Convert result of matches from regex into list of string

Question

How can I convert the list of match result from regex into List<string>? I have this function but it always generate an exception,

Unable to cast object of type 'System.Text.RegularExpressions.Match' to type 'System.Text.RegularExpressions.CaptureCollection'.

public static List<string> ExtractMatch(string content, string pattern) {     List<string> _returnValue = new List<string>();     Match _matchList = Regex.Match(content, pattern);     while (_matchList.Success)     {         foreach (Group _group in _matchList.Groups)         {             foreach (CaptureCollection _captures in _group.Captures) // error             {                 foreach (Capture _cap in _captures)                 {                     _returnValue.Add(_cap.ToString());                 }             }         }     }     return _returnValue; } 

If I have this string,

I have a dog and a cat. 

regex

dog|cat 

I want that the function will return of result into List<string>

dog cat 

Answer 1

With the Regex you have, you need to use Regex.Matches to get the final list of strings like you want:

MatchCollection matchList = Regex.Matches(Content, Pattern); var list = matchList.Cast<Match>().Select(match => match.Value).ToList(); 

Answer 2

To get just a list of Regex matches, you may:

var lookfor = @"something (with) multiple (pattern) (groups)"; var found = Regex.Matches(source, lookfor, regexoptions); var captured = found                 // linq-ify into list                 .Cast<Match>()                 // flatten to single list                 .SelectMany(o =>                     // linq-ify                     o.Groups.Cast<Capture>()                         // don't need the pattern                         .Skip(1)                         // select what you wanted                         .Select(c => c.Value)); 

This will "flatten" all the captured values down to a single list. To maintain capture groups, use Select rather than SelectMany to get a list of lists.