Search_Highlight text in TextBox or RichTextBox in Window Application

Step 1: Form

Drag and down a TextBox and a button (Search).

Step 2: Code

Double click on Search Button and write this code.

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

using System.Data.SqlClient;

using System.Text;


namespace First_Csharp_app


    public partial class Form1 : Form


        public Form1()




        private void Button1_click(object sender, EventArgs e)


            Stream mystream;

            OpenFileDialog openfile = new OpenFileDialog ();

            if(openfile .ShowDialog() ==System.Window.Forms.DialogResult.OK)


                if((mystream = openfile .OpenFile() ) ! = null)

                string strfilename = openfile .FileName;

                String filetext = File.ReadAllText(strfilename);

                richTextBox1.text = filetext;




        private void Search_btn_click(object sender, EventArgs e)


            //Searches the text in a RichTextbox control for a string within a range of text Within.

            richTextBox1.text.Find(textBox1.Text , index , richTextBox1.TextLength, RichTextBoxFinds.None);

            //Selection Colour

            richTextBox1.selectionBackColour = Color.Red;

            //After a match is found the index is increased so the search won't stop at the same name.

            index = tichTextBox1.Text.IndexOf(textBox1.Text , index) +1;




Step 3: Run

Now run your application and put a text in TextBox and click on search button.

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