FileStream读取文件 案例（复制）

             // FileStream针对操作"字节"
            //StreamReader 和 StreamWriter是针对"字符"进行操作的


            string str = string.Empty;
            using (FileStream ss = new FileStream(@"C:UsersAdministratorDesktopa.txt", FileMode.OpenOrCreate, FileAccess.Read))
            {//PC不会自己进行释放，需要借助using
                byte[] bb = new byte[1024 * 1024 * 5];//缓冲区的大小
                int a = ss.Read(bb, 0, bb.Length);//实际写入缓冲区的大小
                str = Encoding.Default.GetString(bb, 0, a);//进行读取
            }
            Console.WriteLine(str);
            Console.ReadKey();

案例图片（winform）

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;

namespace WindowsFormsApplication6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Title = "请选择要复制的文件";
            ofd.InitialDirectory = @"C:UsersAdministratorDesktop";
            ofd.Filter = "所有文件|*.*";
            ofd.ShowDialog();
            textBox1.Text = ofd.FileName;
        }

        private void button2_Click(object sender, EventArgs e)
        {
            SaveFileDialog s = new SaveFileDialog();
            s.Title = "请选择要保存文件的路径";
            s.InitialDirectory = @"C:UsersAdministratorDesktop";
            s.ShowDialog();
            textBox2.Text = s.FileName;//获取最终保存的文件路径和名称
            using (FileStream fread = new FileStream(textBox1.Text.Trim(), FileMode.OpenOrCreate, FileAccess.Read))
            {//先读取，再写出，此处为读取
                using (FileStream fwrite = new FileStream(textBox2.Text.Trim(), FileMode.OpenOrCreate, FileAccess.Write))
                {//此处为写出

                    //设置进度条的最大值
                    progressBar1.Maximum = (int)fread.Length;
                    byte[] bb = new byte[1024 * 1024 * 5];//设定缓冲池的大小
                    while (true)
                    {
                        //按照缓冲池的大小读取文件内容，a为实际读取的大小
                        int a = fread.Read(bb, 0, bb.Length);
                        if (a == 0)
                        {
                            break;
                        }
                        //根据缓冲池读取的实际大小来输出
                        fwrite.Write(bb,0,a);
                        //设置进度条的进度
                        progressBar1.Value = (int)fread.Length;
                    }
                    MessageBox.Show("复制成功");
                }
            }



         

        }
    }
}