C#写一个简单的记事本功能

以下是一个简单的记事本功能的 C# 代码示例：

using System;
using System.IO;
using System.Windows.Forms;

namespace Notepad
{
    public partial class Form1 : Form
    {
        string filePath = "";

        public Form1()
        {
            InitializeComponent();
        }

        private void NewFile()
        {
            if (textBox1.Text.Length > 0)
            {
                DialogResult result = MessageBox.Show("Do you want to save changes to this file?", "Notepad", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);

                if (result == DialogResult.Yes)
                {
                    Save();
                }
                else if (result == DialogResult.Cancel)
                {
                    return;
                }
            }

            textBox1.Text = "";
            filePath = "";
        }

        private void Open()
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = "Text Files (*.txt)|*.txt|All Files (*.*)|*.*";

            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                using (StreamReader reader = new StreamReader(openFileDialog.FileName))
                {
                    textBox1.Text = reader.ReadToEnd();
                    filePath = openFileDialog.FileName;
                }
            }
        }

        private void Save()
        {
            if (filePath.Length > 0)
            {
                using (StreamWriter writer = new StreamWriter(filePath))
                {
                    writer.Write(textBox1.Text);
                }
            }
            else
            {
                SaveFileDialog saveFileDialog = new SaveFileDialog();
                saveFileDialog.Filter = "Text Files (*.txt)|*.txt|All Files (*.*)|*.*";

                if (saveFileDialog.ShowDialog() == DialogResult.OK)
                {
                    using (StreamWriter writer = new StreamWriter(saveFileDialog.FileName))
                    {
                        writer.Write(textBox1.Text);
                        filePath = saveFileDialog.FileName;
                    }
                }
            }
        }

        private void SaveAs()
        {
            SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = "Text Files (*.txt)|*.txt|All Files (*.*)|*.*";

            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                using (StreamWriter writer = new StreamWriter(saveFileDialog.FileName))
                {
                    writer.Write(textBox1.Text);
                    filePath = saveFileDialog.FileName;
                }
            }
        }

        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (textBox1.Text.Length > 0)
            {
                DialogResult result = MessageBox.Show("Do you want to save changes to this file?", "Notepad", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);

                if (result == DialogResult.Yes)
                {
                    Save();
                }
                else if (result == DialogResult.Cancel)
                {
                    e.Cancel = true;
                }
            }
        }

        private void newToolStripMenuItem_Click(object sender, EventArgs e)
        {
            NewFile();
        }

        private void openToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Open();
        }

        private void saveToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Save();
        }

        private void saveAsToolStripMenuItem_Click(object sender, EventArgs e)
        {
            SaveAs();
        }

        private void exitToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Close();
        }
    }
}

这个记事本应用程序基于 Windows 窗体，包括菜单栏、工具栏和一个文本框用于编辑文本。它支持新建、打开、保存、另存为和退出功能。它使用 OpenFileDialog 和 SaveFileDialog 对话框来打开和保存文件。在关闭应用程序时，如果存在未保存的更改，会提示用户保存更改。