Question

For a Username field there are certain varaitions that cannot be chosen as an appropiate username nor can certain characters be used.

For example: TIM1….TIM9 cannot be used BIN1….BIN9 cannot be used, nor can the characters <>:\/|?* appear anywhere in the field.

The code I have so far is thus:

    private bool ValidateId(string regexValue)
    {
        Regex regex = new Regex("TIM[1-9]|BIN[1-9]|[<>:\"/|?*]");
        return !regex.IsMatch(regexValue);
    }

What I’m struggling to allow for however is the backslash character. Trying to escape it as I have done with the quotation character doesn’t appear to work.

Thanks in advance.

Answer 1

You need to do a double escape. Try this:

Regex regex = new Regex("TIM[1-9]|BIN[1-9]|[<>:\\\\\"/|?*]");

Explanation:

You need to escape the backslash in C# strings to get a backslash in the string. Additionally, the string needs to have two backslashes, because Regex also requires the backslashes to be escaped.

BTW, using verbatim strings makes it a bit more readable:

Regex regex = new Regex(@"TIM[1-9]|BIN[1-9]|[<>:\\""/|?*]");

Both codes will result in a Regex with this expression:

TIM[1-9]|BIN[1-9]|[<>:\\"/|?*]