jobtrackingapp/JobTrackerApi/Services/CsvCellSafety.cs

using System.Globalization;
using System.Text;

namespace JobTrackerApi.Services;

public static class CsvCellSafety
{
    // Apply to text before CSV quoting, never to stored data or typed numbers/dates.
    // Prefix before (not instead of) whitespace/controls; an existing apostrophe is safe.
    public static string SpreadsheetText(string? value)
    {
        if (string.IsNullOrEmpty(value)) return value ?? "";
        foreach (var rune in value.EnumerateRunes())
        {
            if (Rune.IsWhiteSpace(rune) || Rune.IsControl(rune) || Rune.GetUnicodeCategory(rune) == UnicodeCategory.Format)
                continue;
            return rune.Value is '=' or '+' or '-' or '@' ? "'" + value : value;
        }
        return value;
    }
}