如何编写一个允许空格和限制字符数的正则表达式？

Question

I have some validation in my Model. For the Society Name:

1. Only Letters, Upper and Lower Case.
2. No numbers.
3. Must allow for Camel Case
4. Allow for Spaces between words.
5. Limited from 1-16 characters.

Code:

[Required(ErrorMessage = "Society Name is required.")]
    [StringLength(200, ErrorMessage = "The {0} has a maximum of {1} characters.")]
    [RegularExpression(@"^[A-Z][0-9]{16}$", ErrorMessage = "Society Name field requires 1-16 Alphabetical characters.")]
    [Display(Name = "Society Name *")]
    public string SocietyName { get; set; }

Answer 1

You should actually allow spaces and lowercase letters, right now, those patterns are not even present in your current regex. Also, you used [0-9] that matches digits, although numbers should not be matched as per your requirements.

To match lower- and uppercase letters or/and whitespace chars, you may use

^[A-Za-z\s]{1,16}$

See this regex demo .

Details

• ^ - start of string
• [A-Za-z\\s]{1,16} - 1 to 16 ASCII letters or/and whitespace chars
• $ - end of string.

If you only want to allow 1 space between words, use

^(?=.{1,16}$)[A-Za-z]+(?:\s[A-Za-z]+)*$

See this regex demo .

Details

• ^ - start of string
• (?=.{1,16}$) - the string length can be 1 to 16
• [A-Za-z]+ - 1+ ASCII letters
• (?:\\s[A-Za-z]+)* - zero or more repetitions of
  • \\s - 1 whitespace
  • [A-Za-z]+ - 1+ ASCII letters
• $ - end of string.