打开与保存文件 - (第三十六讲)

视频讲解如下：

源码下载，提取码：fyi3

https://pan.baidu.com/s/1OvRbkERvHJCjX0Mpla8zEw 

下面演示在WinForm环境下如何实现文件的打开、保存、另存，三种操作的。

首先呢，需要在工具栏里面添加openFileDialog控件。

演示效果如下

演示代码如下

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

namespace WindowsFormsApp
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        /// <summary>
        /// 判断文件格式
        /// </summary>
        /// <param name="filePath"></param>
        /// <returns></returns>
        private bool IsAllowedExtension(string filePath)
        {
            FileStream stream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
            BinaryReader reader = new BinaryReader(stream);
            string fileclass = "";
            try
            {
                for (int i = 0; i < 2; i++)
                {
                    fileclass += reader.ReadByte().ToString();
                }
            }
            catch
            {
                stream.Close();
                throw;
            }
            if (fileclass == "230191" || fileclass == "239187")
            {
                stream.Close();
                return true;
            }
            else
            {
                stream.Close();
                return false;
            }
        }

        /// <summary>
        /// 读取文件
        /// </summary>
        /// <param name="path"></param>
        /// <returns></returns>
        public byte[] ReadFile(string path)
        {
            try
            {
                if (path == "") return null;
                if (File.Exists(path))
                {
                    if (true == IsAllowedExtension(path))
                    {
                        try
                        {
                            using (FileStream fs = new FileStream(path, FileMode.Open))
                            {
                                byte[] arrFile = new byte[30000];
                                int num = 29999;
                                int length = fs.Read(arrFile, 0, arrFile.Length);
                                if (length != 0)
                                {
                                    while ((arrFile[num] == 0x00) && (num > 0)) num--;
                                    byte[] oData = new byte[num + 1];
                                    Array.Copy(arrFile, oData, num + 1);
                                    if (oData.Length == 0) return null;
                                    return oData;
                                }
                            }
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine(ex.Message);
                        }
                    }
                }
            }
            catch { }
            return null;
        }

        /// <summary>
        /// 打开文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button1_Click(object sender, EventArgs e)
        {
            this.openFileDialog1.FileName = "";
            this.openFileDialog1.Filter = "*.txt|*.txt|所有文件(*.*)|*.*";
            if (this.openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox2.Text = this.openFileDialog1.FileName;
                // 读取文件
                byte[] arrFile = ReadFile(this.openFileDialog1.FileName);
                // Byte[] 转 string
                textBox1.Text = System.Text.Encoding.UTF8.GetString(arrFile);
            }
        }

        /// <summary>
        /// 保存文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button2_Click(object sender, EventArgs e)
        {
            // 第二个参数：false是覆盖保存，true是追加保存
            StreamWriter sw = new StreamWriter(textBox2.Text, false, Encoding.UTF8);
            sw.Write(textBox1.Text);
            sw.Close();
            MessageBox.Show("保存成功！", "提示");
        }

        /// <summary>
        /// 另存文件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void button3_Click(object sender, EventArgs e)
        {
            Stream myStream;
            SaveFileDialog saveFileDialog1 = new SaveFileDialog();
            saveFileDialog1.Filter = "txt files   (*.txt)|*.txt";
            saveFileDialog1.FilterIndex = 2;
            saveFileDialog1.RestoreDirectory = true;
            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                if ((myStream = saveFileDialog1.OpenFile()) != null)
                {
                    using (StreamWriter sw = new StreamWriter(myStream))
                    {
                        sw.Write(textBox1.Text);
                    }
                    myStream.Close();
                    MessageBox.Show("保存成功！", "提示");
                }
            }
        }
    }
}

另一种保存文件的方式

/// <summary>
/// 另一种保存文件的方式（追加写）
/// </summary>
/// <param name="data"></param>
public void WriteFile(string data)
{
    try
    {
        if (!Directory.Exists(Environment.CurrentDirectory))
        {
            Directory.CreateDirectory(Environment.CurrentDirectory);
        }
        string FileName = Environment.CurrentDirectory + DateTime.Now.ToString("yyyyMMddhh") + "_log.txt";
        using (StreamWriter file = new StreamWriter(FileName, true))
        {
            file.Write(data);
            file.Close();
        }  
    }
    catch { }
}