How to create a regex for following condition?

Question

Hi,

I was creating a regex for following condition

a string can contain any alphabet, digit and ' and ? the string should start with either alphabet or digit

for ex:

adsfj
asfj's
jfkd'sdf?
df
ds?
afjdk?

are all valid

I use C# 2.0

I tried something like this

  ^[a-zA-Z0-9]+[']\*[a-zA-Z0-9]\*[?]\*[a-zA-Z0-9]\*$

which did not solve the problem.... any idea..?

Answer 1

How about:

Regex rx = new Regex(@"^[a-z\d][a-z\d'?]*$", RegexOptions.IgnoreCase);

This would match just as you say: Starts with: any letter from the alphabet or a digit. Until the end it can contain: any letter from the alphabet, a digit, ' or ? characters.

Answer 2

^[a-zA-Z0-9][a-zA-Z0-9?']*$

This would even allow strings of length one. To specify a minimum and maximum lengths, change the regex to:

^[a-zA-Z0-9][a-zA-Z0-9?']{minlen-1,maxlen - 1}$

For example, the following allows strings of length five to 10.

^[a-zA-Z0-9][a-zA-Z0-9?']{4,9}$

Answer 3

It's simpler than you made it: ^[a-zA-Z\d][a-zA-Z\d'?]*$

^            # Start of string anchor.
[a-zA-Z\d]   # First character is a letter or a digit.
[a-zA-Z\d'?] # Subsequent characters are letters, digits, apostrophes or question marks...
*            # ...repeated any number of times.
$            # Until the end of the string.

If you allow underscores with your other characters, it can be simplified to: ^\w[\w'?]*$