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());
		}
	}
}

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