using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

public class Test
{
	public static void Main()
	{
		string notEmpty = "abc|CaptureMeButICanBeEmpty|def";
		string isEmpty = "abc||def";
		string regEx = @"^\w+\|([^|]+)?\|\w+$";
		var match = Regex.Match(notEmpty, regEx);
		var match2 = Regex.Match(isEmpty, regEx);
		
		var first = match.Groups[1].Success ? match.Groups[1].Value : "No ouptut";
		Console.WriteLine(first); // CaptureMeButICanBeEmpty
		var second = match2.Groups[1].Success ? match2.Groups[1].Value : "No ouptut";
		Console.WriteLine(second.ToString()); // No Output
	}
}