Text-Analyzer/Metoder/Form1.cs

using System;
using System.Drawing;
using System.Net.Security;
using System.Reflection;
using System.Text;
using System.Windows.Forms;
using static System.Net.Mime.MediaTypeNames;

namespace Metoder
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        // button binds
        private void btn_find_Click(object sender, EventArgs e)
        {
            string pattern = txtbx_find.Text;
            Highlight(pattern);
        }

        private void btn_replace_Click(object sender, EventArgs e)
        {
            string pattern = txtbx_find.Text;
            string replacement = txtbx_replace.Text;

            ReplaceFound(pattern, replacement);
        }

        private void btn_clear_Click(object sender, EventArgs e)
        {
            lbl_found.Visible = false;
        }

        private void btn_sort_Click(object sender, EventArgs e)
        {
            SortWords();
        }


        // methods
        void UpdateFindResult(int foundCount)
        {
            lbl_found.Visible = true;
            string suffix;

            // correct grammar
            if (foundCount == 1)
                suffix = " item found";
            else
                suffix = " items found";

            lbl_found.Text = foundCount.ToString() + suffix;
        }

        Dictionary<int, int> GetMatchesIndices(string pattern, string text)
        {
            Dictionary<int, int> dict = new Dictionary<int, int>();

            if (pattern == "") return dict; // avoid errors, infinite loop

            int index = 0;

            // find and save start index and length of each occurance
            while ((index = text.IndexOf(pattern, index, StringComparison.OrdinalIgnoreCase)) != -1)
            {
                dict[index] = pattern.Length;
                index += pattern.Length;
            }

            return dict;
        }

        void Highlight(string pattern)
        {
            RichTextBox richTextBox = txtbx_text;
            string text = richTextBox.Text;

            // reset old highlight
            richTextBox.SelectAll();
            richTextBox.SelectionBackColor = richTextBox.BackColor;

            int found = 0;
            int caret = richTextBox.SelectionStart; // set cursor to start

            foreach (KeyValuePair<int, int> occurance in GetMatchesIndices(pattern, text))
            {
                richTextBox.Select(occurance.Key, occurance.Value); // select pattern occurance
                richTextBox.SelectionBackColor = Color.LightBlue; // highlight
                found++;
            }

            // reset cursor
            richTextBox.Select(caret, 0);

            // update find label
            UpdateFindResult(found);
        }

        void ReplaceFound(string pattern, string replacement)
        {
            string text = txtbx_text.Text;

            Dictionary<int, int> matches = GetMatchesIndices(pattern, text);

            if (matches.Count == 0) return;

            string finalString = "";  // or string.Empty
            int currentIndex = 0;

            foreach (KeyValuePair<int, int> occurrence in matches)
            {
                // add text before occurrence
                if (occurrence.Key > currentIndex)
                {
                    finalString += text.Substring(currentIndex, occurrence.Key - currentIndex);
                }

                // add replacement to result
                finalString += replacement;

                // move past occurrence
                currentIndex = occurrence.Key + occurrence.Value;
            }

            // add remaining text
            if (currentIndex < text.Length)
            {
                finalString += text.Substring(currentIndex);
            }

            txtbx_text.Text = finalString;
        }

        void SortWords()
        {
            List<string> words = GetSortedWords(GetWords());

            string finalString = "";

            // add each sorted word separated by spaces
            foreach (string word in words)
            {
                finalString += word;
                finalString += " ";
            }

            txtbx_text.Text = finalString;
        }

        List<string> GetSortedWords(List<string> words)
        {
            words.Sort();

            return words;
        }

        List<string> GetWords() // get list of words separated by spaces
        {
            string text = txtbx_text.Text;
            string[] words = text.Split((char[])null, StringSplitOptions.RemoveEmptyEntries); // split by spaces

            return words.ToList();
        }
    }
}