Ignoring accented letters in string comparison

I need to compare 2 strings in C# and treat accented letters the same as non-accented letters. For example:

string s1 = "hello";
string s2 = "héllo";

s1.Equals(s2, StringComparison.InvariantCultureIgnoreCase);
s1.Equals(s2, StringComparison.OrdinalIgnoreCase);

These 2 strings need to be the same (as far as my application is concerned), but both of these statements evaluate to false. Is there a way in C# to do this?

From stackoverflow

• try this overload on the String.Compare Method.

  String.Compare Method (String, String, Boolean, CultureInfo)

  It produces a int value based on the compare operations including cultureinfo. the example in the page compares "Change" in en-US and en-CZ. CH in en-CZ is a single "letter".

  example from the link

  using System;
  using System.Globalization;
  
  class Sample {
      public static void Main() {
      String str1 = "change";
      String str2 = "dollar";
      String relation = null;
  
      relation = symbol( String.Compare(str1, str2, false, new CultureInfo("en-US")) );
      Console.WriteLine("For en-US: {0} {1} {2}", str1, relation, str2);
  
      relation = symbol( String.Compare(str1, str2, false, new CultureInfo("cs-CZ")) );
      Console.WriteLine("For cs-CZ: {0} {1} {2}", str1, relation, str2);
      }
  
      private static String symbol(int r) {
      String s = "=";
      if      (r < 0) s = "<";
      else if (r > 0) s = ">";
      return s;
      }
  }
  /*
  This example produces the following results.
  For en-US: change < dollar
  For cs-CZ: change > dollar
  */
  

  therefor for accented languages you will need to get the culture then test the strings based on that.

  http://msdn.microsoft.com/en-us/library/hyxc48dt.aspx

• The following method CompareIgnoreAccents(...) works on your example data. Here is the article where I got my background information: http://www.codeproject.com/KB/cs/EncodingAccents.aspx

  private static bool CompareIgnoreAccents(string s1, string s2)
  {
      return string.Compare(
          RemoveAccents(s1), RemoveAccents(s2), StringComparison.InvariantCultureIgnoreCase) == 0;
  }
  
  private static string RemoveAccents(string s)
  {
      Encoding destEncoding = Encoding.GetEncoding("iso-8859-8");
  
      return destEncoding.GetString(
          Encoding.Convert(Encoding.UTF8, destEncoding, Encoding.UTF8.GetBytes(s)));
  }
  

  I think an extension method would be better:

  public static string RemoveAccents(this string s)
  {
      Encoding destEncoding = Encoding.GetEncoding("iso-8859-8");
  
      return destEncoding.GetString(
          Encoding.Convert(Encoding.UTF8, destEncoding, Encoding.UTF8.GetBytes(s)));
  }
  

  Then the use would be this:

  if(string.Compare(s1.RemoveAccents(), s2.RemoveAccents(), true) == 0) {
     ...
  

• Write a method normalize(String s) that takes in a string and turns accented letters into non accented one. Then instead of comparing string x to string y, compare normalize(string x) to normalize(string y).

• Here's a function that strips diacritics from a string:

  static string RemoveDiacritics(string sIn)
  {
    string sFormD = sIn.Normalize(NormalizationForm.FormD);
    StringBuilder sb = new StringBuilder();
  
    foreach (char ch in sFormD)
    {
      UnicodeCategory uc = CharUnicodeInfo.GetUnicodeCategory(ch);
      if (uc != UnicodeCategory.NonSpacingMark)
      {
        sb.Append(ch);
      }
    }
  
    return (sb.ToString().Normalize(NormalizationForm.FormC));
  }
  

  More details here.

  The principle is that is it turns 'é' into 2 successive chars 'e', acute. It then iterates through the chars and skips the diacritics.

  "héllo" becomes "he<acute>llo", which in turn becomes "hello".

  Debug.Assert("hello"==RemoveDiacritics("héllo"));
  

  This line doesn't assert, which is what you want.