using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

public static class StringExtensions

    {

​

        public static string TruncateAtFirstSentence(this string value, int maxLength)

        {

            char[] punc = new char[3];

            punc[0] = '.';

            punc[1] = '!';

            punc[2] = '?';

​

            // not the best programming, basically falls though when requirements

            // arent met. 

            foreach (char c in value) {

​

                if (c == punc[2]) {

                    var str = value.Substring(0, value.IndexOf("?") + 1);

                    if (str.Length <= 30)

                        continue;

                    else 

                    {

                        if (str.Length > maxLength)

                        {

                            continue;

                        }

                        else

                        {

                            return str;

                        }

                    }

                }

                else if (c == punc[1]) {

​

                    var str = value.Substring(0, value.IndexOf("!") + 1);

​

                    if (str.Length <= 30)

                        continue;

                    else 

                    {

                        if (str.Length > maxLength)

                        {

                            continue;

                        }

                        else

                        {

                            return str;

                        }

                    }

                }

                else if (c == punc[0]) {

​

                    var str = value.Substring(0, value.IndexOf(".") + 1);

                    if (str.Length <= 30)

                        continue;

                    else 

                    {

                        if (str.Length > maxLength)

                        {

                            continue;

                        }

                        else

                        {

                            return str;

                        }

                    }

                }

            }

​

            var output = value.Length <= maxLength ? value : value.Substring(0, maxLength);

            output = output.Substring(0, output.LastIndexOf(' '));

​

            return output + "...";

        }

    }

​

public class Program

{

    public static void Main()

    {

        string sentence = "This is a simple! question that ends with! a question mark? This is nearly the same. sentence that also ends with a period.";

        string longSentence = "This is a simple question that does not end with a question mark This is sort of the same sentence that ends with a period.";

        var output = StringExtensions.TruncateAtFirstSentence(sentence, 100);

        var output2 = StringExtensions.TruncateAtFirstSentence(longSentence, 100);

        Console.WriteLine("output 1: \n{0}\n", output);

        Console.WriteLine("output 2: \n{0}\n", output2);

    }

}