C#获得程序的根目录以及判断文件是否存在的实例讲解

HttpContext.Current.Session["name"] = "猪八戒";
string name = HttpContext.Current.Request.Param["name"];
HttpContext.Current.Response.Write("猪八戒好吃懒做!");

Server.MapPath(Request.ServerVariables["PATH_INFO"])
Server.MapPath("/")
Server.MapPath("")
Server.MapPath(".")
Server.MapPath("../")
Server.MapPath("..") 
Page.Request.ApplicationPath

HttpContext.Current.Server.MapPath();
System.Web.HttpContext.Current.Request.PhysicalApplicationPath 

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;
 
public partial class Default3 : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {
   ShowPic.Visible = false;//初始化不显示
   ShowText.Visible = false;//初始化不显示
  }
  protected void Button1_Click(object sender, EventArgs e)
  {
 
   if (Directory.Exists(Server.MapPath("~/upimg/hufu")) == false)//如果不存在就创建file文件夹
   {
    Directory.CreateDirectory(Server.MapPath("~/upimg/hufu"));
   }
 
   //Directory.Delete(Server.MapPath("~/upimg/hufu"), true);//删除文件夹以及文件夹中的子目录，文件 
 
   //判断文件的存在
 
   if (File.Exists(Server.MapPath("~/upimg/Data.html")))
   {
    Response.Write("Yes");
 
    //存在文件
 
   }
 
   else
   {
    Response.Write("No");
    //不存在文件
    File.Create(MapPath("~/upimg/Data.html"));//创建该文件
 
   }
 
   string name = GetFiles.FileName;//获取已上传文件的名字
   string size = GetFiles.PostedFile.ContentLength.ToString();//获取已上传文件的大小
   string type = GetFiles.PostedFile.ContentType;//获取已上传文件的MIME
   string postfix = name.Substring(name.LastIndexOf(".") + 1);//获取已上传文件的后缀
   string ipath = Server.MapPath("upimg") +"\\"+ name;//获取文件的实际路径
   string fpath = Server.MapPath("upfile") + "\\" + name;
   string dpath = "upimg\\" + name;//判断写入数据库的虚拟路径
 
   ShowPic.Visible = true;//激活
   ShowText.Visible = true;//激活
 
   //判断文件格式
   if (name == "") { 
   Response.Write("<script>alert('上传文件不能为空')</script>");
   }
 
   else{
 
    if (postfix == "jpg" || postfix == "gif" || postfix == "bmp" || postfix == "png")
    {
     GetFiles.SaveAs(ipath);
     ShowPic.ImageUrl = dpath;
     ShowText.Text = "你上传的图片名称是:" + name + "<br>" + "文件大小:" + size + "KB" + "<br>" + "文件类型:" + type + "<br>" + "存放的实际路径为:" + ipath;
 
    }
 
    else
    {
     ShowPic.Visible = false;//隐藏图片
     GetFiles.SaveAs(fpath);//由于不是图片文件,因此转存在upfile这个文件夹
     ShowText.Text = "你上传的文件名称是:" + name + "<br>" + "文件大小:" + size + "KB" + "<br>" + "文件类型:" + type + "<br>" + "存放的实际路径为:" + fpath;
 
    }
 
   
   }
 
 
  }
}