What is wrong with this Regular Expression?

Question

I am beginner and have some problems with regexp.

Input text is : something idUser=123654; nick="Tom" something

I need extract value of idUser -> 123456

I try this:

//idUser is already 8 digits number
        MatchCollection matchsID = Regex.Matches(pk.html, @"\bidUser=(\w{8})\b");
        Text = matchsID[1].Value;

but on output i get idUser=123654, I need only number

The second problem is with nick="Tom", how can I get only text Tom from this expresion.

Answer 1

Use look-around

(?<=idUser=)\d{1,8}(?=(;|$))

To fix length of digits to 6, use (?<=idUser=)\d{6}(?=($|;))

Answer 2

Here's a pattern that should work:

\bidUser=(\d{3,8})\b|\bnick="(\w+)"

Given the input string:

something idUser=123654; nick="Tom" something

This yields 2 matches (as seen on rubular.com):

• First match is User=123654, group 1 captures 123654
• Second match is nick="Tom", group 2 captures Tom

Some variations:

• In .NET regex, you can also use named groups for better readability.
• If nick always appears after idUser, you can match the two at once instead of using alternation as above.
• I've used {3,8} repetition to show how to match at least 3 and at most 8 digits.

API links

• Match.Groups property
  • This is how you get what individual groups captured in a match

Answer 3

you don't show your output code, where you get the group from your match collection.

Hint: you will need group 1 and not group 0 if you want to have only what is in the parentheses.

Answer 4

.*?idUser=([0-9]+).*?

That regex should work for you :o)