Михаил

List<string> words = new List<string> { "hello", "World" };
		string pattern = "("+ string.Join("|", words) + "),";
		Console.WriteLine(pattern);
		Regex r = new Regex(pattern, RegexOptions.IgnoreCase);
		
		string text = "Hello, World, hello world heelo";
		var matches = r.Matches(text);
		foreach(var match in matches){
			Console.WriteLine(match);
		}