How do I extract text that lies between parentheses (round brackets)?

If you wish to stay away from regular expressions, the simplest way I can think of is:

string input = "User name (sales)";
string output = input.Split('(', ')')[1];

A very simple way to do it is by using regular expressions:

Regex.Match("User name (sales)", @"\(([^)]*)\)").Groups[1].Value

As a response to the (very funny) comment, here's the same Regex with some explanation:

\(             # Escaped parenthesis, means "starts with a '(' character"
    (          # Parentheses in a regex mean "put (capture) the stuff 
               #     in between into the Groups array" 
       [^)]    # Any character that is not a ')' character
       *       # Zero or more occurrences of the aforementioned "non ')' char"
    )          # Close the capturing group
\)             # "Ends with a ')' character"