Phone and ZIP format checker examples from C# .NET

It’s a common task to check the validity of an input in any application. Some inputs must follow a specific format, like phone numbers and ZIP codes. Here come two regular expression examples that will help you with that:

private static bool IsValidPhone(string candidate)
{
	return Regex.IsMatch(candidate, @"^\(?\d{3}\)?[\s\-]?\d{3}\-?\d{4}$");
}

The above regular expression will return true for the following formats:

• (xxx)xxx-xxxx: (123)456-7890
• (xxx) xxx-xxxx: (123) 456-7890
• xxx-xxx-xxxx: 123-456-7890
• xxxxxxxxxx: 1234567890

Let’s now see a possible solution for a US ZIP code:

private static bool IsValidZip(string candidate)
{
	return Regex.IsMatch(candidate, @"^\d{5}(\-\d{4})?$");
}

This function returns true for the following formats:

• xxxxx-xxxx: 01234-5678
• xxxxx: 01234

View all posts related to string and text operations here.