//写入

    protected void Button2_Click(object sender, EventArgs e)
     {
         HttpCookie cookie=new HttpCookie("MyCook");//初使化并设置Cookie的名称
         DateTime dt=DateTime.Now;
         TimeSpan ts = new TimeSpan(0, 0, 1,0,0);//过期时间为1分钟
         cookie.Expires = dt.Add(ts);//设置过期时间
         cookie.Values.Add("userid", "userid_value");
         cookie.Values.Add("userid2","userid2_value2");
         Response.AppendCookie(cookie);
        //输出该Cookie的所有内容
        //Response.Write(cookie.Value); //输出为：userid=userid_value&userid2=userid2_value2 
     }
    //读取
    protected void Button1_Click(object sender, EventArgs e)
     {
       // HttpCookie cokie = new HttpCookie("MyCook");//初使化
        if (Request.Cookies["MyCook"]!=null)
         {
            //Response.Write("Cookie中键值为userid的值:" + Request.Cookies["MyCook"]["userid"]);//整行
            //Response.Write("Cookie中键值为userid2的值" + Request.Cookies["MyCook"]["userid2"]);
             Response.Write(Request.Cookies["MyCook"].Value);//输出全部的值
         }
     }

    //修改Cookie
    protected void Button3_Click(object sender, EventArgs e)
     {
        //获取客户端的Cookie对象
         HttpCookie cok = Request.Cookies["MyCook"];
        
        if (cok != null)
         {
         //修改Cookie的两种方法
             cok.Values["userid"] = "alter-value";
             cok.Values.Set("userid", "alter-value");
          //往Cookie里加入新的内容
              cok.Values.Set("newid", "newValue");
              Response.AppendCookie(cok);
         }
      
     }
    //删除Cookie
    protected void Button4_Click(object sender, EventArgs e)
     {
         HttpCookie cok = Request.Cookies["MyCook"];
        if (cok != null)
         {
            if (!CheckBox1.Checked)
             {
                 cok.Values.Remove("userid");//移除键值为userid的值
             }
            else
             {
                 TimeSpan ts = new TimeSpan(-1, 0, 0, 0);
                 cok.Expires = DateTime.Now.Add(ts);//删除整个Cookie，只要把过期时间设置为现在
             }
             Response.AppendCookie(cok);
         }
     }

asp.net cookie的操作