C#实现文件上传进度条

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;

public partial class FileProcessBar : System.Web.UI.Page
{
    
    
    // determin how often Progress Info will be refreshed 
    const int RefreshTime = 0;

    // determine, which panel to show 
    public enum PageMode { UploadForm, Uploading, Result }
    public PageMode pageMode
    {
        get
        {
            object o = ViewState["pageMode"];
            return (o == null) ? PageMode.UploadForm : (PageMode)o;
        }
        set
        {
            ViewState["pageMode"] = value;
            switch (value)
            {
                case PageMode.UploadForm: panResult.Visible = panInfo.Visible = !(panUpload.Visible = true); break;
                case PageMode.Uploading:
                    // initialize fields 
                    litRefreshJS.Text = String.Format("<script>setTimeout(\"{0}\", {1});</script>", ClientScript.GetPostBackEventReference( btnRefresh, ""), RefreshTime);
                    panResult.Visible = panUpload.Visible = !(panInfo.Visible = true);
                    panProgressBar.Width = 0;
                    break;
                case PageMode.Result:
                    // result information 
                    litRefreshJS.Text = "";
                    Session.Remove("FileUploadThread");
                    panUpload.Visible = panInfo.Visible = !(panResult.Visible = true);
                    break;
            }
        }
    }

    // how many bytes has been uploaded. 
    public long BytesRead
    {
        get { object o = ViewState["BytesRead"]; return (o == null) ? 0 : (long)o; }
        set { ViewState["BytesRead"] = value; }
    } 

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            if (Session["FileUploadThread"] != null)
            {
                // this users has the session, possible there‘s an unfinished file upload 
                lblResult.Text = "文件正在上载过程中……";
                litRefreshJS.Text = "";
                pageMode = PageMode.Result;
            }
            else pageMode = PageMode.UploadForm;
        }
    }
    protected void btnUpload_Click(object sender, EventArgs e)
    {
        if (theFile.PostedFile.ContentLength == 0) return;

        lblFilename.Text = Path.GetFileName(theFile.PostedFile.FileName);
        lblProgress.Text = String.Format("{0} of {1} bytes (0 %)", 0, theFile.PostedFile.InputStream.Length);

        string dir = MapPath("files/");
        if (!Directory.Exists(dir)) Directory.CreateDirectory(dir);

        Session["FileUploadThread"] = new FileUploadThread(dir + lblFilename.Text, theFile.PostedFile.InputStream);
        pageMode = PageMode.Uploading; 
    }
    protected void btnCancel_Click(object sender, EventArgs e)
    {
        FileUploadThread fut = (FileUploadThread)Session["FileUploadThread"];
        if (fut != null) fut.Cancel();
        

        lblResult.Text = "上载文件已经被取消！";
        pageMode = PageMode.Result; 
    }
    protected void btnRefresh_Click(object sender, EventArgs e)
    {
        FileUploadThread fut = (FileUploadThread)Session["FileUploadThread"];

        if (!fut.Uploaded)
        {
            litRefreshJS.Text = String.Format("<script>setTimeout(\"{0}\", {1});</script>", ClientScript.GetPostBackEventReference(btnRefresh, ""), RefreshTime);
            lblProgress.Text = String.Format("{0} of {1} bytes ({2} %)", fut.BytesRead,fut.Length,fut.Percent);
            panProgressBar.Width = 2 * fut.Percent;
            panProgressBar.Height = 20;

        }
        else
        {
            if (fut.Exception == null)
                lblResult.Text = String.Format("\"<a href=‘files/{0}‘>{0}</a>\" 文件上载成功！<br/>文件是：{1}<br/>描述是：{2}", lblFilename.Text, (chbImportant.Checked) ? "重要的" : "不重要的", edInfo.Text);
            else
                lblResult.Text = String.Format("上载文件错误，错误信息如下： {0}<br>{1}", fut.Exception.GetType(), fut.Exception.Message);

            pageMode = PageMode.Result;
        } 
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Threading;
using System.IO;

/// <summary>
///FileUploadThread 的摘要说明
/// </summary>
public class FileUploadThread
{
    private string _filename;
    private Stream _stream;
    private bool _uploaded;
    private Exception _exception;
    private Thread _tID;
    private int _bytesRead;
    private int _length;
    private int  _percent;

    public FileUploadThread(string filename,Stream stream)
	{
		//
		//TODO: 在此处添加构造函数逻辑
		//
        _filename = filename;
        _stream = stream;
        _length = (int)_stream.Length;
        _uploaded = false;
        _exception = null;
        _tID = new Thread(new ThreadStart(uploadThread));
        _tID.Start();
        
	}
    public void Cancel()
    {
    }

    public bool Uploaded
    {
        get { return _uploaded; }
        set { _uploaded = value; }
    }

    public Exception Exception
    {
        get { return _exception; }
        set { _exception = value; }
    }

    public int BytesRead
    {
        get { return _bytesRead; }
        set { _bytesRead = value; }
    }
    public int Length
    {
        get { return _length ; }
        set { _length  = value; }
    }
    public int  Percent
    {
        get { return _percent ; }
        set { _percent  = value; }
    }
    private void uploadThread()
    {
        byte[] b=new byte[1024];
        int read = 0;
     
        try
        {
            using (FileStream fs=new FileStream(_filename,FileMode.Create ))
            {

                while((read=_stream.Read(b,0,b.Length ))>0)
                {
                    fs.Write(b,0,read );
                    _bytesRead+=read ;
                    _percent = (int)(_bytesRead*100 /_length);
                    System.Threading.Thread.Sleep(1000);
                }

            }
        }
        catch(Exception ex){_exception=ex;}
        _uploaded=true ;
    }
}