Need to a custom Regular expression for model based validation MVC

Question

I am using MVC.net 4 to build a web application. I need to regular expression for password to satisfy following conditions:

Must be between 6-32 characters long.
Must contain at least one lower case letter.
Must contain at least one upper case letter.
Must contain at least one numeric or special character.

Be careful about 4th point, I just need to expression of or condition between numeric and special character(not with and case for number and special character).

i am using following code that is working fine but need to use or case between Numeric and symbols.

[Required(ErrorMessage = "New Password is Required")]
[StringLength(32, MinimumLength = 6, ErrorMessage = "New Password should not be lessthan 6 character.")]
[RegularExpression(@"(?=.*[a-zA-Z0-9])(?=.*[~!@#$%^&*])[a-zA-Z0-9~!@#$%^&*]{8,15}", ErrorMessage = "Password should contain atleast one upper and lower character and on digit or special character.")]
public string NewPassword { get; set; }

i.e. I just need to password Expression as if set amanDeep1 then no need to check for symbol or if set as @amanDeep then no need to check for numeric values.

Wiktor Stribiżew · Accepted Answer · 2016-08-10 09:22:17Z

1

You put digits as part of the character class in the first lookahead, and the whole regex is not actually working as you need.

Put the 0-9 to the special chars lookahead requirement, and split the first lookahead to require at least 1 lower AND at least 1 upper case letter:

(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9~!@#$%^&*])[a-zA-Z0-9~!@#$%^&*]+
^^^^^^^^^^^^^^^^^^^^^^      ^^^                               ^

Note you can just use + at the end, since the length is restricted with the [StringLength(32, MinimumLength = 6, ErrorMessage = "New Password should not be lessthan 6 character.")].

Pattern details:

No anchors are used since the pattern inside a RegularExpressionAttribute is anchored by default
(?=.*[a-z]) - requires 1 lowercase ASCII letter
(?=.*[A-Z]) - requires 1 uppercase ASCII letter
(?=.*[0-9~!@#$%^&*]) - requires 1 digit or special char from the set (NOTE that the OR relationship is default between the chars/ranges inside a positive character class)
[a-zA-Z0-9~!@#$%^&*]+ - 1 or more chars from the set

edited Aug 10, 2016 at 9:22

answered Aug 10, 2016 at 7:54

Wiktor Stribiżew

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7 Comments

Amandeep Singh Over a year ago

Stribizew thanks for reply. This expression is using only 2 cases like if i enter aA then it is not requiring for symbol or number. But i need must to use Aa1 or Aa@ this kind of expression.

Amandeep Singh Over a year ago

Like amanDeep1 or AMandeep@ any number of symbols and charters more than six but at least 1 upper case Must, One lower case Must, One digit or Symbol are optional. Means password my contain must either one symbol or digit. But if digit entered no need to check for Symbol and vise versa.

Wiktor Stribiżew Over a year ago

Here is the demo of how this regex works: regex101.com/r/nU5mJ6/1. It matches the two values you supplied.

Amandeep Singh Over a year ago

Thanks @Stribizew. But its also working fine in case of amanDeee Amandeep and not requiring symbol or digit. It must requires a digit or symbol. Link is regex101.com/r/nU5mJ6/3 In this case it should match.

Amandeep Singh Over a year ago

Yea its working fine as per my requirements. Thank you very much @Wiktor Stribizew.... Thanks a lot.

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