Simple regex pattern

Question

i'm using C# and i'm trying to allow only alphabetical letters and spaces. my expression at the moment is:

string regex = "^[A-Za-z\s]{1,40}$";

my IDE says that \s is an "Unrecognized escape sequence"

what am i missing?

Answer 1

You need to put an @ in front of your string to turn it into a verbatim string literal:

string regex = @"^[A-Za-z\s]{1,40}$";

Right now, the \ in your regex is being interpreted as trying to escape the following s, which the compiler doesn't understand.

Alternatively, you can just escape the backslash with another one:

string regex = "^[A-Za-z\\s]{1,40}$";

but in general, prefer the first approach to the second.

Answer 2

"\" is a c# escape character as well as a regex escape character. Try:

string regex = @"^[A-Za-z\s]{1,40}$";

Answer 3

Also for your reference:

link text

Answer 4

An additional note, your regex doesn't do what you describe. You say a max of 1 space in between words. In order to do that, you need to move the "\s" out of the character list. The pattern you're currently using allows "any alphanumeric or space from 1 to 40 times" which allows for multiple successive spaces. You'll need something more like the following:

string regex = @"^(?:[A-Za-z]+\s?)+$";

This means "any alphanumeric 1 or more times followed by an optional space, this whole thing one or more times". I don't know how to limit the whole string to 40 characters when you don't know the size of the first expression in advance. Maybe this can be achieved with a "look behind" expression, but I'm not sure. You might have to do it in two steps.