Pihrtsoft.Text.RegularExpressions.Linq.Chars.Digit C# (CSharp) Method

        public static CharGrouping Digit() => Character(CharClass.Digit);

 /// <summary>
 /// Appends a pattern that matches a character from the digit character class.
 /// </summary>
 /// <returns></returns>
 public CharGrouping Digit() => Append(Chars.Digit());