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How to get alphanumeric key from string?

C#  |  .NET

There is sometimes the necessity to generate an alphanumeric key from a string, such as to generate a part of the URL based on the article title. You need to make all letters lower-case and replace some language-specific characters, as well as replace all characters other than a-z and 0-9 with a dash. What's more, no more than one dash in a row is allowed. How to solve this problem?

The most important actions are performed in the following method:

string GetKey(string text)
    // Replace some language-specific characters.
    Dictionary replace = new()
        { 'ą', 'a' },
        { 'ć', 'c' },
        { 'ę', 'e' },
        { 'ł', 'l' },
        { 'ń', 'n' },
        { 'ó', 'o' },
        { 'ś', 's' },
        { 'ź', 'z' },
        { 'ż', 'z' }
    text = text.ToLower();
    foreach ((char from, char to) in replace) { text = text.Replace(from, to); }

    // Replace all not-supported characters with dashes.
    List supported = [];
    for (char c = 'a'; c <= 'z'; c++) { supported.Add(c); }
    for (char c = '0'; c <= '9'; c++) { supported.Add(c); }
    string key = string.Empty;
    foreach (char c in text) { key += supported.Contains(c) ? c : '-'; }

    // Remove multiple dashes, as well as dashes at the beginning or end.
    key = key.Replace("--", "-");
    key = key.Trim('-');
    return key;

To simplify testing, the Print auxiliary method is shown below:

void Print(string text)
    Console.Write(" -> ");

A few of its calls are presented as follows:

Print("Hello world!");
Print("Dzień dobry w przepięknej Polsce! :-)");
Print("I was born on 9.11.1988.");

If you run the code, you will get the following result:

Hello world! -> hello-world
Dzień dobry w przepięknej Polsce! :-) -> dzien-dobry-w-przepieknej-polsce
I was born on 9.11.1988. -> i-was-born-on-9-11-1988

The content, including any part of code, is presented without warranty, either express or implied. The author cannot be held liable for any damages caused or alleged to have been caused directly or indirectly by any content shown on this website.

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