using System.Text.RegularExpressions;
public static void Main()
Regex regex = new Regex(@"<size(\s+)?=(\s+)?(.*)>", RegexOptions.Compiled);
var match = regex.Match(@"<size=50>");
Console.WriteLine("Not matched!");
foreach (Group group in match.Groups)
Console.WriteLine("Group " + groupIndex + ". : " + group.Name);
foreach (Capture capture in group.Captures)
Console.WriteLine("Capture " + captureIndex + ". : " + capture.Value);