c# - How to find longest sentence in text?

Question

Let's say I have text file similar to this:

C#[note 2] (pronounced as see sharp) is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. It was developed by Microsoft within its .NET initiative and later approved as a standard by Ecma (ECMA-334) and ISO (ISO/IEC 23270:2006). C# is one of the programming languages designed for the Common Language Infrastructure. C# is intended to be a simple, modern, general-purpose, object-oriented programming language.[7] Its development team is led by Anders Hejlsberg. The most recent version is C# 6.0, which was released on July 20, 2015.[8]

How can I find longest sentence in this text? Should I read it using string[] lines = File.ReadAllLines(file);?

Edit: You say is impossible. But this was a task i was given by a teacher..

Okay, how to do this with this text file?:

Text messaging, or texting, is the act of composing and sending brief, electronic messages between two or more mobile phones, or fixed or portable devices over a phone network. The term originally referred to messages sent using the Short Message Service (SMS). It has grown to include messages containing image, video, and sound content (known as MMS messages). The sender of a text message is known as a texter, while the service itself has different colloquialisms depending on the region. It may simply be referred to as a text in North America, the United Kingdom, Australia, New Zealand and the Philippines, an SMS in most of mainland Europe, and an MMS or SMS in the Middle East, Africa, and Asia.

Answer 1

If you really want to split English text by sentences (and not just for a homework exercise), I would recommend the use of one of the open source natural language processing tools, for example SharpNLP which is a C# port of the Java OpenNLP tools. I have downloaded the source code for this from GitHub and created the following example in its Test project. This program outputs 6 sentences and the longest sentence is actually the first sentence.

using OpenNLP.Tools.SentenceDetect;

namespace Test
{
    internal class Program
    {
        private static readonly string currentDirectory = Environment.CurrentDirectory + "/../../";

        private static void Main(string[] args)
        {

            var inputText =
                "C#[note 2] (pronounced as see sharp) is a multi-paradigm programming language encompassing strong typing, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. It was developed by Microsoft within its .NET initiative and later approved as a standard by Ecma (ECMA-334) and ISO (ISO/IEC 23270:2006). C# is one of the programming languages designed for the Common Language Infrastructure. C# is intended to be a simple, modern, general-purpose, object-oriented programming language.[7] Its development team is led by Anders Hejlsberg. The most recent version is C# 6.0, which was released on July 20, 2015.[8]";
            var sentenceDetector =
                new EnglishMaximumEntropySentenceDetector(currentDirectory + "../Resources/Models/EnglishSD.nbin");
            string[] sentences = sentenceDetector.SentenceDetect(inputText);


            string longest = sentences.OrderByDescending(s => s.Length).First();
        }
    }
}