打开文件对话框

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;
using System.IO;
using System.Security;

namespace OpenFile
{
    public partial class OpenFileDialogForm : Form
    {
        // 字段
        private Button selectButton; // 按钮
        private OpenFileDialog openFileDialog1; // 打开文件对话框    
        private TextBox textBox1; // 文本编辑框

        //窗体构造函数
        public OpenFileDialogForm()
        {         
            //新建打开文件对话框
            openFileDialog1 = new OpenFileDialog();

            //新建按钮
            selectButton = new Button
            {
                Size = new Size(100, 20),
                Location = new Point(15, 15),
                Text = "Select file"
            };
            
            //添加, 按钮Click事件处理
            selectButton.Click += new EventHandler(SelectButton_Click);

            //新建文本编译框
            textBox1 = new TextBox
            {
                Size = new Size(300, 300),
                Location = new Point(15, 40),
                Multiline = true,
                ScrollBars = ScrollBars.Vertical
            };
            
            //窗体大小
            ClientSize = new Size(330, 360);
            
            //窗体容器, 添加按钮、文本编译框
            Controls.Add(selectButton);
            Controls.Add(textBox1);
        }

        //文本复制
        private void SetText(string text)
        {
            textBox1.Text = text;
        }

        //按钮Click事件处理函数
        private void SelectButton_Click(object sender, EventArgs e)
        {
            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                try
                {
                    //新建读取文件流对象
                    var sr = new StreamReader(openFileDialog1.FileName);
                    //文本复制
                    SetText(sr.ReadToEnd());
                }
                catch (SecurityException ex)
                {
                    MessageBox.Show("Security error.

Error message: {ex.Message}

" +
                    "Details:

{ex.StackTrace}");
                }
            }
        }
    }
}