CODEWITHSUNDEEP
c#regexwinforms
Oztaco
Oztaco

Reputation: 3459

Using regular expressions to check for a minimum number of characters?

I have the following code to validate usernames for an application:

Regex usernameRegex = new Regex("[A-Za-z0-9_]");
if (usernameRegex.IsMatch(MyTextBox.Text)) {
    // Create account, etc.
}

How would I modify my regular expression to check if the username has a certain number of characters?

Upvotes: 0

Views: 3109

Answers (3)

Nikson Kanti Paul
Nikson Kanti Paul

Reputation: 3440

This expression validates only all text which contains any combination of A to Z, a to z and number 0 to 9. You can define the length of the string using the regex: 

Regex reg= new Regex(@"^[A-Z]{3,}[a-z]{2,}\d*$")

{3,} and {2,} mean here that the string must have at least 3 capital characters, at least 2 small characters, and any amount of digit characters.

For example : Valid : AAAbb, AAAbb2, AAAAAAbbbbb, AAAAAbbbbbb4343434

Invalid: AAb, Abb, AbAbabA, 1AAAbb,

Upvotes: 1

Desolator
Desolator

Reputation: 22749

[A-Za-z0-9_]

[] "brackets": are a group of characters you want to match.

A-Z: means it will match any alphabet capitalized within this range A-Z.

a-z: means it will match any small alphabet within this range a-z.

0-9: means it will match any digit in this range 0-9.

_: means it will match the "_" character.

now this regex will usually match the following: any character from a to z (small, capital), any number (from 0-9) and the underscore "_".

i.e. "a.,.B.,10.._" this will match "a, B, 10, _". but of course you need to add the singleline regex option.

Upvotes: 0

Soviut
Soviut

Reputation: 91525

To set a minimum (or maximum) range in a regular expression you can use the {from,to} syntax.

The following will only match a string with a minimum of 5 alpha numeric and underscore characters:

[A-Za-z0-9_]{5,}

And the following will match a minimum of 5 and maximum of 10:

[A-Za-z0-9_]{5,10}

Upvotes: 0

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