using System;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string sourceText = "This will contain a bunch of text. Might also contain EMP 1234 and there could be a bunch of text after this pattern. There could again be EMP 4567 or http://emps/2345 We'll be extracting all such patterns. 3 in this case.";
		const string regexPattern = @"\b(?:EMP(?:id|[s:#])?\s+(?<EMPid>\d{1,11})|(?<EMPurl>https?://emps/\d+))(?!\S)";
		var search = new Regex(regexPattern , RegexOptions.IgnoreCase);
		MatchCollection matches = search.Matches(sourceText);
		
		foreach (Match match in matches)
		{
		    Console.WriteLine(match.Value.ToString());
		}
	}
}