CODEWITHSUNDEEP
c#.netregex
theateist
theateist

Reputation: 14399

How to write regex expression?

EDITED

How to write regex that will check if string's length is 8 or more and it contains only digits then it should contain at least one alphabetical character. For example:

  1. 1234567 - valid
  2. 1234a5678 - valid
  3. 12345678 - NOT valid because it's length is 8 and it doesn't contain any alphabetic

Upvotes: 1

Views: 226

Answers (5)

davioooh
davioooh

Reputation: 24676

If you are using c#, you can simplify your life and use two separate regex:

bool res = false;
string str = // your string
if (str < 8) 
{
    res = Regex.IsMatch(str, @"^[0-9]+$");
}
else 
{
    res = Regex.IsMatch(str, @"^(?=[a-zA-Z0-9]*[a-zA-Z])[a-zA-Z0-9]*$");
}

Upvotes: 0

Ria
Ria

Reputation: 10347

try this Regex:

^(\d{0,7}|(\d*[a-zA-Z]\d*)+)$

and your code can like this:

var str = new List<string> {"1234567", "1234a5678", "12345678"};
foreach (string s in str)
{
    var isValid = Regex.IsMatch(s, @"^(\d{0,7}|(\d*[a-zA-Z]\d*)+)$");
}

Upvotes: 0

Joey
Joey

Reputation: 354546

Because the question changed my initial regex solution wouldn't work anymore. In fact, it's hard to do with a single regex now. So another option:

bool Validate(string s) {
    int numDigits = s.Count(c => char.IsNumber(c));
    if (numDigits <= 7) {
        return numDigits == s.Length;
    } else {
        int numLetters = s.Count(c => char.IsLetter(c));
        return numLetters > 0 && numDigits + numLetters == s.Length;
    }
}

Upvotes: 1

ipavlic
ipavlic

Reputation: 4966

int Digits(string input) {
{
   int count = 0;
   foreach (char c in str)
   {
      if (c > '0' && c < '9')
          count++;
   }
   return count;
}

bool IsValid(string input)
{
    if (Digits(input) <= 8) {
        // is numeric
        return Regex.IsMatch(input, @"^[0-9]+$");
    }
    else {
        // has alpha && is alpha-numeric
        return Regex.IsMatch(input, @"[a-zA-Z]+") && Regex.IsMatch(input, @"^[0-9a-zA-Z]+$");
    }
}

Upvotes: 0

Dark
Dark

Reputation: 515

If you want to create & test your regex, don't hesitate to use this regex.powertoy.org

Upvotes: 0

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