Regular Expression Groups in C#

by
  • match.Groups[0] is always the same as match.Value, which is the entire match.
  • match.Groups[1] is the first capturing group in your regular expression.

Consider this example:

var pattern = @"\[(.*?)\](.*)";
var match = Regex.Match("ignored [john] John Johnson", pattern);

In this case,

  • match.Value is "[john] John Johnson"
  • match.Groups[0] is always the same as match.Value, "[john] John Johnson".
  • match.Groups[1] is the group of captures from the (.*?).
  • match.Groups[2] is the group of captures from the (.*).
  • match.Groups[1].Captures is yet another dimension.

Consider another example:

var pattern = @"(\[.*?\])+";
var match = Regex.Match("[john][johnny]", pattern);

Note that we are looking for one or more bracketed names in a row. You need to be able to get each name separately. Enter Captures!

  • match.Groups[0] is always the same as match.Value, "[john][johnny]".
  • match.Groups[1] is the group of captures from the (\[.*?\])+. The same as match.Value in this case.
  • match.Groups[1].Captures[0] is the same as match.Groups[1].Value
  • match.Groups[1].Captures[1] is [john]
  • match.Groups[1].Captures[2] is [johnny]

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