How to ignore case in String.replace

Question

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"; 

How to replace 'camel' in sentence with 'horse' despite of string.Replace doesn't support ignoreCase on left string?

Answer 1

Use a regular expression:

var regex = new Regex( "camel", RegexOptions.IgnoreCase ); var newSentence = regex.Replace( sentence, "horse" ); 

Of course, this will also match words containing camel, but it's not clear if you want that or not.

If you need exact matches you can use a custom 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 );     } }  

Used with the previous example to wrap the match in a span as:

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 ) ); } 

Answer 2

Add an extension method for string to do the trick:

Usage:

string yourString = "TEXTTOREPLACE"; yourString.Replace("texttoreplace", "Look, I Got Replaced!", StringComparison.OrdinalIgnoreCase); 

Code:

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;     } }