using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		var myResponse = @"<td colspan=""2"" class=""invalid"">
  28 Errors, 3 warning(s)


</td>";
        var TdTag = Regex.Matches(myResponse, @"(?s)<td[^<]*>\s*(\d+)[^<]*</td>");
        var result = TdTag[0].Groups[1].Value;
        Console.WriteLine(result);
	}
}