓你到達你想去的地方,而且復雜程度更低,而且更糟糕。
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