//form1.cs
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;

namespace Txt_EditApp
{
 public partial class Form1 : Form
 {
  public Form1()
  {
   InitializeComponent();
  }
  //Open file 菜單選項
  private void openFileToolStripMenuItem_Click(object sender, EventArgs e)
  {
   openFileDialog1.Filter = "txt files(*.txt)|*.txt";
   if(openFileDialog1.ShowDialog()==DialogResult.OK)
   {
    richTextBox1.LoadFile(openFileDialog1.FileName, RichTextBoxStreamType.PlainText);
   }
  }
  //Save file 菜單選項
  private void saveFileToolStripMenuItem_Click(object sender, EventArgs e)
  {
   saveFileDialog1.Filter = "txt files(*.txt)|*.txt";
   if(saveFileDialog1.ShowDialog()==DialogResult.OK)
   {
    richTextBox1.SaveFile(saveFileDialog1.FileName, RichTextBoxStreamType.PlainText);
   }
  }
  //exit file 菜單選項
  private void exitToolStripMenuItem_Click(object sender, EventArgs e)
  {
   Close();
  }
  //About 菜單選項
  private void aboutToolStripMenuItem_Click(object sender, EventArgs e)
  {
   Form2 frm = new Form2();
   frm.ShowDialog();
  }
 }
}


//form2.cs
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;

namespace Txt_EditApp
{
 public partial class Form2 : Form
 {
  public Form2()
  {
   InitializeComponent();
  }

  private void label2_Click(object sender, EventArgs e)
  {

  }
 }
}