如何将regex match.Value转换为整数？

Question

List<int> ids = ExtractIds("United Kingdom (656) - Aberdeen (7707)");

The above list should be populated by the method below, which strips the values from within parenthesis.

If I use match.Value as a string and assign it to List< string > it seems to work ok. But when I try to convert it to an integer I get the error: "Input string was not in a correct format."

What am I doing wrong?

public List<int> ExtractIds(string str)
{
    MatchCollection matchCollection = Regex.Matches(str, @"\((.*?)\)");
    List<int> ExtractedIds = new List<int>();
    foreach (Match match in matchCollection)
    {
        int theid = int.Parse(match.Value);
        ExtractedIds.Add(theid);
    }

    return ExtractedIds;
}

Answer 1

Use match.Groups[1].Value instead of match.Value to just get the string found inside the brackets - ie not including the brackets themselves.

Use \\d*? instead of .?* to ensure you're only matching digits, not anything in brackets!

Then you don't even need the ? any more because \\d doesn't match a closing bracket.

Instead of switching to look in Groups[1] , you can use lookarounds in a regular expression such as

(?<=\()\d(?=\))

to make sure Match only contains the digits themselves.

Answer 2

If you debug your code, you are getting match.Value includes the brackets around the number, this will obviously throw exception.

rewrite you pattern as @"(\\d)+" this will group your number but ignore the brackets.

public List<int> ExtractIds(string str)
{
     MatchCollection matchCollection = Regex.Matches(str, @"(\d)+");
     List<int> ExtractedIds = new List<int>();
     foreach (Match match in matchCollection)
     {
         int theid = int.Parse(match.Value);
         ExtractedIds.Add(theid);
      }
      return ExtractedIds;
 }

Hope this helps.