Fixing Broken Lines, C#

Language: Layout:

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

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

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            bool joinLines=false;
            string lastLine=default(string),line;
            
            while((line=Console.ReadLine())!=default(string)){
                
                if(joinLines)lastLine+=line;
                
                bool brokenLine=Regex.Replace(line,"[^\"]",string.Empty).Length%2==1;
                string printLine=default(string);
                
                if(brokenLine){
                    if(joinLines)printLine=lastLine;else lastLine=line;
                    joinLines=!joinLines;
                }else{
                    if(joinLines==false)printLine=line;
                }
                
                if(printLine!=default(string))Console.WriteLine(printLine);
                
            }
        }
    }
}

Show compiler warnings [ - ] Show input
Compilation time: 0,14 sec, absolute running time: 0,19 sec, cpu time: 0,19 sec, average memory usage: 17 Mb, average nr of threads: 4