How Can I Perform Case-Insensitive String Comparisons in C# While Ignoring Accented Characters?

Case-Insensitive String Comparison in C# Ignoring Accents

C# string comparisons often require ignoring both case and accent marks. Standard options like StringComparison.InvariantCultureIgnoreCase or StringComparison.OrdinalIgnoreCase don't handle accented characters appropriately. This necessitates a custom solution for accurate comparisons.

Removing Diacritics (Accents)

The following function efficiently removes diacritics from strings:

<code class="language-csharp">static string RemoveAccents(string text)
{
    string normalized = text.Normalize(NormalizationForm.FormD);
    StringBuilder sb = new StringBuilder();

    foreach (char c in normalized)
    {
        if (CharUnicodeInfo.GetUnicodeCategory(c) != UnicodeCategory.NonSpacingMark)
        {
            sb.Append(c);
        }
    }

    return sb.ToString().Normalize(NormalizationForm.FormC);
}</code>

This function:

1. Normalizes: Converts the input string to NormalizationForm.FormD, separating base characters and diacritics.
2. Filters: Iterates through the characters, appending only those that aren't non-spacing marks (accents).
3. Re-normalizes: Applies NormalizationForm.FormC for final cleanup.

Implementing Case-Insensitive Comparison

To compare strings while ignoring case and accents, use RemoveAccents and ToLowerInvariant() before comparison:

<code class="language-csharp">string str1 = "Héllo";
string str2 = "Hello";

if (RemoveAccents(str1).ToLowerInvariant() == RemoveAccents(str2).ToLowerInvariant())
{
    // Strings are equal (ignoring case and accents)
}</code>

This ensures a robust comparison that treats "Héllo" and "Hello" as identical. This method provides a flexible and accurate solution for case and accent-insensitive string comparisons in C#.

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