Structure because structure

Extensions/StringExtensions.cs

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+namespace Xorog.UniversalExtensions;
+
+public static class StringExtensions
+{
+    /// <summary>
+    /// Extensions for string.IsNullOrWhiteSpace
+    /// </summary>
+    /// <param name="str"></param>
+    /// <returns>Whether the string is null, empty or only contains whitespaces</returns>
+    public static bool IsNullOrWhiteSpace(this string str)
+        => string.IsNullOrWhiteSpace(str);
+
+    /// <summary>
+    /// Extensions for string.IsNullOrEmpty
+    /// </summary>
+    /// <param name="str"></param>
+    /// <returns>Whether the string is null or empty</returns>
+    public static bool IsNullOrEmpty(this string str)
+        => string.IsNullOrEmpty(str);
+
+    /// <summary>
+    /// Check if a string contains only digits
+    /// </summary>
+    /// <param name="str"></param>
+    /// <returns></returns>
+    public static bool IsDigitsOnly(this string str)
+    {
+        foreach (char c in str)
+        {
+            if (c is < '0' or > '9')
+                return false;
+        }
+
+        return true;
+    }
+
+    /// <summary>
+    /// Get all digits from a string
+    /// </summary>
+    /// <param name="str"></param>
+    /// <returns></returns>
+    public static string GetAllDigits(this string str) =>
+        new(str.Where(Char.IsDigit).ToArray());
+
+    /// <summary>
+    /// Get country flag emoji based on Iso Country Code
+    /// </summary>
+    /// <param name="country"></param>
+    /// <returns></returns>
+    public static string IsoCountryCodeToFlagEmoji(this string country)
+    {
+        return string.Concat(country.ToUpper().Select(x => char.ConvertFromUtf32(x + 0x1F1A5)));
+    }
+
+    /// <summary>
+    /// Shorten a string to the given length
+    /// </summary>
+    /// <param name="value"></param>
+    /// <param name="maxLength"></param>
+    /// <returns></returns>
+    public static string Truncate(this string value, int maxLength)
+    {
+        if (string.IsNullOrEmpty(value))
+            return value;
+        return value.Length <= maxLength ? value : value[..maxLength];
+    }
+
+    /// <summary>
+    /// Shorten a string to the given length and add ".." at the end
+    /// </summary>
+    /// <param name="value"></param>
+    /// <param name="maxLength"></param>
+    /// <returns></returns>
+    public static string TruncateWithIndication(this string value, int maxLength)
+    {
+        if (string.IsNullOrEmpty(value))
+            return value;
+
+        return value.Length <= maxLength ? value : $"{value[..(maxLength - 2)]}..";
+    }
+
+    /// <summary>
+    /// Remove unsupported characters from string to generate a valid filename
+    /// </summary>
+    /// <param name="name">The string with potentionally unwanted characters</param>
+    /// <param name="replace_char">The character the unwanted characters get replaced with (default: <code>_</code>)</param>
+    /// <returns>A valid filename</returns>
+    public static string MakeValidFileName(this string name, char replace_char = '_')
+    {
+        string invalidChars = System.Text.RegularExpressions.Regex.Escape(new string(System.IO.Path.GetInvalidFileNameChars()));
+        string invalidRegStr = string.Format(@"([{0}]*\.+$)|([{0}]+)", invalidChars);
+
+        return System.Text.RegularExpressions.Regex.Replace(name, invalidRegStr, replace_char.ToString()).Replace('&', replace_char);
+    }
+
+    /// <summary>
+    /// Changes the first letter to upper.
+    /// </summary>
+    /// <param name="str">The string to modify.</param>
+    /// <returns>The string with the first letter changed to upper.</returns>
+    public static string FirstLetterToUpper(this string str)
+    {
+        return $"{str.First().ToString().ToUpper()}{str.Remove(0, 1)}";
+    }
+}