How to create a url- and seo-friendly string in C# (text to slug generator)

1public static class StringHelper
2{
3    /// <summary>
4    /// Creates a URL And SEO friendly slug
5    /// </summary>
6    /// <param name="text">Text to slugify</param>
7    /// <param name="maxLength">Max length of slug</param>
8    /// <returns>URL and SEO friendly string</returns>
9    public static string UrlFriendly(string text, int maxLength = 0)
10    {
11        // Return empty value if text is null
12        if (text == null) return "";
13
14        var normalizedString = text
15            // Make lowercase
16            .ToLowerInvariant()
17            // Normalize the text
18            .Normalize(NormalizationForm.FormD);
19
20        var stringBuilder = new StringBuilder();
21        var stringLength = normalizedString.Length;
22        var prevdash = false;
23        var trueLength = 0;
24
25        char c;
26
27        for (int i = 0; i < stringLength; i++)
28        {
29            c = normalizedString[i];
30
31            switch (CharUnicodeInfo.GetUnicodeCategory(c))
32            {
33                // Check if the character is a letter or a digit if the character is a
34                // international character remap it to an ascii valid character
35                case UnicodeCategory.LowercaseLetter:
36                case UnicodeCategory.UppercaseLetter:
37                case UnicodeCategory.DecimalDigitNumber:
38                    if (c < 128)
39                        stringBuilder.Append(c);
40                    else
41                        stringBuilder.Append(ConstHelper.RemapInternationalCharToAscii(c));
42
43                    prevdash = false;
44                    trueLength = stringBuilder.Length;
45                    break;
46
47                // Check if the character is to be replaced by a hyphen but only if the last character wasn't
48                case UnicodeCategory.SpaceSeparator:
49                case UnicodeCategory.ConnectorPunctuation:
50                case UnicodeCategory.DashPunctuation:
51                case UnicodeCategory.OtherPunctuation:
52                case UnicodeCategory.MathSymbol:
53                    if (!prevdash)
54                    {
55                        stringBuilder.Append('-');
56                        prevdash = true;
57                        trueLength = stringBuilder.Length;
58                    }
59                    break;
60            }
61
62            // If we are at max length, stop parsing
63            if (maxLength > 0 && trueLength >= maxLength)
64                break;
65        }
66
67        // Trim excess hyphens
68        var result = stringBuilder.ToString().Trim('-');
69
70        // Remove any excess character to meet maxlength criteria
71        return maxLength <= 0 || result.Length <= maxLength ? result : result.Substring(0, maxLength);
72    }
73}
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1public static class ConstHelper
2{
3    /// <summary>
4    /// Remaps international characters to ascii compatible ones
5    /// based of: https://meta.stackexchange.com/questions/7435/non-us-ascii-characters-dropped-from-full-profile-url/7696#7696
6    /// </summary>
7    /// <param name="c">Charcter to remap</param>
8    /// <returns>Remapped character</returns>
9    public static string RemapInternationalCharToAscii(char c)
10    {
11        string s = c.ToString().ToLowerInvariant();
12        if ("àåáâäãåą".Contains(s))
13        {
14            return "a";
15        }
16        else if ("èéêëę".Contains(s))
17        {
18            return "e";
19        }
20        else if ("ìíîïı".Contains(s))
21        {
22            return "i";
23        }
24        else if ("òóôõöøőð".Contains(s))
25        {
26            return "o";
27        }
28        else if ("ùúûüŭů".Contains(s))
29        {
30            return "u";
31        }
32        else if ("çćčĉ".Contains(s))
33        {
34            return "c";
35        }
36        else if ("żźž".Contains(s))
37        {
38            return "z";
39        }
40        else if ("śşšŝ".Contains(s))
41        {
42            return "s";
43        }
44        else if ("ñń".Contains(s))
45        {
46            return "n";
47        }
48        else if ("ýÿ".Contains(s))
49        {
50            return "y";
51        }
52        else if ("ğĝ".Contains(s))
53        {
54            return "g";
55        }
56        else if (c == 'ř')
57        {
58            return "r";
59        }
60        else if (c == 'ł')
61        {
62            return "l";
63        }
64        else if (c == 'đ')
65        {
66            return "d";
67        }
68        else if (c == 'ß')
69        {
70            return "ss";
71        }
72        else if (c == 'þ')
73        {
74            return "th";
75        }
76        else if (c == 'ĥ')
77        {
78            return "h";
79        }
80        else if (c == 'ĵ')
81        {
82            return "j";
83        }
84        else
85        {
86            return "";
87        }
88    }
89}
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1const string text = "ICH MUß EINIGE CRÈME BRÛLÉE HABEN";
2Console.WriteLine(StringHelper.URLFriendly(text));
3// Output: 
4// ich-muss-einige-creme-brulee-haben
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