Code example of Winform OpenFileDialog pop-up file dialog box

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

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

    /// <summary>
    /// 打开文件按钮单击事件
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void btn_OpenFile_Click(object sender, EventArgs e)
    {
      //定义一个文件打开控件
      OpenFileDialog ofd = new OpenFileDialog();
      //设置打开对话框的初始目录，默认目录为exe运行文件所在的路径
      ofd.InitialDirectory = Application.StartupPath;
      //设置打开对话框的标题
      ofd.Title = "请选择要打开的文件";
      //设置打开对话框可以多选
      ofd.Multiselect = true;
      //设置对话框打开的文件类型
      ofd.Filter = "文本文件|*.txt|音频文件|*.wav|图片文件|*.jpg|所有文件|*.*";
      //设置文件对话框当前选定的筛选器的索引
      ofd.FilterIndex = 2;
      //设置对话框是否记忆之前打开的目录
      ofd.RestoreDirectory = true;
      if (ofd.ShowDialog() == DialogResult.OK)
      { 
        //获取用户选择的文件完整路径
        string filePath = ofd.FileName;
        //获取对话框中所选文件的文件名和扩展名，文件名不包括路径
        string fileName = ofd.SafeFileName;       
        OutLog("用户选择的文件目录为:" + filePath);
        
        OutLog("用户选择的文件名称为:"+fileName);
        OutLog("**************选中文件的内容**************");
        using (FileStream fsRead = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.Read))
        { 
         //定义二进制数组
          byte[] buffer = new byte[1024 * 1024 * 5];
          //从流中读取字节
          int r= fsRead.Read(buffer, 0, buffer.Length);
          OutLog(Encoding.Default.GetString(buffer,0,r));
        }
      }
    }

    /// <summary>
    /// 输出日志
    /// </summary>
    /// <param name="strLog"></param>
    private void OutLog(string strLog)
    {
      //如果日志信息长度超过1000行，则自动清空
      if (txt_FileInfo.GetLineFromCharIndex(txt_FileInfo.Text.Length) > 1000)
      {
        //清空文本
        txt_FileInfo.Clear();
      }
      txt_FileInfo.AppendText(DateTime.Now.ToString("HH:mm:ss ")+strLog+"\r\n");
    }
  }
}