Pillole video 16

public static partial class StringExtensions
{
    public static string FirstUpper(this string str, bool OnlyFirst = false)
     => str switch
     {
         [] => string.Empty,
         [char single] => char.ToUpperInvariant(single).ToString(),
         [char first, .. var rest] => char.ToUpperInvariant(first) + (OnlyFirst ? rest.ToLowerInvariant() : rest)
     };

    public static string AllFirstUpper(this string str, bool OnlyFirst = false)
                    => string.Join(' ', str.Split(' ', StringSplitOptions.RemoveEmptyEntries).Select(e => e.FirstUpper(OnlyFirst)));

    public static string? EmptyToNull(this string str)
            => string.IsNullOrWhiteSpace(str) ? null : str;

    public static string OnlyNumbers(this string str)
     => new([.. str.Where(c => c >= '0' && c <= '9')]);

    public static string RemoveSpaces(this string str)
            => new([.. str.Where(c => c != ' ')]);

    [return: NotNullIfNotNull(nameof(str))]
    public static string GetValueOrDefault(this string? str, string defaultValue, bool whiteSpaceAsEmpty = false)
            => whiteSpaceAsEmpty ?
                 (string.IsNullOrWhiteSpace(str) ? defaultValue : str) :
                 (string.IsNullOrEmpty(str) ? defaultValue : str);

    public static bool IsEmail(this string value)
            => EmailRegEx().Match(value).Success;

    [GeneratedRegex("^([\\w-\\.]+)@((\\[[0-9]{1,3}\\.[0-9]{1,3}\\.[0-9]{1,3}\\.)|(([\\w-]+\\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\\]?)$")]
    private static partial Regex EmailRegEx();
}