using System;

using System.Text; 

using System.IO;

using System.Diagnostics;

using System.Text.RegularExpressions;

    public static class Program

    {

​

        public static string RemoveAllWhitespace(this string str)

        {

            var len = str.Length;

            var src = str.ToCharArray();

            var dstIdx = 0;

            for (var i = 0; i < len; i++)

            {

                char ch = src[i];

                if (!char.IsWhiteSpace(ch) && ch != '\0')

                    //ch!='\0')

                    src[dstIdx++] = ch;

            }

            return new string(src, 0, dstIdx);

        }

​

​

        public static string TrimStartUnicode(this string str)

        {

            var len = str.Length;

            var src = str.ToCharArray();

            var dstIdx = 0;

            for (var i = 0; i < len; i++)

            {

                char ch = src[i];

                if (!char.IsWhiteSpace(ch) && !char.IsControl(ch) ) 

                {

                    src[dstIdx++] = ch;

                    break;

                }

            }

            return new string(src, 0, dstIdx);

        }

​

        private static readonly char[] TrimNewLineChars = Environment.NewLine.ToCharArray();

        public static string RemoveEmptyLines(this string str)

        {

            if (str == null)

            {

                return null;

            }

            var lines = str.Split(TrimNewLineChars, StringSplitOptions.RemoveEmptyEntries);

​

            var sb = new StringBuilder(str.Length);

            foreach (var line in lines)

            {

                if (!String.IsNullOrWhiteSpace(line))

                    sb.AppendLine(line);

            }

​

            return sb.ToString();

        }

​

        //Tue 12-May-20 2:08am  - 

        public static String RemoveAllBlankLinesIssue(this string value)

        {

​

            StringBuilder output = new StringBuilder(value.Length);

            using (StringReader sr = new StringReader(value))

            {

                string line;

                while ((line = sr.ReadLine()) != null)

                {

                    //\0 has no special meaning in c# it's just a null character contained in a string.

                    if (line == '\0'.ToString()) //is line length of 1

                    {

​

                        Console.WriteLine("is string '\\0' empty or null = " + string.IsNullOrEmpty('\0'.ToString()));

                        Console.WriteLine("is string '\\0' whitespace or null = " + String.IsNullOrWhiteSpace('\0'.ToString()));

                        Console.WriteLine("is char '\\0' char.IsWhiteSpace = " + char.IsWhiteSpace('\0')); 

                        Console.WriteLine("is char '\\0' char.IsControl = " + char.IsControl('\0')); 

                    }

                    if (line.Contains('\u0080'.ToString()))

                    {

                        Console.WriteLine("is string '\\0080' empty or null = " + string.IsNullOrEmpty('\u0080'.ToString()));

                        Console.WriteLine("is string '\\0080' whitespace or null = " + String.IsNullOrWhiteSpace('\u0080'.ToString()));

​

                    }

​

                    if (!String.IsNullOrWhiteSpace(line) && !string.IsNullOrEmpty(line))

                        output.AppendLine(line);

                }

​

            }

            return output.ToString();

        }

​

        //Tue 12-May-20 2:08am  - 

        public static String RemoveAllBlankLinesFinal(this string value)

        {

            StringBuilder output = new StringBuilder(value.Length);

            using (StringReader sr = new StringReader(value))

            {

                string line;

                string temp; 

                while ((line = sr.ReadLine()) != null)

                {

                    temp = line.TrimStartUnicode();  

                    if (!string.IsNullOrWhiteSpace(temp) && !string.IsNullOrEmpty(temp))

                        output.AppendLine(line);

                }

​

            }

            return output.ToString();

        }

​

​

​

        public static String RemoveAllBlankLinesRegex(this string s)

        {

            return Regex.Replace(s, @"^\s+$[\r\n]*", string.Empty, RegexOptions.Multiline);

            //return Regex.Replace(s, @"^(?:[\t ]*(?:\r?\n|\r))+", string.Empty, RegexOptions.Multiline); 

            //return Regex.Replace(s, @"(?<=(?:\r?\n){2}|\A)(?:\r?\n)+", string.Empty, RegexOptions.Multiline); 

            //return Regex.Replace(s, @"(?<=(?:\r?\n){2}$\w)(?:\r?\n)+", string.Empty, RegexOptions.Multiline); 

            //return Regex.Replace(s, @"^\s*(\r\n|\V)", string.Empty, RegexOptions.Multiline); //does not work

​

        }

​

        public static void Main()

        {

            string output = string.Empty;

​

            Stopwatch sw = new Stopwatch();

​

            string emptytest = "Tell me and I forget.\n \n     \nTeach me and I remember.     \r\n \r\n\r\nInvolve me and I learn.  \r     \r\r\0\r\r   Pad Unicode \\u0080 next line\n\n\u0080\r\rby Benjamin Franklin.\r\n";

​

            sw.Start();

            output = emptytest.RemoveEmptyLines();

            sw.Stop();

            Console.WriteLine(output + " in " + sw.ElapsedTicks + " ticks");

​

            Console.WriteLine();

            Console.WriteLine("-------- StringReader Issue ----------------");

            sw.Reset();

            sw.Start();

            output = emptytest.RemoveAllBlankLinesIssue();

            sw.Stop();

            Console.WriteLine(output + " in " + sw.ElapsedTicks + " ticks");

​

​

            Console.WriteLine();

            Console.WriteLine("-------- StringReader Final ----------------");

            sw.Reset();

            sw.Start();

            output = emptytest.RemoveAllBlankLinesFinal();

            sw.Stop();

            Console.WriteLine(output + " in " + sw.ElapsedTicks + " ticks");

​

​

​

​

​

​

​

​

            Console.WriteLine();

            Console.WriteLine("-------- Regex ----------------");

​

            sw.Reset();

            sw.Start();

            output = emptytest.RemoveAllBlankLinesRegex();

            sw.Stop();

​

            Console.WriteLine(output + "\n in " + sw.ElapsedTicks + " ticks");

​

​

        }

    }