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I am using Asp.Net/C#, I am using RegularExpressionValidator to match a password field.My requirement is that I need the user to enter a password which will be atleast 7 characters long and it can contain any combination of alphabets and numeric characters , however it should contain strictly one non-alphanumeric character , can anybody suggest me as to how I can achieve this. Any suggestions are welcome.Thank you

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3 Answers 3

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Try this

String[] words = { "Foobaar", "Foobar1", "1234567", "123Fooo", "Fo12!", "Foo12!", "Foobar123!", "!Foobar123", "Foo#bar123" };

foreach (String s in words) {

    Match word = Regex.Match(s, @"
          ^                        # Match the start of the string
            (?=                    # positive look ahead
                [\p{L}\p{Nd}]*     # 0 or more letters or digits at the start
                [^\p{L}\p{Nd}]     # string contains exactly one non-digit, non-letter
                [\p{L}\p{Nd}]*     # 0 or more letters or digits after the special character 
            $)                     # till the end of the string
            .{7,}                  # match 7 or more characters
          $                        # Match the end of the string
        ", RegexOptions.IgnorePatternWhitespace);
    if (word.Success) {
        Console.WriteLine(s + ": valid");
    }
    else {
        Console.WriteLine(s + ": invalid");
    }
}
Console.ReadLine();

\p{L} is a unicode code point with the property "letter"

\p{Nd} is a unicode code point with the property "digit"

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2 Comments

can I use this with an asp.net regularexpression validator
I don't know asp.net, but I tested it with c#, so since both is .net it should work.
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((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{7,20})


(           # Start of group
  (?=.*\d)      #   must contains one digit from 0-9
  (?=.*[a-z])       #   must contains one lowercase characters
  (?=.*[A-Z])       #   must contains one uppercase characters
  (?=.*[@#$%])      #   must contains one special symbols in the list "@#$%"
              .     #     match anything with previous condition checking
                {7,20}  #        length at least 7 characters and maximum of 20 
)

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11 Comments

can you suggest me to allow the user to enter only non aplhanumeric character
[^\w\d] regex should do it.
@freebird: You mean.. only 1 non-alphanumeric? I can edit the answer if that's what you need. Else, Jack's comment should do it.
@Jack i think it will words and digits , how do I include only one non alphanumeric character as well
@RobinMaben , I meant that it should contain words digits and only one nonalphanumeric character
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I used the following to match my needs ^([\w]*[(\W)]{1}[\d]*)$ , this allows a password to start with an alphabet any number of times , then the password must contain an non-alphanumeric character only 1 time , followed by a digits any number of times.

2 Comments

cool that you came up with an own solution. I assume that you do the length check then somewhere else. Some hints: {1} is superfluous, you simply don't need it, you don't need the round brackets inside a character class, when your char class has only one member you don't need a class, \w contains also the underscore and at last: you don't need the brackets around the whole expression. So you could simplify your expression to ^\w*\W\d*$
@Stema thanks a lot I will simplify the expression , My length check is done in the configuration file , the pattern I used in my answer will only allow passwords like abc@123 , xyz#456 etc.thanks

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