How to check the phone number using Regex-CodePudding

I am trying to check the user input, I want the phone number to be like 000-0000.

But my code here does not work as I want. I input

"123-4444444"

and it also matches.

I am not familiar with Regex, but I need to use it, so can you tell me how to change the pattern?

Regex regex = new Regex(@"\d{3}-\d{4}");
if (!(regex.IsMatch(txtUpdatePhoneNumber.Text)))
{
   MessageBox.Show("Phone number format should be 000-0000", "Error");
}

CodePudding user response：

You have to specify start and beginning

Please check the regex here: https://regex101.com/r/MZ4YPo/1

^: start of string
$: end of string

^\d{3}-\d{4}$

Regex regex = new Regex(@"^\d{3}-\d{4}$");
if (!(regex.IsMatch(txtUpdatePhoneNumber.Text)))
{
    MessageBox.Show("Phone number format should be 000-0000", "Error");
}

CodePudding user response：

it looks for me as you were writing a validator for user input. so (unfortunately I have to guess) in this respect you want only this number and nothing before or after.

Regex regex = new Regex(@"^\d{3}-\d{4}$");

This would mean you need to ensure that the first 3 digits are really in the beginning of the string using ^ otherwise IsMatch would return true because it finds the pattern in "something000-0000"

and that after the last 4 digits the string is at its end using $ otherwise IsMatch would return true because it finds the pattern in "000-0000something"