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

public class Test
{
	public static void Main()
	{
		 var text = "int rn = 0; //comment1.0\r\n" +
                   "int r = 0; //comment2.\r" + 
                   "int n = 0; //comment3.\n" + 
                   "end";
        Console.WriteLine(RemoveLineEndComment(text));
	}

    public static string RemoveLineEndComment(string text)
	{
		var RegexRemoveLineEndComment =  new Regex(@"\s*//[^\r\n]*", RegexOptions.Multiline);
	    return RegexRemoveLineEndComment.Replace(text, string.Empty);
	}
}