using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Enter sentence for conversion");

        string input =Console.ReadLine();

        string output = Paragraph.ToSentenceCase(input);    

        Console.WriteLine(output);

    }

}

public abstract class Paragraph

{

/// <summary>

/// Convert a string in arbitrary case to English sentence capitalisation.

/// </summary>

/// <param name="text">The text to convert</param>

/// <returns>The paragraph of text</returns>

public static string ToSentenceCase(string text)

{

string temporary = text;

string result = "";

while (temporary.Length>0)

{

string[] splitTemporary = splitAtFirstSentence(temporary);

temporary = splitTemporary[1];

if (splitTemporary[0].Length>0)

{

result += capitaliseSentence(splitTemporary[0]);

}

else

{

result += capitaliseSentence(splitTemporary[1]);

temporary = "";

}

}

return result;

}

​

private static string capitaliseSentence(string sentence)

{

string result = "";

while (sentence[0]==' ')

{

sentence = sentence.Remove(0,1);

result+=" ";

}

if (sentence.Length>0)

{

result += sentence.TrimStart().Substring(0, 1).ToUpper();

result += sentence.TrimStart().Substring(1, sentence.TrimStart().Length-1);

}

return result;

}

​

private static string[] splitAtFirstSentence(string text)

{

//these are the characters to start a new sentence after

int lastChar = text.IndexOfAny(new char[] {'.', ':', '\n', '\r', '!', '?'})+1;

if (lastChar==1)

{

lastChar = 0;

}

return new string[] { text.Substring(0, lastChar), text.Substring(lastChar, text.Length-lastChar) };

}

}