asp.net中文件如何上传到服务器上

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.IO;
namespace SuAn
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            if (this.filepost.PostedFile.FileName == "")
            {
                Response.Write("上传文件不能为空！");
                return;
            }
            try
            {
                string  Path = Server.MapPath("upload/");//设置服务器端路径
                string filePath = this.filepost.PostedFile.FileName;//获取客户端实际路径
                string fileName = filePath.Substring(filePath.LastIndexOf("\\")+1);//获取文件名称
                string serverPath = Path + fileName;//上传的文件保存到服务器端的路径
                System.Text.StringBuilder buider = new System.Text.StringBuilder();//上传的文件信息:可变字符串
                buider.Append("上传文件的类型:"+this.filepost.PostedFile.ContentType.ToString()+"");
                buider.Append("客户端文件地址："+this.filepost.PostedFile.FileName+"");
                buider.Append("上传文件名称："+fileName);
                buider.Append("上传文件的扩展名："+filePath.Substring(fileName.LastIndexOf(".")+1));
                buider.Append("上传文件的大小："+this.filepost.PostedFile.ContentLength/1024+"k"+"");
                if (System.IO.File.Exists(serverPath))
                {
                    Response.Write("这个文件在服务器上已经存在，请不要重复上传！");
                    return;
                }
                string str = fileName.Substring(fileName.LastIndexOf(".")+1);//获取文件后缀名
                if (str == "jpg" || str == "rar" || str == "ppt")
                {
                    Response.Write("对不起，该类型文件不能被上传！");
                    return;
                }
                if (this.filepost.PostedFile.ContentLength >2048)
                {
                    Response.Write("对不起，文件不能超过2K");
                    return;
                }
                this.filepost.PostedFile.SaveAs(serverPath);//上传保存文件
                this.lblMessage.Text = buider.ToString();
            }
            catch(Exception ex)
            {
                Response.Write(ex.Message);
            }
           
        }
    }
}