Regex to match alphanumeric and spaces

What am I doing wrong here?

string q = "john s!";
string clean = Regex.Replace(q, @"([^a-zA-Z0-9]|^\s)", string.Empty);
// clean == "johns". I want "john s";

Solution 1:

just a FYI

string clean = Regex.Replace(q, @"[^a-zA-Z0-9\s]", string.Empty);

would actually be better like

string clean = Regex.Replace(q, @"[^\w\s]", string.Empty);

Solution 2:

This:

string clean = Regex.Replace(dirty, "[^a-zA-Z0-9\x20]", String.Empty);

\x20 is ascii hex for 'space' character

you can add more individual characters that you want to be allowed. If you want for example "?" to be ok in the return string add \x3f.