using System;

using System.Text;

using System.Globalization;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        var input = "'";

        var result = RemoveDiacritics(input);

        Console.WriteLine(result);

    }

    private static string RemoveDiacritics(string text) 

    {

        if (string.IsNullOrWhiteSpace(text))

            return text;

​

        text = text.Normalize(NormalizationForm.FormD);

        var chars = text.Where(c => CharUnicodeInfo.GetUnicodeCategory(c) != UnicodeCategory.NonSpacingMark).ToArray();

        return new string(chars).Normalize(NormalizationForm.FormC);

    }

    private static Dictionary<string, string> foreign_characters = new Dictionary<string, string>

    {

        { "äæǽ", "ae" },

        { "öœ", "oe" },

        { "ü", "ue" },

        { "Ä", "Ae" },

        { "Ü", "Ue" },

        { "Ö", "Oe" },

        { "ÀÁÂÃÄÅǺĀĂĄǍΑΆẢẠẦẪẨẬẰẮẴẲẶА", "A" },

        { "àáâãåǻāăąǎªαάảạầấẫẩậằắẵẳặа", "a" },

        { "Б", "B" },

        { "б", "b" },

        { "ÇĆĈĊČ", "C" },

        { "çćĉċč", "c" },

        { "Д", "D" },

        { "д", "d" },

        { "ÐĎĐΔ", "Dj" },

        { "ðďđδ", "dj" },

        { "ÈÉÊËĒĔĖĘĚΕΈẼẺẸỀẾỄỂỆЕЭ", "E" },

        { "èéêëēĕėęěέεẽẻẹềếễểệеэ", "e" },

        { "Ф", "F" },

        { "ф", "f" },

        { "ĜĞĠĢΓГҐ", "G" },

        { "ĝğġģγгґ", "g" },

        { "ĤĦ", "H" },

        { "ĥħ", "h" },

        { "ÌÍÎÏĨĪĬǏĮİΗΉΊΙΪỈỊИЫ", "I" },

        { "ìíîïĩīĭǐįıηήίιϊỉịиыї", "i" },

        { "Ĵ", "J" },

        { "ĵ", "j" },

        { "ĶΚК", "K" },

        { "ķκк", "k" },

        { "ĹĻĽĿŁΛЛ", "L" },

        { "ĺļľŀłλл", "l" },

        { "М", "M" },

        { "м", "m" },

        { "ÑŃŅŇΝН", "N" },

        { "ñńņňʼnνн", "n" },

        { "ÒÓÔÕŌŎǑŐƠØǾΟΌΩΏỎỌỒỐỖỔỘỜỚỠỞỢО", "O" },

        { "òóôõōŏǒőơøǿºοόωώỏọồốỗổộờớỡởợо", "o" },

        { "П", "P" },

        { "п", "p" },

        { "ŔŖŘΡР", "R" },

        { "ŕŗřρр", "r" },

        { "ŚŜŞȘŠΣС", "S" },

        { "śŝşșšſσςс", "s" },

        { "ȚŢŤŦτТ", "T" },

        { "țţťŧт", "t" },

        { "ÙÚÛŨŪŬŮŰŲƯǓǕǗǙǛŨỦỤỪỨỮỬỰУ", "U" },

        { "ùúûũūŭůűųưǔǖǘǚǜυύϋủụừứữửựу", "u" },

        { "ÝŸŶΥΎΫỲỸỶỴЙ", "Y" },

        { "ýÿŷỳỹỷỵй", "y" },

        { "В", "V" },

        { "в", "v" },

        { "Ŵ", "W" },

        { "ŵ", "w" },

        { "ŹŻŽΖЗ", "Z" },

        { "źżžζз", "z" },

        { "ÆǼ", "AE" },

        { "ß", "ss" },

        { "IJ", "IJ" },

        { "ij", "ij" },

        { "Œ", "OE" },

        { "ƒ", "f" },

        { "ξ", "ks" },

        { "π", "p" },

        { "β", "v" },

        { "μ", "m" },

        { "ψ", "ps" },

        { "Ё", "Yo" },

        { "ё", "yo" },

        { "Є", "Ye" },

        { "є", "ye" },

        { "Ї", "Yi" },

        { "Ж", "Zh" },

        { "ж", "zh" },

        { "Х", "Kh" },

        { "х", "kh" },

        { "Ц", "Ts" },

        { "ц", "ts" },

        { "Ч", "Ch" },

        { "ч", "ch" },

        { "Ш", "Sh" },

        { "ш", "sh" },

        { "Щ", "Shch" },

        { "щ", "shch" },

        { "ЪъЬь", "" },

        { "Ю", "Yu" },

        { "ю", "yu" },

        { "Я", "Ya" },

        { "я", "ya" },

    };

​

    private static char RemoveDiacritics(this char c){

        foreach(KeyValuePair<string, string> entry in foreign_characters)

        {

            if(entry.Key.IndexOf (c) != -1)

            {

                return entry.Value[0];

            }

        }

        return c;

    }

​

    private static string RemoveDiacritics_v2(this string s) 

    {

        //StringBuilder sb = new StringBuilder ();

        string text = "";

​

​

        foreach (char c in s)

        {

            int len = text.Length;

​

            foreach(KeyValuePair<string, string> entry in foreign_characters)

            {

                if(entry.Key.IndexOf (c) != -1)

                {

                    text += entry.Value;

                    break;

                }

            }

​

            if (len == text.Length) {

                text += c;  

            }

        }

        return text;

    }

}

​

​