主题：关于被教程一笔带过的内容

Static UserTable As DataTable '定义一个变量,用于存储用户随机身份ID,以及最后一次活动时间.
Static ClearTime As Date
If UserTable Is Nothing Then '创建用于记录登录信息的临时表
    ClearTime = Date.Now()
    Dim dtb As New DataTableBuilder("UserInfos")
    dtb.AddDef("UserName", Gettype(String), 16)
    dtb.AddDef("UserID",Gettype(String),16)
    dtb.AddDef("ActiveTime",Gettype(Date))
    UserTable = dtb.Build(True)
End If
If (Date.Now - ClearTime).TotalMinutes >= 30 Then '清除超过30分钟没有操作的登录信息
    UserTable.DeleteFor("ActiveTime < #" & Date.Now.AddMinutes(-30) & "#")
    ClearTime = Date.Now()
End If
Dim wb As New weui
'身份验证
Dim UserName As String
Dim Password As String
Dim UserID As String
If e.Path = "logon.htm" '验证用户名和密码
    If e.PostValues.ContainsKey("username") AndAlso e.PostValues.ContainsKey("password")  Then
        Dim Verified As Boolean '用于标记用户是否通过了身份验证
        UserName = e.PostValues("username")
        Password = e.PostValues("password")
        If UserName = "张三" AndAlso Password = "888" Then  '实际使用的时候,请改为从数据库读取用户名和密码进行比较
            Verified  = True
        ElseIf Username = "李四" AndAlso Password="999" Then
            Verified  = True
        End If
        If Verified Then
            UserID = Rand.NextString(16) '生成随机用户ID
            UserName = EncryptText(UserName,"123","123") '将用户名加密.
            Dim dr As DataRow = UserTable.Find("UserName = '" & UserName & "'")
            If  dr IsNot Nothing Then '如果是重复登录,删除以前的登录信息
                dr.Delete()
            End If
            dr = UserTable.AddNew()
            dr("UserName") = UserName
            dr("UserID") = UserId
            dr("ActiveTime") = Date.Now '记录登录时间
            wb.AppendCookie("username",UserName) '将用户名和密码写入cookie
            wb.AppendCookie("userid",UserID)
            wb.InsertHTML("<meta http-equiv='Refresh' c>") '直接跳转到首页
            e.WriteString(wb.Build) '生成网页
            Return '必须的
        End If
    End If
Else '其它页面从Cookie提取登录信息进行验证
    UserName = e.Cookies("username")  '从cookie中获取用户名
    UserID = e.Cookies("userid")  '从cookie中获取 随机ID
    Dim dr As DataRow = UserTable.Find("UserName = '" & UserName & "'")
    If dr IsNot Nothing AndAlso dr("UserID") = UserID Then  '如果通过验证,更新活动时候,继续访问其它页面.
        dr("ActiveTime") = Date.Now '更新活动时间
    Else '如果验证失败
        wb.InsertHTML("<meta http-equiv='Refresh' c>") '那么直接跳转到登录页面
        e.WriteString(wb.Build) '生成网页
        Return '必须的
    End If
End If
'开始生成网页
Select Case e.path
    Case "logon.htm" '登录页面
        wb.AddPageTitle("","pageheader","销售系统","由湛江辉迅基于Foxtable开发")
        If e.PostValues.ContainsKey("username") AndAlso e.PostValues.ContainsKey("password")  Then '判断是否是验证失败后的重新登录
            wb.AddTopTips("","toptip1","用户名或密码错误!").msec = 2000 '如果用户通过登录按钮访问,则给用户一个2秒的提示.
        End If
        wb.AddForm("","form1","logon.htm")
        With wb.AddInputGroup("form1","ipg1")
            .AddInput("username","户名","text")
            .AddInput("password","密码","password")
        End With
        With wb.AddButtonGroup("form1","btg1",True)
            .Add("btn1", "登录", "submit")
        End With
    Case "exit.htm" '退出登录
        wb.DeleteCookie("username") '清除cookie中原来的用户名和密码
        wb.DeleteCookie("password")
        wb.InsertHTML("<meta http-equiv='Refresh' c>") '然后直接跳转到登录页面
    Case "", "default.htm" '首页
        wb.AddPageTitle("","pageheader","销售系统","由湛江辉迅基于Foxtable开发")
        With wb.AddGrid("","g1")
            .Add("c1","增加订单", "./images/button.png").Attribute = ""
            .Add("c2","客户管理", "./images/cell.png", "http://www.foxtable.com")
            .Add("c3","销售统计", "./images/toast.png", "http://www.foxtable.com")
            .Add("c4","Dialog", "./images/dialog.png", "http://www.foxtable.com")
            .Add("c5","Progress", "./images/progress.png", "http://www.foxtable.com")
            .Add("c6","Msg", "./images/msg.png", "http://www.foxtable.com")
            .Add("c7","Article", "./images/article.png", "http://www.foxtable.com")
            .Add("c8","ActionSheet", "./images/actionSheet.png", "http://www.foxtable.com")
            .Add("c9","Icons", "./images/icons.png", "http://www.foxtable.com")
            .Add("c10","Panel", "./images/panel.png", "http://www.foxtable.com")
            .Add("c11","Tab", "./images/tab.png", "http://www.foxtable.com")
            .Add("c12","退出", "./images/exit.png", "exit.htm") '退出登录
        End With
End Select
e.WriteString(wb.Build) '生成网页