CODEWITHSUNDEEP
regex
Dysnomian
Dysnomian

Reputation: 47

Check input has at least 5 digits while allowing other specific characters

I have a regular expression (@"[0-9\. \-\*\(\)]*") to allow only certain characters in my string. I want to know how I can also check that the string contains at least 5 of a subset of those characters namely [0-9].

I could use @"[0-9]{5,}" but this wouldn't allow for the other characters I want allowed in the input.

I could use @"[0-9\. \-\*\(\)]{5,}" but this would allow inputs that don't contain 5 digits.

I could use @"[0-9]{5,}[0-9\. \-\*\(\)]*" but this would require the 5 digits to be at the beginning of the input.

How can I check my input has at least 5 digits while still allowing other characters?

--

For example, I want to match:

12345 or 123 4-5

but not

1 3-5 or *- 4--*.

Upvotes: 1

Views: 452

Answers (1)

NetMage
NetMage

Reputation: 26907

Most characters are not special in a character group, so you don't need to escape them.

@"[0-9. *()-]{5,}(?<=([. *()-]*[0-9][. *()-]*){5,})";

This pattern says find a string of at least five valid characters, then verify the end of that string is preceded by a string of valid characters containing at least 5 digits.

I assume there was a reason your original expression didn't restrict the match to the whole string (locating the phone number?) but if you need the whole string to match:

@"^(?=(.*[0-9].*){5})[0-9. *()-]{5,}$"

This is somewhat simpler - check the string has at least 5 digits and consists only of valid characters. If you need to include the empty string, it would need a change.

If you are trying to validate phone numbers, both expressions are too simple, as they will accept strings like ((())12--33--44.

Upvotes: 2

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