Why does the regex work not as expected?

Question

There is a string which can have one or several string ranges. These are correct strings:

\"\"
\"asd-asd\"
\"asd-asd;asd-asd\"
\"asd-asd;asd-asd;\"
\"asd-asd;asd         


        

Answer 1

There's a slight add to the Answer of @Tim. This regex is not matching the "asd-asd;asd-asd;" if you're using .Net regex library. But if you add a ';' as option before string ends then it'll cover all the cases.

^([^;-]+-[^;-]+(;[^;-]+-[^;-]+)*);?$

Now this will match all the valid strings provided except the Invalid - "asd0-asd1-asd2"

Answer 2

It matches because of ;? which makes the ; optional. You are trying to test something with context, regex is not the easiest tool to do this.

Answer 3

You need to make your regex a little more complicated:

^([^;-]+-[^;-]+(;[^;-]+-[^;-]+)*)?$

Explanation:

^               # Start of the string
(               # Start of first group:
 [^;-]+-[^;-]+  # Match one "asd-asd"
 (              # Start of second group
  ;             # Match ;
  [^;-]+-[^;-]+ # Match another "asd-asd"
 )*             # Repeat the second group any number of times (including zero)
)?              # Make the entire first group optional     
$               # End of string

Answer 4

To avoid making the semicolon optional, instead you could use (;|$).
This will force the match of a semicolon unless you are at the end of the string.

^(([^;-]+-[^;-]+)(;|$))*$