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Removing Diacritics from Strings

, 25 Jun 2012 CPOL
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When you search for matching substrings, you may have noticed that Google matches accented characters to unaccented. If you are searching strings which may contain accented characters, you should consider doing the same.

Introduction

One of the problems I encountered a while ago was that when searching text, "A" will not match "À", or "Á" or "Ä" or "Â" or indeed any other characters which include diacritics (which is the printers term for the little accent marks which sit above some characters in many languages). This means that the same text as entered by a native German speaker will not match the text entered by a native English speaker. This can be a pain, and limit the usefulness of the search.

I was reminded of this when I answered a QA question on writing a regex to cope with international names...

Background

I did not write this code; this code is taken (as described in the code comments) from Micheal Kaplans Blog - all I did was respace it and convert it to an extension method. However, I felt this needed a wider audience than it was getting, and should be where it gets searched more easily.

I am not going to try to describe how it works, as the original blog does that in more detail than I'd want to go into! (And probably a lot more accuracy...Sigh | :sigh: )

Using the Code

Include the code in a static class of your own, or download the source and add it to your project.

/// <summary>
/// Remove Diacritics from a string
/// This converts accented characters to nonaccented, which means it is
/// easier to search for matching data with or without such accents.
/// This code from Micheal Kaplans Blog:
///    http://blogs.msdn.com/b/michkap/archive/2007/05/14/2629747.aspx
/// Respaced and converted to an Extension Method
/// <example>
///    aàáâãäåçc
/// is converted to
///    aaaaaaacc
/// </example>
/// </summary>
/// <param name="s"></param>
/// <returns></returns>
public static String RemoveDiacritics(this String s)
    {
    String normalizedString = s.Normalize(NormalizationForm.FormD);
    StringBuilder stringBuilder = new StringBuilder();
 
    for (int i = 0; i < normalizedString.Length; i++)
        {
        Char c = normalizedString[i];
        if (CharUnicodeInfo.GetUnicodeCategory(c) != UnicodeCategory.NonSpacingMark)
            {
            stringBuilder.Append(c);
            }
        }
 
    return stringBuilder.ToString().Normalize(NormalizationForm.FormC);
    }

You can then use the method as you would any string extension method:

            string match = tbUserInput.Text.ToLower().RemoveDiacritics();
            if (string.IsNullOrWhiteSpace(match))
                {
                ...
                }

History

  • Original version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

OriginalGriff
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Comments and Discussions

 
QuestionMy vote of 5 Pinmemberhartpa28-Jan-14 19:17 
GeneralMy vote of 5 PinmemberBernard Chayer16-Mar-13 7:20 
GeneralMy vote of 5 PinmemberMatthew Searles5-Jul-12 17:29 
SuggestionWhile it is technically correct, it may still fail... PinmemberAndreas Gieriet27-Jun-12 0:35 

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