如何实现大文件数据上传

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

namespace WinShowDown
{
public partial class FrmMain : Form
{
public FrmMain()
{
InitializeComponent();
}

private void btnDown_Click(object sender, EventArgs e)
{
DownloadFile("http://localhost:1928/WebServer/downloader/123.rar", @"C:\123.rar", progressBar1, label1);
}
/// <summary>
/// c#,.net 下载文件
/// </summary>
/// <param name="URL">下载文件地址</param>
///
/// <param name="Filename">下载后的存放地址</param>
/// <param name="Prog">用于显示的进度条</param>
///
public void DownloadFile(string URL, string filename, System.Windows.Forms.ProgressBar prog, System.Windows.Forms.Label label1)
{
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 = "当前补丁下载进度" + percent.ToString() + "%";
System.Windows.Forms.Application.DoEvents(); //必须加注这句代码，否则label1将因为循环执行太快而来不及显示信息
}
so.Close();
st.Close();
}
catch (System.Exception)
{
throw;
}
}
}
}