C# Regex: Checking for “a-z” and “A-Z”

Question

I want to check if a string inputted in a character between a-z or A-Z. Somehow my regular expression doesn\'t seem to pick it up. It always returns true. I am not sure why,

Answer 1

The right way would be like so:

private static bool isValid(String str)
{
    return Regex.IsMatch(str, @"^[a-zA-Z]+$");
}

This code has the following benefits:

• Using the static method instead of creating a new instance every time: The static method caches the regular expression
• Fixed the regex. It now matches any string that consists of one or more of the characters a-z or A-Z. No other characters are allowed.
• Much shorter and readable.

Answer 2

Use

Regex.IsMatch(@"^[a-zA-Z]+$");

Answer 3

Regex reg = new Regex("^[a-zA-Z]+$");

• ^ start of the string
• [] character set
• \+ one time or the more
• $ end of the string

^ and $ needed because you want validate all string, not part of the string