using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.IO;
using System.Text.RegularExpressions;
using System.Text;

namespace SpellCheck
{
    public class SpellChecker
    {
        // Class declarations
        private StringCollection scDictionary = new StringCollection();
        private StringCollection scNotFound = new StringCollection();
        private string strMarkedText;
        private string strStatus;

        // Properties
        public StringCollection Dictionary { get { return scDictionary; } }
        public StringCollection NotFound { get { return scNotFound; } }
        public string MarkedText { get { return strMarkedText; } }
        public string Status { get { return strStatus; } }

        // Constructor
        public SpellChecker(string Text, string DictionaryFile, string Prefix, string Suffix)
        {
            strStatus = "";
            // Load Dictionary file
            ReadDictionaryFile(DictionaryFile);
            if (strStatus == "")
            {
                // Split the provided text into a string array of words
                string[] strWords = SplitWords(Text);
                // Build collection of "not found" words
                CheckWords(strWords);
                // Create a new string with potentially incorrect words marked
                strMarkedText = MarkText(Text, Prefix, Suffix);
            }
        }

        // Load dictionary
        private void ReadDictionaryFile(string strFilename)
        {
            string strLine;
            StreamReader srDictionary = null;
            System.Diagnostics.Debug.WriteLine("Reading dictionary");
            try
            {
                if (File.Exists(strFilename))
                {
                    // Create new StreamReader for dictionary file
                    srDictionary = new StreamReader(strFilename);
                }
                else
                {
                    System.Diagnostics.Debug.WriteLine("Not Found:" + strFilename);
                    return;
                }


                // Get initial word
                strLine = srDictionary.ReadLine();

                // Read while not EOF
                while (strLine != null)
                {
                    // Add line to StringCollection
                    scDictionary.Add(strLine.ToLower());
                    // Get next word
                    strLine = srDictionary.ReadLine();
                }
                System.Diagnostics.Debug.WriteLine("Done reading dictionary");
            }
            catch (Exception ex)
            {
                strStatus = ex.Message;
                System.Diagnostics.Debug.WriteLine(strStatus);
            }
            finally
            {
                if(srDictionary != null)
                    srDictionary.Close();
            }
        }

        // Split text into individual words
        private string[] SplitWords(string strText)
        {
            System.Diagnostics.Debug.WriteLine("Splitting words");
            // Define string delimiters
            char[] cDelimiters = { ' ', ',', '.', '?',
                ':', '/', '=', '~', '+', '-', '\"',
                '\t', '\r', '\n', '“', '”', '`', '’',
                '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                '#', '$', '&', '%', '@', '!', '(', ')' };

            // Split the provided text into individual words
            string[] straWords = strText.Split(cDelimiters);
            System.Diagnostics.Debug.WriteLine("Done splitting words");
            return straWords;
        }

        // Determine whether each word exists in the dictionary
        private void CheckWords(string[] strWords)
        {
            System.Diagnostics.Debug.WriteLine("Building word list");
            // Build a list of words that weren't found in the dictionary
            foreach (string Word in strWords)
            {
                // If word lengh = 0, it may be a control character, so skip it
                // Otherwise, go ahead and try to add it to the missing word list
                if (!scDictionary.Contains(Word.ToLower()) && Word.Length > 0)
                {
                    // If the missing word list doesn't already have this word, add it
                    if (!scNotFound.Contains(Word.ToLower()))
                        scNotFound.Add(Word);
                }
            }
            System.Diagnostics.Debug.WriteLine("Done building word list");
        }

        // Mark original text with provided prefix and suffix strings
        private string MarkText(string Text, string strPrefix, string strSuffix)
        {
            System.Diagnostics.Debug.WriteLine("Marking text");
            string strText = Text;
            string strReplacement = "";
            // Mark not-found words in original text
            foreach (string Word in scNotFound)
            {
                strReplacement = (strPrefix + Word + strSuffix);
                strText = Regex.Replace(strText, Word, strReplacement);
            }
            System.Diagnostics.Debug.WriteLine("Done marking text");
            return strText;
        }
    }
}

SpellCheck.SpellChecker spellcheck = new SpellCheck.SpellChecker(txtBox.Text, "words.txt", "", "");

            System.IO.StreamReader reader = new System.IO.StreamReader("words.txt");
            SpellCheck.SpellChecker spellcheck = new SpellCheck.SpellChecker(reader.ReadLine(), "words.txt", "", "");
            reader.Close();