Notepad (improved but not yet complete)

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

namespace _6._30_dialog
{
    public partial class Form1: Form
    {
        public Form1 ()
        {
            InitializeComponent ();
        }
        private void exit XToolStripMenuItem_Click (object sender, EventArgs e)
        {
            this.Close (); // Close the window
        }

        private void undo UToolStripMenuItem_Click (object sender, EventArgs e)
        {
            textBox1.Undo (); // Undo the last operation in textBox1

        }

        private void cut TToolStripMenuItem_Click (object sender, EventArgs e)
        {
            textBox1.Cut (); // Cut--Move the selection in textBox1 to the clipboard
        }

        private void copy CToolStripMenuItem_Click (object sender, EventArgs e)
        {
            textBox1.Copy (); // Copy--copy the selected content in textBox1 to the clipboard
        }

        private void paste PToolStripMenuItem_Click (object sender, EventArgs e)
        {
            textBox1.Paste (); // Paste--Replace the selected content in textBox1 with the content in the clipboard
        }

        private void Select all AToolStripMenuItem_Click (object sender, EventArgs e)
        {
            textBox1.SelectAll (); // Select all content in textBox1
        }

        private void textBox1_TextChanged (object sender, EventArgs e)
        {
            string num = textBox1.TextLength.ToString (); // Number of words in textBox1
            zishu.Text = num; // Word count display
        }

        private void font ToolStripMenuItem_Click (object sender, EventArgs e)
        {
            fontDialog1.ShowColor = true; // display color
            fontDialog1.ShowDialog (); // open
            textBox1.Font = fontDialog1.Font; // font change
            textBox1.ForeColor = fontDialog1.Color; // color change
        }

        private void Open OToolStripMenuItem_Click (object sender, EventArgs e)
        {
            openFileDialog1.Filter = "Text file | * .txt"; // Restrict display of open file types
            DialogResult dr = openFileDialog1.ShowDialog ();

            if (dr == DialogResult.OK) // Click OK
            {
                StreamReader sr = new StreamReader (openFileDialog1.FileName, UnicodeEncoding.GetEncoding ("GB2312"));
                textBox1.Text = sr.ReadToEnd ();
                sr.Close (); // Close the flow channel
            }
        }
        string path = "";
        private void save SToolStripMenuItem_Click (object sender, EventArgs e)
        {
            if (path == "") // whether it has been saved
            {
                saveFileDialog1.FileName = "New Text File.txt";
                saveFileDialog1.ShowDialog ();
                path = saveFileDialog1.FileName;
            }
            StreamWriter sw = new StreamWriter (path);
            sw.Write (textBox1.Text);
            sw.Close ();
        }

        private void Save as AToolStripMenuItem_Click (object sender, EventArgs e)
        {
            saveFileDialog1.FileName = "New Text File.txt";
            saveFileDialog1.ShowDialog ();
            path = saveFileDialog1.FileName;
            StreamWriter sw = new StreamWriter (path);
            sw.Write (textBox1.Text);
            sw.Close ();
        }

        private void print settings ToolStripMenuItem_Click (object sender, EventArgs e)
        {
            pageSetupDialog1.Document = printDocument1; // The setting object to be printed is printDocument1
            pageSetupDialog1.ShowDialog (); // Open dialog
        }

        private void printDocument1_PrintPage (object sender, System.Drawing.Printing.PrintPageEventArgs e)
        {// print object
            Font f = new Font ("宋体", 14); // font format
            Brush b = new SolidBrush (Color.Black); // The filled foreground color is black
            PointF p = new PointF (10, 10); // Start printing position

            e.Graphics.DrawString (textBox1.Text, f, b, p);
           // e.Graphics.DrawString (string to be drawn, text format of the string, color and texture of the drawn text, upper left corner of the drawn text)
        }

        private void print preview VToolStripMenuItem_Click (object sender, EventArgs e)
        {
            printPreviewDialog1.Document = printDocument1; // The print preview object is printDocument1
            printPreviewDialog1.ShowDialog ();
        }

        private void print PToolStripMenuItem_Click (object sender, EventArgs e)
        {
            printDialog1.Document = printDocument1; // The object to be printed is printDocument1
            printDialog1.ShowDialog ();
        }
    }
} 

Notepad (improved but not yet complete)