rtf find form

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace Rich_Text_Editor
{
    public partial class frmFindReplace : Form
    {
        public frmFindReplace()
        {
            InitializeComponent();
        }
        RichTextBox frm1RTB;// declares the frm1RTB variable
        int textFound;// declares the textFound variable
        public void btnFind_Click(object sender, EventArgs e)//finds text specified in the txtSearch text box
        {
            frm1RTB = ((frmRichTextEditor)this.Owner).rtbContent;//; assigns the frm1 rtb variable the value of the rich text box in form 1
            textFound = frm1RTB.Text.IndexOf(txtSearch.Text);// sets the textFound variable to the index of text value of the txtSearch box found in the frm1RTB
            if (textFound != -1)// if textFound is not -1 (if there is text found)
            {
                int selectionLength = txtSearch.TextLength;// sets the selectionLength variable to the length of the control text that was searched
                frm1RTB.Select(textFound, selectionLength);// selects the text in the richtextbox at the index of the text found for the selection length
                frm1RTB.Focus();// focus on the form 1 rich text box
                btnFindNext.Enabled = true;// enable the find next button
                btnReplace.Enabled = true;// enable the replace button
                btnReplaceAll.Enabled = true;// enable the replace all button
            }
            else// else (if there is no text found)
            {
                MessageBox.Show("Text Was Not Found", "Error");// tells the user there was no text found in the rich text box
            }
        }
        public void btnFindNext_Click(object sender, EventArgs e)// this button finds the next value in the rtb, after the first value was found.
        {
            frm1RTB = ((frmRichTextEditor)this.Owner).rtbContent;// assigns the frm1 rtb variable the value of the rich text box in form 1
            textFound = frm1RTB.Text.IndexOf(txtSearch.Text, textFound+1);// sets the text found variable to the index of the last found text +1, so it finds the bext whole match
            if (textFound != -1)// if textFound is not -1 (if there is text found)
            {
                int selectionLength = txtSearch.TextLength;// sets the selectionLength variable to the length of the control text that was searched
                frm1RTB.Select(textFound, selectionLength);// selects the text in the richtextbox at the index of the text found for the selection length
                frm1RTB.Focus();// focus on the form 1 rich text box
            }
            else// else (if there is no text found)
            {
                btnReplace.Enabled = false;// disable the replace button
                btnReplaceAll.Enabled = false;// disable the replace all button
                MessageBox.Show("Text Was Not Found", "Error");// tells the user there was no text found in the rich text box
            }
        }
        public void btnReplace_Click(object sender, EventArgs e)// replaces the current selected item supplied by the find function
        {
            {
                frm1RTB = ((frmRichTextEditor)this.Owner).rtbContent;// assigns the frm1 rtb variable the value of the rich text box in form 1
                textFound = frm1RTB.Text.IndexOf(txtSearch.Text);// sets the text found variable to the index of the last found text +1, so it finds the bext whole match
                if (textFound != -1 && txtReplace.Text != "")// if there was text found and the txtReplace text box is not nothing
                {
                    int selectionLength = txtSearch.TextLength;// sets the selectionLength variable to the length of the control text that was searched
                    frm1RTB.Select(textFound, selectionLength);// selects the text in the richtextbox at the index of the text found for the selection length
                    frm1RTB.SelectedText = frm1RTB.SelectedText.Replace(frm1RTB.SelectedText, txtReplace.Text);// replaces the selected text with the text in the txtReplace textbox
                    frm1RTB.Focus();// focus on the form 1 rich text box
                }
            }
        }
        public void btnReplaceAll_Click(object sender, EventArgs e)//replaces all found instances of the found text with another text value
        {
            if (txtReplace.Text != "")// if the txtreplace text box has text in it
            {
                frm1RTB.Rtf = frm1RTB.Rtf.Replace(txtSearch.Text, txtReplace.Text);// replace all instances of the found text with the value in the txtReplace text box
            }
        }
        private void txtSearch_TextChanged(object sender, EventArgs e)// this event handler fires when the text in the txtSearch text box is changed
        {
            if (txtSearch.Text.Length > 0)// if the length of the text is greater than 0
            {
                btnFind.Enabled = true;// enable the find button
            }
            else if (txtSearch.Text.Length <= 0)// else if the length of the text in the txtSearch text box is less than or equal to 0
            {
                btnFind.Enabled = false;// disable the find button
                btnFindNext.Enabled = false;// disable the findNext button
            }
        }
    }
}// end of program