Question

I need a regular expression for a password. The password has to contain at least 8 characters. At least one character must be a number or a special character (not a letter).

[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 8)]
[RegularExpression(@"(?=.*\W)?(?=.*\d)", ErrorMessage = "Error message")]
[DataType(DataType.Password)]
[Display(Name = "Password")]
public string Password { get; set; }

I have a length validation, but I need help with a regular expression that checks if the password contains at least one number or special character.

Examples of valid passwords:

testtest85*
testtes*
testtes1
test1234*+

Examples of not valid passwords:

testtest
testabc

Answer 1

Use regex pattern ^(?=.{8})(?=.*[^a-zA-Z])

---

Explanation:

^(?=.{8})(?=.*[^a-zA-Z])
│└──┬───┘└──────┬──────┘
│   │           │
│   │           └ string contains some non-letter character
│   │
│   └ string contains at least 8 characters
│
└ begining of line/string

---

If you want to limit also maximum length (let’s say 16), then use regex pattern:

^(?=.{8,16}$)(?=.*[^a-zA-Z])