How to freeze Ctrl+C and Ctrl+V

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;

namespace test1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            pp();
        }
        private void pp()
        {
            string str = "DearSir,\nIn regard to your inqurey about....\nthanks";
            richTextBox1.Text=str;
        }
    }
}