Right Click menu in richtextbox in C#

Add this code to your event....

        private void richTextBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == System.Windows.Forms.MouseButtons.Right)
            {
                ContextMenu contextMenu = new System.Windows.Forms.ContextMenu();
                MenuItem menuItem = new MenuItem("Cut");
                menuItem.Click += new EventHandler(CutAction);
                contextMenu.MenuItems.Add(menuItem);
                menuItem = new MenuItem("Copy");
                menuItem.Click += new EventHandler(CopyAction);
                contextMenu.MenuItems.Add(menuItem);
                menuItem = new MenuItem("Paste");
                menuItem.Click += new EventHandler(PasteAction);
                contextMenu.MenuItems.Add(menuItem);
                menuItem = new MenuItem("Select All");
                menuItem.Click += new EventHandler(SelectAll);
                contextMenu.MenuItems.Add(menuItem);
                richTextBox1.ContextMenu = contextMenu;
            }
        }

        void CutAction(object sender, EventArgs e)
        {
            richTextBox1.Cut();
        }

        void CopyAction(object sender, EventArgs e)
        {
            Clipboard.SetText(richTextBox1.SelectedText);
        }

        void PasteAction(object sender, EventArgs e)
        {
            if (Clipboard.ContainsText())
            {
                richTextBox1.Text += Clipboard.GetText(TextDataFormat.Text).ToString();
            }
        }

        void SelectAll(object sender, EventArgs e)
        {
           richTextBox1.SelectAll();
           richTextBox1.Focus();
        }