How to Find or Validate an Email Address

Validating regular expression

We want to use parentheses as literals, and not as special characters. We can validate a field as each character is entered. Because no backtracking is needed to find matches, doing this does not change what is matched by these regexes.

TryParse for the completion validator. This control allows you to restrict text entry to any format that can be described with a regular expression, which essentially means any format at all. Adding a check to make sure that the match found is equal to the entire string will make this routine work correctly.

We want to use parenthesesWe can validate a

We don't need to repeat the initial character check when checking the length of the local part. To do that, we simply escape them by adding a backslash in front of them.

Validate Textbox with Regular Expressions

So with a single-character local part, a two-letter top-level domain and single-character sub-domains, is the maximum number of sub-domains. Empty strings are now disallowed. If you want to know all the trade-offs and get plenty of alternatives to choose from, read on. We can validate each field as it is completed.

Now type something, anything, in the Test box. Alternates are specified by using the pipes character within a group.

Because no backtracking is needed to

All of these regexes allow the characters. And you have to turn on the case insensitive matching option. In the Test box, try entering a space after one of the commas. See if you can modify the last regex to allow unlimited spaces.