【C#】完成下載進圖條實現

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;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnDown_Click(object sender, EventArgs e)
        {
            DownloadFile("http://Client-8.7.2.exe", @"C:\\Users\yf\\Desktop\\Client.exe", progressBar1);
        }

        public void DownloadFile(string URL, string filename, System.Windows.Forms.ProgressBar prog)
        {
            float percent = 0;

            try
            {
                System.Net.HttpWebRequest Myrq = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(URL);
                System.Net.HttpWebResponse Myrp = (System.Net.HttpWebResponse)Myrq.GetResponse();
                long totalBytes = Myrp.ContentLength;
                if (prog != null)
                {
                    prog.Maximum = (int)totalBytes;
                }
                System.IO.Stream st = Myrp.GetResponseStream();
                System.IO.Stream so = new System.IO.FileStream(filename, System.IO.FileMode.Create);
                long totalDownloadedByte = 0;
                byte[] by = new byte[1024];
                int osize = st.Read(by, 0, (int)by.Length);
                while (osize > 0)
                {
                    totalDownloadedByte = osize + totalDownloadedByte;
                    System.Windows.Forms.Application.DoEvents();
                    so.Write(by, 0, osize);
                    if (prog != null)
                    {
                        prog.Value = (int)totalDownloadedByte;
                    }
                    osize = st.Read(by, 0, (int)by.Length);

                    percent = (float)totalDownloadedByte / (float)totalBytes * 100;
                    label1.Text = percent.ToString() + "%";
                    System.Windows.Forms.Application.DoEvents();
                }
                so.Close();
                st.Close();
            }
            catch(System.Exception)
            {
                throw;
            }
        }

        private void ProgressBar_Value(int val)
        {
            progressBar1.Value = val;
            label1.Text = val.ToString() + "%";
        }

    }
}