C#中openFileDialog控件的使用方法

//使用 OpenFile 从筛选的选择中打开文件
using System.Diagnostics;
using System.Security;
 
namespace WinFormsApp1
{
    public partial class OpenFileDialogForm : Form
    {
        private readonly Button selectButton;
        private readonly OpenFileDialog openFileDialog1;
 
        public OpenFileDialogForm()
        {
            InitializeComponent();
 
            //新建openFileDialog控件
            openFileDialog1 = new OpenFileDialog()
            {
                FileName = "Select a text file",      //OpenFileDialog窗体提示
                Filter = "Text files (*.txt)|*.txt",  //选择什么扩展名类型的文件
                Title = "Open text file"              //OpenFileDialog窗体的抬头
            };
 
            //新建按钮及点击事件
            selectButton = new Button()
            {
                Size = new Size(100, 20),
                Location = new Point(15, 15),
                Text = "Select file"
            };
            selectButton.Click += new EventHandler(SelectButton_Click);
            Controls.Add(selectButton);
        }
 
        /// <summary>
        /// 按钮点击事件应用
        /// 使用 Button 控件的 Click 事件处理程序打开包含仅显示文本文件的筛选器的 OpenFileDialog。 
        /// 用户选择文本文件并选择“确定”后，可用 OpenFile 方法在记事本中打开该文件
        /// </summary>
        private void SelectButton_Click(object? sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    var filePath = openFileDialog1.FileName;
                    using Stream str = openFileDialog1.OpenFile();
                    Process.Start("notepad.exe", filePath);
                }
                catch (SecurityException ex)
                {
                    MessageBox.Show($"Security error.\n\nError message: {ex.Message}\n\n" +
                    $"Details:\n\n{ex.StackTrace}");
                }
            }
        }
    }
}

//使用 StreamReader 以流的形式读取文件
using System.Security;
namespace _05_3
{
    public partial class Form1 : Form
    {
        private readonly Button selectButton;
        private readonly OpenFileDialog openFileDialog1;
        private readonly TextBox textBox1;
 
        public Form1()
        {
            InitializeComponent();
 
            //创建OpenFileDialog控件openFileDialog1
            openFileDialog1 = new OpenFileDialog();
 
            //创建按钮控件selectButton及添加点击事件
            selectButton = new Button
            {
                Size = new Size(100, 20),
                Location = new Point(15, 15),
                Text = "Select file"
            };
            selectButton.Click += new EventHandler(SelectButton_Click);
 
            //创建文本框控件textBox1
            textBox1 = new TextBox
            {
                Size = new Size(300, 300),
                Location = new Point(15, 40),
                Multiline = true,
                ScrollBars = ScrollBars.Vertical
            };
 
            //设置Form1表格大小
            ClientSize = new Size(330, 360);
 
            Controls.Add(selectButton);
            Controls.Add(textBox1);
        }
 
        //自定义方法
        private void SetText(string text)
        {
            textBox1.Text = text;
        }
 
        /// <summary>
        /// 使用 StreamReader 以流的形式读取文件
        /// 使用 Windows 窗体 Button 控件的 Click 事件处理程序通过 ShowDialog 方法打开 OpenFileDialog。
        /// 用户选择一个文件并选择“确定”后，StreamReader 类的实例将读取该文件，并在窗体的文本框中显示文件内容。
        /// </summary>
        private void SelectButton_Click(object? sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    var sr = new StreamReader(openFileDialog1.FileName);
                    SetText(sr.ReadToEnd());
                }
                catch (SecurityException ex)
                {
                    MessageBox.Show($"Security error.\n\nError message: {ex.Message}\n\n" +
                    $"Details:\n\n{ex.StackTrace}");
                }
            }
        }
    }
}